Split from ch25, SCCP and interprocedural SCCPmain

1 files changed, 2156 insertions, 0 deletions

diff --git a/chapter-interprocedural-sccp/src/main/java/com/seaofnodes/simple/Parser.java b/chapter-interprocedural-sccp/src/main/java/com/seaofnodes/simple/Parser.java
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+++ b/chapter-interprocedural-sccp/src/main/java/com/seaofnodes/simple/Parser.java
@@ -0,0 +1,2156 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.codegen.CodeGen;
+import com.seaofnodes.simple.node.*;
+import com.seaofnodes.simple.type.*;
+import com.seaofnodes.simple.util.Ary;
+import com.seaofnodes.simple.util.Utils;
+import com.seaofnodes.simple.node.ScopeNode.Kind;
+import java.util.*;
+
+/**
+ * The Parser converts a Simple source program to the Sea of Nodes intermediate
+ * representation directly in one pass.  There is no intermediate Abstract
+ * Syntax Tree structure.
+ * <p>
+ * This is a simple recursive descent parser. All lexical analysis is done here as well.
+ */
+public class Parser {
+
+    public static ConstantNode ZERO; // Very common node, cached here
+    public static ConstantNode NIL;  // Very common node, cached here
+    public static XCtrlNode XCTRL;   // Very common node, cached here
+
+    // Compile driver
+    public final CodeGen _code;
+
+    // The Lexer.  Thin wrapper over a byte[] buffer with a cursor.
+    private Lexer _lexer;
+
+    /**
+     * Current ScopeNode - ScopeNodes change as we parse code, but at any point of time
+     * there is one current ScopeNode. The reason the current ScopeNode can change is to do with how
+     * we handle branching. See {@link #parseIf()}.
+     * <p>
+     * Each ScopeNode contains a stack of lexical scopes, each scope is a symbol table that binds
+     * variable names to Nodes.  The top of this stack represents current scope.
+     * <p>
+     * We keep a list of all ScopeNodes so that we can show them in graphs.
+     * @see #parseIf()
+     * @see #_xScopes
+     */
+    public ScopeNode _scope;
+
+    /**
+     * List of keywords disallowed as identifiers
+     */
+    public static final HashSet<String> KEYWORDS = new HashSet<>(){{
+            add("bool");
+            add("break");
+            add("byte");
+            add("continue");
+            add("else");
+            add("f32");
+            add("f64");
+            add("false");
+            add("flt");
+            add("i16");
+            add("i32");
+            add("i64");
+            add("i8");
+            add("if");
+            add("int");
+            add("new");
+            add("null");
+            add("return");
+            add("struct");
+            add("true");
+            add("u1");
+            add("u16");
+            add("u32");
+            add("u8");
+            add("while");
+        }};
+
+    /**
+     * We clone ScopeNodes when control flows branch; it is useful to have
+     * a list of all active ScopeNodes for purposes of visualization of the SoN graph
+     */
+    public final Stack<ScopeNode> _xScopes = new Stack<>();
+
+    ScopeNode _continueScope;
+    ScopeNode _breakScope;      // Merge all the while-breaks here
+    FunNode _fun;               // Current function being parsed
+
+    // Mapping from a type name to a Type.  The string name matches
+    // `type.str()` call.
+    public static HashMap<String, Type> TYPES = defaultTypes();
+
+    // Mapping from a type name to the constructor for a Type.
+    public final HashMap<String, StructNode> INITS;
+
+
+    public Parser(CodeGen code, TypeInteger arg) {
+        _code = code;
+        _scope = new ScopeNode();
+        _continueScope = _breakScope = null;
+        ZERO  = con(TypeInteger.ZERO).keep();
+        NIL  = con(Type.NIL).keep();
+        XCTRL= new XCtrlNode().peephole().keep();
+        TYPES = defaultTypes();
+        INITS = new HashMap<>();
+    }
+
+    @Override
+    public String toString() { return _lexer.toString(); }
+
+    public static HashMap<String, Type> defaultTypes() {
+        return new HashMap<>() {{
+            put("bool",TypeInteger.U1 );
+            put("byte",TypeInteger.U8 );
+            put("f32" ,TypeFloat  .F32);
+            put("f64" ,TypeFloat  .F64);
+            put("flt" ,TypeFloat  .F64);
+            put("i16" ,TypeInteger.I16);
+            put("i32" ,TypeInteger.I32);
+            put("i64" ,TypeInteger.BOT);
+            put("i8"  ,TypeInteger.I8 );
+            put("int" ,TypeInteger.BOT);
+            put("u1"  ,TypeInteger.U1 );
+            put("u16" ,TypeInteger.U16);
+            put("u32" ,TypeInteger.U32);
+            put("u8"  ,TypeInteger.U8 );
+            put("val" ,Type.TOP);    // Marker type, indicates type inference
+            put("var" ,Type.BOTTOM); // Marker type, indicates type inference
+        }};
+    }
+
+    // Debugging utility to find a Node by index
+    public Node f(int nid) { return _code.f(nid); }
+
+    private Node ctrl() { return _scope.ctrl(); }
+    private <N extends Node> N ctrl(N n) { return _scope.ctrl(n); }
+
+    public void parse() {
+        // Graph callbacks during scope setup need a source position.
+        _lexer = new Lexer(sys.SYS);
+
+        _scope.define(ScopeNode.CTRL, Type.CONTROL   , false, null, _lexer);
+        _scope.define(ScopeNode.MEM0, TypeMem.BOT    , false, null, _lexer);
+        _scope.define(ScopeNode.ARG0, TypeInteger.BOT, false, null, _lexer);
+
+        ctrl(XCTRL);
+        _scope.mem(con(TypeMem.BOT));
+
+        // Parse the sys import
+        while( !_lexer.isEOF() ) {
+            parseStatement();
+            _lexer.skipWhiteSpace();
+        }
+
+        // Reset lexer for program text
+        _lexer = new Lexer(_code._src);
+        _xScopes.push(_scope);
+
+        // Parse whole program, as-if function header "{ int arg -> body }"
+        parseFunctionBody( _code._main,loc(),"arg");
+
+        // Kill an empty default main.  Keep only if it was explicitly defined
+        // (programmer asked for a "main") or it has stuff (i.e. beginner
+        // default main).
+        FunNode main = _code.link(_code._main);
+        StopNode stop = _code._stop;
+        // Gather an explicit main
+        FunNode xmain = null;
+        for( Node n : stop._inputs )
+            if( n instanceof ReturnNode ret && "main".equals(ret.fun()._name) )
+                if( xmain != null ) throw Utils.TODO();
+                else xmain = ret.fun();
+
+        if( main.ret().expr()._type==Type.TOP && main.uctrl()==null ) {
+            // Kill an empty default main; so it does not attempt to put a
+            // "main" in any final ELF file
+            main.setDef(1,XCTRL); // Delete default start input
+            stop.delDef(stop._inputs.find(main.ret()));
+            if( xmain != null )
+                _code.setMain(xmain);
+
+        } else {
+            // We have a non-empty default main.
+            if( xmain != null )
+                // Found an explicit "main" AND we have a default "main"
+                throw error("Cannot define both an explicit main and a default main");
+            main._name = "main";
+        }
+
+        if( !_lexer.isEOF() ) throw _errorSyntax("unexpected");
+
+        // Clean up and reset
+        _xScopes.pop();
+        _scope.kill();
+        for( StructNode init : INITS.values() )
+            init.unkeep().kill();
+        INITS.clear();
+        stop.peephole();
+    }
+
+    /**
+     *  Parses a function body, assuming the header is parsed.
+     */
+    private ReturnNode parseFunctionBody( TypeFunPtr sig, Lexer loc, String... ids) {
+        return parseFunctionBody(sig, loc, null, ids);
+    }
+
+    private ReturnNode parseFunctionBody( TypeFunPtr sig, Lexer loc, java.util.BitSet finals, String... ids) {
+        // If this is a method, record & restore the existing struct fields,
+        // which are also the struct initializers.  The method might update
+        // mutable fields, so when the function parse is done reset back to
+        // pre-function-parse values.
+        Node[] preParse = new Node[_scope.nIns()];
+        for( int i=0; i<_scope.nIns(); i++ )
+            preParse[i] = _scope.in(i)==null ? null : _scope.in(i).keep();
+
+        // Stack parser state on the local Java stack, and unstack it later
+        FunNode oldfun  = _fun;
+        ScopeNode breakScope = _breakScope; _breakScope = null;
+        ScopeNode continueScope = _continueScope; _continueScope = null;
+
+        FunNode fun = _fun = (FunNode)peep(new FunNode(loc(),sig,_nestedType,null,_code._start));
+        // Once the function header is available, install in linker table -
+        // allowing recursive functions.  Linker matches on declared args and
+        // exact fidx, and ignores the return (because the fidx will only match
+        // the exact single function).
+        _code.link(fun);
+
+        Node rpc = new ParmNode("$rpc",0,TypeRPC.BOT,fun,con(TypeRPC.BOT)).peephole();
+
+        // Build a multi-exit return point for all function returns
+        RegionNode r = new RegionNode( null,null,null).init();
+        assert r.inProgress();
+        PhiNode rmem = new BulkMemPhiNode(ScopeNode.MEM0,r,null).init();
+        PhiNode rrez = new PhiNode(ScopeNode.ARG0,Type.BOTTOM,r,null).init();
+        ReturnNode ret = new ReturnNode(r, rmem, rrez, rpc, fun).init();
+        fun.setRet(ret);
+        assert ret.inProgress();
+        _code._stop.addDef(ret);
+
+
+        // Pre-call the function from Start, with worse-case arguments.  This
+        // represents all the future, yet-to-be-parsed functions calls and
+        // external calls.
+        _scope.push(new Kind.Func());
+        ctrl(fun);              // Scope control from function
+        // Unknown callers supply whole memory; field aliases are discovered lazily.
+        _scope.mem(new ParmNode(ScopeNode.MEM0,1,TypeMem.BOT,fun,con(TypeMem.BOT)).peephole());
+        // All args, "as-if" called externally
+        for( int i=0; i<ids.length; i++ ) {
+            Type t = sig.arg(i);
+            _scope.define(ids[i], t, finals==null ? t instanceof TypeNil : finals.get(i), new ParmNode(ids[i],i+2,t,fun,con(t)).peephole(), loc);
+        }
+
+        // Parse the body
+        Node last=ZERO;
+        while (!peek('}') && !_lexer.isEOF())
+            last = parseStatement();
+
+        // Last expression is the return except for the top-level main
+        if( ctrl()._type==Type.CONTROL )
+            if( fun.sig() != _code._main )
+                fun.addReturn(ctrl(), _scope.mem(), last);
+            else {
+                fun.setDef(1,XCTRL); // Kill default main
+                _code.addAll(fun._outputs);
+            }
+
+        // Pop off the inProgress node on the multi-exit Region merge
+        assert r.inProgress();
+        r   ._inputs.pop();
+        rmem._inputs.pop();
+        rrez._inputs.pop();
+        r._loc = loc();         // Final position
+        assert !r.inProgress();
+
+        // Force peeps, which have been avoided due to inProgress
+        ret.setDef(1,rmem.peephole());
+        ret.setDef(2,rrez.peephole());
+        ret.setDef(0,r.peephole());
+        ret = (ReturnNode)ret.peephole();
+
+        // Function scope ends
+        _scope.pop();
+        _fun = oldfun;
+        _breakScope = breakScope;
+        _continueScope = continueScope;
+
+        // Reset all fields to pre-parse days
+        for( int i=0; i<preParse.length; i++ )
+            _scope.setDef(i,preParse[i]==null ? null : preParse[i].unkeep());
+
+        return ret;
+    }
+
+    /**
+     * Parses a block
+     *
+     * <pre>
+     *     '{' statements '}'
+     * </pre>
+     * Does not parse the opening or closing '{}'
+     * @return a {@link Node} or {@code null}
+     */
+    private Node parseBlock(Kind kind) {
+        // Enter a new scope
+        _scope.push(kind);
+        Node last = ZERO;
+        while (!peek('}') && !_lexer.isEOF())
+            last = parseStatement();
+        // Exit scope
+        last.keep();
+        _scope.pop();
+        return last.unkeep();
+    }
+
+    /**
+     * Parses a statement
+     *
+     * <pre>
+     *     returnStatement | declStatement | blockStatement | ifStatement | expressionStatement
+     * </pre>
+     * @return a {@link Node} or {@code null}
+     */
+    private Node parseStatement() {
+        if(      matchx("return")  ) return parseReturn();
+        else if (matchx("if")      ) return parseIf();
+        else if (matchx("while")   ) return parseWhile();
+        else if (matchx("for")     ) return parseFor();
+        else if (matchx("break")   ) return parseBreak();
+        else if (matchx("continue")) return parseContinue();
+        else if (matchx("struct")  ) return parseStruct();
+        else if (matchx(";")       ) return null; // Empty statement
+        // Break ambiguity around leading function types and starting a block
+        else if (peek('{') && !isTypeFun() ) {
+            match("{");
+            return require(parseBlock(new Kind.Block()),"}");
+        }
+        // Declaration or normal assignment/expression
+        else return parseDeclarationStatement();
+    }
+
+    /**
+     * Parses a while statement
+     *
+     * <pre>
+     *     while ( expression ) statement
+     * </pre>
+     * @return a {@link Node}, never {@code null}
+     */
+    private Node parseWhile() {
+        require("(");
+        return parseLooping(false);
+    }
+
+
+    /**
+     * Parses a for statement
+     *
+     * <pre>
+     *     for( var x=init; test; incr ) body
+     * </pre>
+     * @return a {@link Node}, never {@code null}
+     */
+    private Node parseFor() {
+        // {   var x=init,y=init,...;
+        //     while( test ) {
+        //         body;
+        //         next;
+        //     }
+        // }
+        require("(");
+        _scope.push(new Kind.Block()); // Scope for the index variables
+        if( !match(";") )        // Can be empty init "for(;test;next) body"
+            parseDeclarationStatement(); // Non-empty init
+        Node rez = parseLooping(true);
+        _scope.pop();           // Exit index variable scope
+        return rez;
+    }
+
+    // Shared by `for` and `while`
+    private Node parseLooping( boolean doFor ) {
+
+        var savedContinueScope = _continueScope;
+        var savedBreakScope    = _breakScope;
+
+        // Loop region has two control inputs, the first is the entry
+        // point, and second is back edge that is set after loop is parsed
+        // (see end_loop() call below).  Note that the absence of back edge is
+        // used as an indicator to switch off peepholes of the region and
+        // associated phis; see {@code inProgress()}.
+
+        ctrl(new LoopNode(loc(),ctrl()).peephole()); // Note we set back edge to null here
+
+        // At loop head, we clone the current Scope (this includes all
+        // names in every nesting level within the Scope).
+        // We create phis eagerly for all the names we find, see dup().
+
+        // Save the current scope as the loop head
+        ScopeNode head = _scope.keep();
+        // Clone the head Scope to create a new Scope for the body.
+        // Create phis eagerly as part of cloning
+        _xScopes.push(_scope = _scope.dup(true)); // The true argument triggers creating phis
+
+        // Parse predicate
+        var pred = peek(';') ? con(1) : parseAsgn();
+        require( doFor ? ";" : ")" );
+
+        // IfNode takes current control and predicate
+        Node ifNode = new IfNode(ctrl(), pred.keep()).peephole();
+        // Setup projection nodes
+        Node ifT = new CProjNode(ifNode.  keep(), 0, "True" ).peephole().keep();
+        Node ifF = new CProjNode(ifNode.unkeep(), 1, "False").peephole();
+
+        // for( ;;next ) body
+        int nextPos = -1, nextEnd = -1;
+        if( doFor ) {
+            // Skip the next expression and parse it later
+            nextPos = pos();
+            skipAsgn();
+            nextEnd = pos();
+            require(")");
+        }
+
+        // Clone the body Scope to create the break/exit Scope which accounts for any
+        // side effects in the predicate.  The break/exit Scope will be the final
+        // scope after the loop, and its control input is the False branch of
+        // the loop predicate.  Note that body Scope is still our current scope.
+        ctrl(ifF);
+        _xScopes.push(_breakScope = _scope.dup());
+        _breakScope.addGuards(ifF,pred,true); // Up-cast predicate
+
+        // No continues yet
+        _continueScope = null;
+
+        // Parse the true side, which corresponds to loop body
+        // Our current scope is the body Scope
+        ctrl(ifT.unkeep());     // set ctrl token to ifTrue projection
+        _scope.addGuards(ifT,pred.unkeep(),false); // Up-cast predicate
+        parseStatement().isKill();                 // Parse loop body
+        _scope.removeGuards(ifT);
+
+        // Merge the loop bottom into other continue statements
+        if (_continueScope != null) {
+            _continueScope = jumpTo(_continueScope);
+            _scope.kill();
+            _scope = _continueScope;
+        }
+
+        // Now append the next code onto the body code
+        if( doFor ) {
+            int old = pos(nextPos);
+            if( !peek(')') )
+              parseAsgn();
+            if( pos() != nextEnd )
+                throw errorSyntax( "Unexpected code after expression" );
+            pos(old);
+        }
+
+        // The true branch loops back, so whatever is current _scope.ctrl gets
+        // added to head loop as input.  endLoop() updates the head scope, and
+        // goes through all the phis that were created earlier.  For each phi,
+        // it sets the second input to the corresponding input from the back
+        // edge.  If the phi is redundant, it is replaced by its sole input.
+        var exit = _breakScope;
+        head.endLoop(_scope, exit);
+        head.unkeep().kill();
+
+        _xScopes.pop();       // Cleanup
+        _xScopes.pop();       // Cleanup
+
+        _continueScope = savedContinueScope;
+        _breakScope = savedBreakScope;
+
+        // At exit the false control is the current control, and
+        // the scope is the exit scope after the exit test.
+        // During sys parsing, there is no xscope here.
+        if( !_xScopes.isEmpty() ) {
+            _xScopes.pop();
+            _xScopes.push( exit );
+        }
+        _scope = exit;
+        return ZERO;
+    }
+
+    private ScopeNode jumpTo(ScopeNode toScope) {
+        ScopeNode cur = _scope.dup();
+        ctrl(XCTRL); // Kill current scope
+        // Prune nested lexical scopes that have depth > than the loop head
+        // We use _breakScope as a proxy for the loop head scope to obtain the depth
+        while( cur.depth() > _breakScope.depth() )
+            cur.pop();
+        // If this is a continue then first time the target is null
+        // So we just use the pruned current scope as the base for the
+        // "continue"
+        if( toScope == null )
+            return cur;
+        // toScope is either the break scope, or a scope that was created here
+        assert toScope.depth() <= _breakScope.depth();
+        toScope.ctrl(toScope.mergeScopes(cur,loc()).peephole());
+        return toScope;
+    }
+
+    private void checkLoopActive() { if (_breakScope == null) throw error("No active loop for a break or continue"); }
+
+    private Node parseContinue() { checkLoopActive(); _continueScope = require(jumpTo( _continueScope ),";"); return ZERO; }
+    private Node parseBreak   () {
+        checkLoopActive();
+        // At the time of the break, and loop-exit conditions are only valid if
+        // they are ALSO valid at the break.  It is the intersection of
+        // conditions here, not the union.
+        _breakScope.removeGuards(_breakScope.ctrl());
+        _breakScope = require(jumpTo(_breakScope ),";");
+        _breakScope.addGuards(_breakScope.ctrl(), null, false);
+        return ZERO;
+    }
+
+    // Look for an unbalanced `)`, skipping balanced
+    private void skipAsgn() {
+        int paren=0;
+        while( true )
+            // Next X char handles skipping complex comments
+            switch( _lexer.nextXChar() ) {
+            case Character.MAX_VALUE:
+                throw Utils.TODO();
+            case ')':
+                if( --paren<0 ) {
+                    posT( pos() - 1 );
+                    return; // Leave the `)` behind
+                }
+                break;
+            case '(': paren ++; break;
+            default: break;
+            }
+    }
+
+
+    /**
+     * Parses a statement
+     *
+     * <pre>
+     *     if ( expression ) statement [else statement]
+     * </pre>
+     * @return a {@link Node}, never {@code null}
+     */
+    private Node parseIf() {
+        // Parse predicate
+        require("(");
+        var pred = require(parseAsgn(), ")");
+        return parseTrinary(pred,"else");
+    }
+
+    // Parse a conditional expression, merging results.
+    private Node parseTrinary( Node pred, String fside ) {
+        // IfNode takes current control and predicate
+        pred.keep();
+        Node ifNode = new IfNode(ctrl(), pred).peephole();
+        // Setup projection nodes
+        Node ifT = new CProjNode(ifNode.  keep(), 0, "True" ).peephole().keep();
+        Node ifF = new CProjNode(ifNode.unkeep(), 1, "False").peephole().keep();
+        // In if true branch, the ifT proj node becomes the ctrl
+        // But first clone the scope and set it as current
+        ScopeNode fScope = _scope.dup(); // Duplicate current scope
+        fScope.ctrl(ifF);       // The pending arm already starts at False
+        _xScopes.push(fScope); // For graph visualization we need all scopes
+
+        // Parse the true side
+        ctrl(ifT.unkeep());     // set ctrl token to ifTrue projection
+        _scope.addGuards(ifT,pred,false); // Up-cast predicate
+        // Parse true-side flavor
+        Node lhs = switch( fside ) {
+        case "else" -> parseStatement(); // if( pred )  stmts;
+        case ":"    -> parseAsgn();      //     pred ?  asgn;
+        case "&&"   -> parseLogical();   //     pred && expr
+        case "||"   -> pred;             //     pred || expr_is_ignored
+        default     -> throw Utils.TODO();
+        };
+        lhs.keep();
+        _scope.removeGuards(ifT);
+
+        // See if a one-sided def was made: "if(pred) int x = 1;" and throw.
+        // See if any forward-refs were made, and copy them to the other side:
+        // "pred ? n*fact(n-1) : 1"
+        fScope.balanceIf(_scope);
+
+        ScopeNode tScope = _scope;
+
+        // Parse the false side
+        _scope = fScope;        // Restore scope, then parse else block if any
+        ifF.unkeep();           // fScope already owns the false control
+        // Up-cast predicate, even if not else clause, because predicate can
+        // remain true if the true clause exits: `if( !ptr ) return 0; return ptr.fld;`
+        _scope.addGuards(ifF,pred,true);
+        // Parse false-side flavor
+        boolean doRHS = false;  // RHS is optional for if/else and trinary
+        Node rhs = switch( fside ) {
+        case "else" -> (doRHS=match(fside)) ? parseStatement() : con(lhs._type.makeZero());
+        case ":"    -> (doRHS=match(fside)) ? parseAsgn()      : con(lhs._type.makeZero());
+        case "&&"   -> rhs = pred;
+        case "||"   -> rhs = parseLogical();
+        default     -> throw Utils.TODO();
+        };
+        rhs.keep();
+        _scope.removeGuards(ifF);
+        if( doRHS || fside.equals("||") )
+            fScope = _scope;
+        pred.unkeep();
+
+        // Check the trinary widening int/flt
+        if( !fside.equals("else") ) {
+            rhs = widenInt( rhs.unkeep(), lhs._type ).keep();
+            lhs = widenInt( lhs.unkeep(), rhs._type ).keep();
+        }
+
+        _scope = tScope;
+        _xScopes.pop();       // Discard pushed from graph display
+        // See if a one-sided def was made: "if(pred) int x = 1;" and throw.
+        // See if any forward-refs were made, and copy them to the other side:
+        // "pred ? n*fact(n-1) : 1"
+        tScope.balanceIf(fScope);
+
+        // Merge results
+        RegionNode r = ctrl(tScope.mergeScopes(fScope,loc()));
+        Node ret = peep(new PhiNode("",lhs._type.meet(rhs._type).glb(false),r,lhs.unkeep(),rhs.unkeep()));
+        // Immediately fail e.g. `arg ? 7 : ptr`
+        ParseException err;
+        if( !fside.equals("else") && (err=ret.err()) !=null )  throw err;
+        r.peephole();
+        return ret;
+    }
+
+    /**
+     * Parses a return statement; "return" already parsed.
+     * The $ctrl edge is killed.
+     *
+     * <pre>
+     *     'return' expr ;
+     * </pre>
+     * @return an expression {@link Node}, never {@code null}
+     */
+    private Node parseReturn() {
+        var expr = require(parseAsgn(), ";");
+        // Force the lazy whole-memory Phi before closing this exit.
+        _fun.addReturn(ctrl(), _scope.mem(), expr);
+        ctrl(XCTRL);            // Kill control
+        return expr;
+    }
+
+
+
+    /** Parse: [name '='] expr
+     */
+    private Node parseAsgn() {
+        int old = pos();
+        String name = _lexer.matchId();
+        int old_pre_equals = pos();
+        // Just a plain expression, no assignment.
+        // Distinguish `var==expr` from `var=expr`
+        if( name==null || KEYWORDS.contains(name) || !matchOpx('=','=') )
+            {  pos(old);  return parseExpression();  }
+
+        // Find variable to update
+        Var def = _scope.lookup(name);
+        if( def==null )
+            throw error("Undefined name '" + name + "'");
+
+        // If a method var, allow nested blocks and methods, but not fcns or other structs.
+        // Else safety check for accessing fields out of function scope.
+        if( instance(def) ) {
+            pos(old_pre_equals);  // setup for `self.name = expr`
+            Node self = _scope.in(_scope.lookup("self")); // Insert self reference
+            return parsePostfixName(self,name);
+        }
+
+        // TOP fields are for late-initialized fields; these have never
+        // been written to, and this must be the final write.  Other writes
+        // outside the constructor need to check the final bit.
+        if( _scope.in(def._idx)._type!=Type.TOP && def._final &&
+            // Inside an allocation, final assign is OK, outside nope.
+            // The alloc() call added the allocation scope
+            !_scope.canInit(def) )
+            throw error("Cannot reassign final '"+name+"'");
+
+        // Parse assignment expression
+        Node expr = parseAsgn();
+
+        // Lift expression, based on type
+        Node lift = liftExpr(expr.keep(), def.type(), true);
+        // Update
+        _scope.update(name,lift);
+        // Return un-lifted expr
+        return expr.unkeep();
+    }
+
+    // Apply declared access permissions; widen floats and narrow integers.
+    // Early error if types do not match variable.
+    private Node liftExpr( Node expr, Type t, boolean isLoad ) {
+        if( expr._type instanceof TypeMemPtr tmp && TYPES.get(tmp._obj._name).isFRef() )
+            throw error("Must define forward ref "+tmp._obj._name);
+        // Read-only access is deep; a fixed binding alone does not remove access.
+        if( t instanceof TypeMemPtr tmp && tmp.isFinal() ) {
+            expr = peep(new ReadOnlyNode(expr));
+        }
+        if( !expr._type.accessISA(t) )
+            throw error("Type " + expr._type.str() + " is not of declared type " + t.str());
+        // Auto-widen array to i64 (cast ptr to raw int bits)
+        if( t == TypeInteger.BOT && expr._type instanceof TypeMemPtr tmp && tmp._obj.isAry() )
+            expr = peep(new AddNode(peep(new CastNode(t,ctrl(),expr)),off(tmp._obj,"[]")));
+        // Auto-widen int to float
+        expr = widenInt( expr, t );
+        // Auto-narrow wide ints to narrow ints.  For loads, emit code to force
+        // the loaded value to match the declared sign/zero bits.  For stores,
+        // just force the type, acting "as if" the store silently truncates.
+        if( expr._type instanceof TypeFloat && t instanceof TypeInteger )
+            expr = peep(new ToIntegerNode(expr));
+        Type et = expr._type;
+        if( isLoad ) { expr = zsMask(expr,t); et = expr._type; }
+        else if( et instanceof TypeInteger && t instanceof TypeInteger ) et=t;
+
+        // Type is sane
+        if( et!=Type.BOTTOM && (!et.shallowISA(t) || !et.accessISA(t)) )
+            expr = peep(new CastNode(t.isConstant() ? t : t.widen(),null,expr));
+        return expr;
+    }
+
+    private Node widenInt( Node expr, Type t ) {
+        return (expr._type instanceof TypeInteger || expr._type==Type.NIL) && t instanceof TypeFloat
+            ? peep(new ToFloatNode(expr)) : expr;
+    }
+
+    /**
+     * Parse declaration or expression statement
+     * declStmt = type var['=' exprAsgn][, var['=' exprAsgn]]* ';' | exprAsgn ';'
+     * <p>
+     * exprAsgn = var '=' exprAsgn | expr
+     */
+    private Node parseDeclarationStatement() {
+        int old = pos();
+        Type t = type();
+        if( peek('.') )         // Ambiguity static vars: "type.var", parse as expression
+            { pos(old); t=null; }
+        if( t == null )
+            return require(parseAsgn(),";");
+
+        // now parse var['=' asgnexpr] in a loop
+        Node n = parseDeclaration(t);
+        while( match(",") )
+            n = parseDeclaration(t);
+        return require(n,";");
+    }
+
+    // Widen a reassignable binding without discarding the initializer's
+    // permissions. Lattice glb includes readonly memory and is too broad here.
+    private Type inferredType(Type t) {
+        if( t instanceof TypeMemPtr tmp ) {
+            if( tmp._obj.isAry() ) {
+                Type elem = tmp._obj._fields[1]._t;
+                if( elem instanceof TypeConAry )
+                    elem = ((TypeMemPtr)TYPES.get(tmp._obj._name))._obj._fields[1]._t;
+                return typeAry(elem,tmp._obj._fields[1]._final).withAccess(tmp._ro).makeNullable();
+            }
+            Type base = TYPES.get(tmp._obj._name);
+            TypeMemPtr ptr = (TypeMemPtr)base;
+            return ptr.withAccess(tmp._ro).makeNullable();
+        }
+        return t.glb(false);
+    }
+
+    // The binding modifier sits immediately before the name. It never
+    // changes permissions on the referenced object.
+    private boolean bindingFinal(Type t) {
+        if( match("!") ) return false;
+        if( match("~") ) return true;
+        return t==Type.TOP || t instanceof TypeNil;
+    }
+
+    /** Parse final: [!|~]var['=' asgn]
+     */
+    private Node parseDeclaration(Type t) {
+        assert t!=null;
+        // Has var/val instead of a user-declared type
+        boolean inferType = t==Type.TOP || t==Type.BOTTOM;
+        boolean xfinal = bindingFinal(t);
+        Lexer loc = loc();
+        String name = requireId();
+        // Optional initializing expression follows
+        boolean fld_final = false; // Fixed field independent of pointee access
+        boolean initialized = match("=");
+        Node expr;
+        if( initialized ) {
+            expr = isExternDecl()
+                ? externDecl(name,t)
+                : parseAsgn();
+            // var/val, then type comes from expression
+            if( inferType ) {
+                if( expr._type==Type.NIL )
+                    throw error("a not-null/non-zero expression");
+                t = expr._type;
+                if( !xfinal ) t = inferredType(t);  // Widen if not final
+            }
+            // expr is a constant function
+            if( t instanceof TypeFunPtr && expr._type instanceof TypeFunPtr tfp && tfp.isConstant() ) {
+                if( expr instanceof ExternNode ) t = expr._type; // Upgrade declared type to exact function
+                else _code.link(tfp).setName(name); // Assign debug name to Simple function
+            }
+
+        } else {
+            // Need an expression to infer the type.
+            // Also, if not-null then need an initializing expression.
+            // Allowed in a class def, because type/init will happen in the constructor.
+            if( (inferType || (t instanceof TypeNil tn && !tn.nullable() )) && !_scope.inConstructor() )
+                throw errorSyntax("=expression");
+            // Initial value for uninitialized struct fields.
+            expr = switch( t ) {
+                // Nullable pointers get a NIL; not-null get a TOP which
+                // signals that they *must* be initialized in the constructor.
+            case TypeNil tn -> tn.nullable() ? NIL : con(Type.TOP);
+            case TypeInteger ti -> xfinal ? con(Type.TOP) : ZERO;
+            case TypeFloat tf -> con(xfinal ? Type.TOP : TypeFloat.FZERO);
+            // Bottom signals type inference: they must be initialized in
+            // the constructor and that's when we'll discover the type.
+            case Type tt -> { assert tt==Type.BOTTOM; yield con(tt); }
+            };
+            // Nullable fields are set in the constructor, but remain shallow final.
+            // e.g. final pointer to a r/w array
+            if( t instanceof TypeNil tn && !tn.nullable() && xfinal )
+                fld_final = true;
+        }
+
+        // Lift expression, based on type
+        Node lift = liftExpr(expr, t, true);
+
+        // Lift type to the declaration.  This will report as an error later if
+        // we cannot lift the type.
+        if( !lift._type.isa(t) )
+            lift = peep(new CastNode(t.widen(),null,lift));
+        // Define a new name
+        if( !_scope.define(name,t,xfinal || fld_final,lift, loc) )
+            throw error("Redefining name '" + name + "'", loc);
+        _scope.lookup(name)._init = initialized;
+        return lift;
+    }
+
+
+
+    /**
+     * Parse a struct declaration, and return the following statement.
+     * Structs cannot be redefined, but can be nested.
+     *
+     * @return zero
+     */
+    private String _nestedType;
+    private Node parseStruct() {
+        // "struct" already parsed, so expect the struct name next.
+        String old = _nestedType;
+        String typeName = requireId();
+        if( old!=null ) typeName = old+"."+typeName;
+        _nestedType = typeName;
+        // New declared or forward-ref type
+        TypeStruct ts = TYPES.get(typeName) instanceof TypeMemPtr tmp ? tmp._obj : TypeStruct.open(typeName);
+        TYPES.put(typeName,TypeMemPtr.make(ts));
+
+        // A Block scope parse, and inspect the scope afterward for fields.
+        _scope.push(new Kind.Define(TypeMemPtr.make(ts)));
+        require("{");
+        int lexlen = _scope._kinds.last()._lexSize, nvar=lexlen;
+        while (!peek('}') && !_lexer.isEOF()) {
+            parseStatement().isKill();
+            while( nvar < _scope._vars._len ) {
+                Var v = _scope.var(nvar++);
+                if( !v.isFRef() ) {
+                    ts = ts.add( Field.make( v._name, v.type(), _code.getALIAS(), v._final, v._final && v._init && _scope.in( v._idx )._type != Type.TOP ) );
+                    TYPES.put( typeName, TypeMemPtr.make( ts ) );
+                }
+            }
+        }
+
+        // Count struct declarations
+        int varlen = _scope._vars._len;
+        ts = ts.close();
+        TYPES.put(typeName,TypeMemPtr.make(ts));
+
+        // Generate an initializing struct
+        StructNode s = new StructNode(ts);
+        for( int i=lexlen; i<varlen; i++ )
+            if( !_scope.var(i).isFRef() ) // Promote to outer scope, not defined here
+                s.addDef(_scope.in(i)); // Keep the program code to generate instance
+
+        // Save instance default constructor
+        s.setType(s.compute()); // Do not call peephole, in case the entire struct is a big plain constant
+        INITS.put(typeName,s.keep());
+
+        // Having finalized the struct, upgrade all the 'self' pointers
+        for( Node n : s._inputs )
+            if( n._type instanceof TypeFunPtr tfp && _code.link(tfp) instanceof FunNode fun )
+                _code.addAll( fun._outputs );
+
+
+        // Done with struct/block scope
+        _nestedType = old;
+        require("}");
+        require(";");
+        _scope.pop();
+        return ZERO;
+    }
+
+
+    // Parse and return a type or null.  Valid types always are followed by an
+    // 'id' which the caller must parse.  This lets us distinguish forward ref
+    // types (which ARE valid here) from local vars in an (optional) forward
+    // ref type position.
+
+    // t = int|i8|i16|i32|i64|u8|u16|u32|u64|byte|bool | flt|f32|f64 | val | var | struct[?]
+    private Type type() {
+        int old1 = pos();
+        boolean writable = match("!");
+        boolean readonly = !writable && match("~");
+        // Only type with a leading `{` is a function pointer...
+        if( peek('{') ) return typeFunPtr();
+
+        // Otherwise you get a type name
+        String tname = _lexer.matchId();
+        if( tname==null ) return posT(old1);
+
+        // Convert the type name to a type.
+        Type t0 = TYPES.get(tname);
+        // No new types as keywords
+        if( t0 == null && KEYWORDS.contains(tname) )
+            return posT(old1);
+        if( t0 == Type.BOTTOM || t0 == Type.TOP ) return t0; // var/val type inference
+
+        // Check for subtype.
+        while( true ) {
+            int old2 = pos();
+            if( !match(".") )  break;
+            String sname = _lexer.matchId();
+            if( sname==null ) { pos(old2); break; }
+            String tsname = tname+"."+sname;
+            t0 = TYPES.get(tsname);
+            if( t0==null ) { pos(old2); t0 = TYPES.get(tname); break; }
+            tname = tsname;
+        }
+
+        // Still no type found?  Assume forward reference
+        Type t1 = t0 == null ? TypeMemPtr.make(TypeStruct.open(tname)) :t0; // Null: assume a forward ref type
+        // A qualifier before the name applies to the struct reference, not
+        // to an enclosing array. Arrays have their own [] / [~] qualifier.
+        if( t1 instanceof TypeMemPtr tmp ) {
+            if( readonly || !writable ) t1 = tmp.makeRO();
+        } else if( writable || readonly )
+            return posT(old1);
+
+        // Nest arrays and '?' as needed
+        Type t2 = t1;
+        while( true ) {
+            if( match("?") ) {
+                if( !(t2 instanceof TypeMemPtr tmp) )
+                    throw error("Type "+t0+" cannot be null");
+                if( tmp.nullable() ) throw error("Type "+t2+" already allows null");
+                t2 = tmp.makeNullable();
+            } else if( match("[~]") ) {
+                t2 = typeAry(t2,true).makeRO();
+            } else if( match("[]") ) {
+                t2 = typeAry(t2,false);
+            } else
+                break;
+        }
+
+        // Check no forward ref
+        if( t0 != null ) return t2;
+        // Check valid forward ref, after parsing all the type extra bits.
+        // Cannot check earlier, because cannot find required 'id' until after "[]?" syntax
+        int old2 = pos();
+        if( !match("!") ) match("~");
+        String id = _lexer.matchId();
+        if( !(peek(',') || peek(';') || match("->")) || id==null )
+            return posT(old1);  // Reset lexer to reparse
+        pos(old2);              // Reset lexer to reparse
+        // Yes a forward ref, so declare it
+        TYPES.put(tname,((TypeMemPtr)t1).withAccess(false));
+        // Return the (array, final) type
+        return t2;
+    }
+
+    // Make an array type of t
+    private TypeMemPtr typeAry( Type t, boolean efinal ) {
+        if( t instanceof TypeMemPtr tmp && tmp.notNull()  )
+            throw error("Arrays of reference types must always be nullable");
+        String tname = "[]"+t.str();
+        TypeMemPtr ta = (TypeMemPtr)TYPES.get(tname);
+        if( ta==null )
+            // Remember final version
+            TYPES.put(tname, ta = TypeMemPtr.make( TypeStruct.makeAry(tname,TypeInteger.U32,_code.getALIAS(),t,_code.getALIAS(),true) ));
+        // Reuse aliases, but preserve this occurrence's element permissions.
+        TypeStruct ary = ta._obj;
+        return TypeMemPtr.make(TypeStruct.makeAry(tname,TypeInteger.U32,ary._fields[0]._alias,t,ary._fields[1]._alias,efinal));
+    }
+
+    // A function type is `{ type... -> type }` or `{ type }`.
+    private Type typeFunPtr() {
+        int old = pos();        // Record lexer position
+        match("{");             // Skip already-peeked '{'
+        Type t0 = type();       // Either return or first arg
+        if( t0==null ) return posT(old); // Not a function
+        if( match("}") )                 // No-arg function { -> type }
+            return TypeFunPtr.make(match("?"),false,TypeFunPtr.TEMPTY,t0);
+        Ary<Type> ts = new Ary<>(Type.class);
+        ts.push(t0);            // First argument
+        while( true ) {
+            if( match("->") ) { // End of arguments, parse return
+                Type ret = type();
+                if( ret==null || !match("}") )
+                    return posT(old); // Not a function
+                return TypeFunPtr.make(match("?"),false,ts.asAry(),ret);
+            }
+            Type t1 = type();
+            if( t1==null ) return posT(old); // Not a function
+            ts.push(t1);
+        }
+    }
+
+    // True if a TypeFunPtr, without advancing parser
+    private boolean isTypeFun() {
+        int old = pos();
+        if( typeFunPtr()==null ) return false;
+        pos(old);
+        return true;
+    }
+
+    /**
+     * Parse an expression of the form:
+     *
+     * <pre>
+     *     expr : bitwise [? expr [: expr]]
+     * </pre>
+     * @return an expression {@link Node}, never {@code null}
+     */
+    private Node parseExpression() {
+        Node expr = parseLogical();
+        return match("?") ? parseTrinary(expr,":") : expr;
+    }
+
+    /**
+     * Parse an bitwise expression
+     *
+     * <pre>
+     *     bitwise : compareExpr (('&' | '|' | '^') compareExpr)*
+     * </pre>
+     * @return a bitwise expression {@link Node}, never {@code null}
+     */
+
+    private Node parseLogical() {
+        Node lhs = parseBitwise();
+        while (true) {
+            if( false ) ;
+            else if( match("&&") ) lhs = parseTrinary(lhs, "&&");
+            else if( match("||") ) lhs = parseTrinary(lhs, "||");
+            else break;
+        }
+        return lhs;
+    }
+
+    private Node parseBitwise() {
+        Node lhs = parseEquality();
+        while( true ) {
+            if( false ) ;
+            else if( matchOp('&') ) lhs = new AndNode(loc(),lhs,null);
+            else if( matchOp('|') ) lhs = new  OrNode(loc(),lhs,null);
+            else if( match  ("^") ) lhs = new XorNode(loc(),lhs,null);
+            else break;
+            lhs.setDef(2,parseEquality());
+            lhs = peep(lhs);
+        }
+        return lhs;
+    }
+
+
+
+    /**
+     * Parse an eq/ne expression
+     */
+    private Node parseEquality() {
+        Node lhs = parseComparison();
+        while( true ) {
+            boolean eq = false;
+            if( match("==") ) eq = true;
+            else if( !match("!=") ) break;
+            lhs.keep();
+            Node rhs = parseComparison();
+            lhs = peep(new BoolNode.EQ(lhs.unkeep(),rhs).widen());
+            if( !eq ) lhs = peep(new NotNode(lhs));
+        }
+        return lhs;
+    }
+
+    /**
+     * Parse an expression of the form:
+     *
+     * <pre>
+     *     expr : shiftExpr < shiftExpr <= shiftExpr...
+     *     expr : shiftExpr > shiftExpr >= shiftExpr...
+     * </pre>
+     * @return an comparator expression {@link Node}, never {@code null}
+     */
+    private Node parseComparison() {
+        Node lhs = parseShift();
+        int dir = 0;
+
+        while( true ) {
+            int dir0;
+            if( false ) ;
+            else if( match("<=" ) ) dir0 = -1;
+            else if( match(">=" ) ) dir0 = -2;
+            else if( match("<"  ) ) dir0 =  1;
+            else if( match(">"  ) ) dir0 =  2;
+            else break;
+            lhs.keep();
+            // Check and record direction
+            if( dir==0 ) {
+                dir = Math.abs(dir0);
+                Node rhs = parseShift();
+                lhs = makeCompBool(dir0,lhs.unkeep(),rhs); // Convert to a bool
+            } else if( dir == Math.abs(dir0) ) {
+                // e0 < lhs < ???
+                Node ifNode = new IfNode(ctrl(), lhs).peephole();
+                Node ifT = new CProjNode(ifNode.  keep(), 0, "True" ).peephole();
+                Node ifF = new CProjNode(ifNode.unkeep(), 1, "False").peephole();
+                // False side does nothing
+                ScopeNode fScope = _scope.dup();
+                fScope.ctrl(ifF);
+                // True side executes next part of range
+                ctrl(ifT);
+                _scope.addGuards(ifT,lhs,false);
+                Node rhs = parseShift();
+                _scope.removeGuards(ifT); // TODO: I think should remain true as long as possible
+                Node next = makeCompBool(dir0, lhs, rhs).keep();
+                // Merge result
+                RegionNode r = ctrl(_scope.mergeScopes(fScope, loc()));
+                assert next._type.meet(lhs._type).isa( TypeInteger.BOOL );
+                lhs = peep(new PhiNode("",TypeInteger.BOOL,r,next.unkeep(),lhs.unkeep()));
+                r.peephole();
+            } else {
+                throw error("Mixing relational directions in a chained relational test");
+            }
+        }
+        return lhs;
+    }
+
+    private Node makeCompBool( int dir0, Node lhs, Node rhs ) {
+        // Convert to a bool
+        if( Math.abs(dir0)==2 ) // Swap direction
+            { Node tmp = lhs; lhs = rhs; rhs = tmp; }
+        lhs = peep(dir0 < 0 ? new BoolNode.LE(lhs,rhs) : new BoolNode.LT(lhs,rhs));
+        return peep(lhs.widen());
+    }
+
+
+    /**
+     * Parse an additive expression
+     *
+     * <pre>
+     *     shiftExpr : additiveExpr (('<<' | '>>' | '>>>') additiveExpr)*
+     * </pre>
+     * @return a shift expression {@link Node}, never {@code null}
+     */
+    private Node parseShift() {
+        Node lhs = parseAddition();
+        while( true ) {
+            if( false ) ;
+            else if( match("<<") ) lhs = new ShlNode(loc(),lhs,null);
+            else if( match(">>>")) lhs = new ShrNode(loc(),lhs,null);
+            else if( match(">>") ) lhs = new SarNode(loc(),lhs,null);
+            else break;
+            lhs.setDef(2,parseAddition());
+            ParseException err;
+            if( (err=lhs.err()) != null )
+                throw err;
+            lhs = peep(lhs.widen());
+        }
+        return lhs;
+    }
+
+    /**
+     * Parse an additive expression
+     *
+     * <pre>
+     *     additiveExpr : multiplicativeExpr (('+' | '-') multiplicativeExpr)*
+     * </pre>
+     * @return an add expression {@link Node}, never {@code null}
+     */
+    private Node parseAddition() {
+        Node lhs = parseMultiplication();
+        while( true ) {
+            if( false ) ;
+            else if( match("+") ) lhs = new AddNode(lhs,null);
+            else if( match("-") ) lhs = new SubNode(lhs,null);
+            else break;
+            lhs.setDef(2,parseMultiplication());
+            lhs = peep(lhs.widen());
+        }
+        return lhs;
+    }
+
+    /**
+     * Parse an multiplicativeExpr expression
+     *
+     * <pre>
+     *     multiplicativeExpr : unaryExpr (('*' | '/') unaryExpr)*
+     * </pre>
+     * @return a multiply expression {@link Node}, never {@code null}
+     */
+    private Node parseMultiplication() {
+        var lhs = parseUnary();
+        while( true ) {
+            if( false ) ;
+            else if( match("*") ) lhs = new MulNode(lhs,null);
+            else if( match("/") ) lhs = new DivNode(lhs,null);
+            else break;
+            lhs.setDef(2,parseUnary());
+            lhs = peep(lhs.widen());
+        }
+        return lhs;
+    }
+
+    /**
+     * Parse a unary minus expression.
+     *
+     * <pre>
+     *     unaryExpr : ('-') unaryExpr | '!') unaryExpr | postfixExpr | primaryExpr | '--' Id | '++' Id
+     * </pre>
+     * @return a unary expression {@link Node}, never {@code null}
+     */
+    private Node parseUnary() {
+        // Pre-dec/pre-inc
+        int old = pos();
+        if( match("--") || match("++") ) {
+            int delta = _lexer.peek(-1)=='+' ? 1 : -1; // Pre vs post
+            String name = _lexer.matchId();
+            if( name!=null ) {
+                Var n = _scope.lookup(name);
+                if( n != null && !(n.type() instanceof TypeMemPtr) ) {
+                    if( n._final )
+                        throw error("Cannot reassign final '"+n._name+"'");
+                    Node expr = n.type() instanceof TypeFloat
+                        ?        peep(new AddFNode(_scope.in(n),con(TypeFloat.constant(delta))))
+                        : zsMask(peep(new  AddNode(_scope.in(n),con(delta))),n.type());
+                    _scope.update(n,expr);
+                    return expr;
+                }
+            }
+            // Reset, try again
+            pos(old);
+        }
+        if (match("-")) return peep(new MinusNode(parseUnary()).widen());
+        if (match("!")) return peep(new   NotNode(parseUnary()));
+        // Else be a primary expression
+        return parsePrimary();
+    }
+
+    /**
+     * Parse a primary expression:
+     *
+     * <pre>
+     *     primaryExpr : integerLiteral | "string" | 'char' | true | false | null |
+     *                   new Type | '(' expression ')' | Id['++','--'] |
+     *                   [static.]* Id
+     * </pre>
+     * @return a primary {@link Node}, never {@code null}
+     */
+    private Node parsePrimary() {
+        if( _lexer.isNumber(_lexer.peek()) ) return parseLiteral();
+        if( _lexer.peek('"') ) return newString(parseString());
+        if( matchx("true" ) ) return con(1);
+        if( matchx("false") ) return ZERO;
+        if( matchx("null" ) ) return NIL;
+        if( match ("'"    ) ) return parseChar();
+        if( match ("("    ) ) return parsePostfix(require(parseAsgn(), ")"));
+        if( matchx("new"  ) ) return parsePostfix(alloc());
+        if( match ("{"    ) ) return parsePostfix(require(func(),"}"));
+
+        // Parse static variable lookup: `type.fld` in the type namespace
+        // CNC: not a full type parse, just a typename parse
+        int pos = pos();
+        Type t = type();
+        if( t!=null ) {
+            if( peek('.') )
+                // A namespace lookup is not a reference declaration.
+                return parsePostfix(con(TYPES.get(((TypeMemPtr)t)._obj._name)));
+            //pos(pos); // TODO: not a `type.fld`
+            //return null;
+            throw Utils.TODO();
+        }
+
+        // Expect an identifier now
+
+        // - if null, make fref, normal var handling
+        // - if final constant, normal var handling
+        // - if method var, scan skipping blocks & methods, must hit correct struct no fcns
+        // - if normal var, scan skipping blocks, allowing last fcn
+        // - NO fcns nested in methods, NO methods nested in fcns
+
+        String id = _lexer.matchId();
+        if( id == null || KEYWORDS.contains(id) )
+            throw errorSyntax("an identifier or expression");
+        Var var = _scope.lookup(id);
+
+        if( var==null ) {
+            // If missing, assume a forward reference
+            _scope.define(id, FRefNode.FREF_TYPE, true, XCTRL, loc());
+            var = _scope.lookup(id);
+        }
+
+        // If a method var, allow nested blocks and methods, but not fcns or other structs.
+        // Else safety check for accessing fields out of function scope.
+        if( instance(var) ) {
+            Node self = _scope.in(_scope.lookup("self")); // Insert self reference
+            return parsePostfixName(self,id);
+        }
+
+        // Load local value
+        Node rvalue = _scope.in(var);
+        if( rvalue._type == Type.BOTTOM )
+            if( rvalue instanceof FRefNode )
+                return parsePostfix(rvalue);
+            else throw error("Cannot read uninitialized field '"+id+"'");
+
+        // Check for assign-update, x += e0;
+        char ch = _lexer.matchOperAssign();
+        if( ch==0  )            // Normal primary, check for postfix updates
+            return parsePostfix(rvalue);
+        // Assign-update direct into Scope
+        if( var._final )
+            throw error("Cannot reassign final '"+var._name+"'");
+        Node op = opAssign(ch,rvalue, var.type() );
+        _scope.update(var,op);
+        return postfix(ch) ? rvalue.unkeep() : op;
+    }
+
+    // true if instance variable lookup (var is in any number of nested blocks,
+    // then an instance function then inside a struct declaration).
+    private boolean instance(Var var ) {
+        // If a method var, allow nested blocks and methods, but not fcns or other structs
+        Kind kind = _scope.kind(var);
+        if( kind instanceof Kind.Define ) {
+            for( int i = _scope.depth()-1; i>=0 && var._idx < _scope._kinds.at(i)._lexSize; i-- ) {
+                Kind xkind = _scope._kinds.at(i);
+                if( xkind instanceof Kind.Block ) continue;
+                if( xkind instanceof Kind.Func ) {
+                    if( _scope._kinds.at(i-1)==kind )
+                        return true; // Instance variable: lookup in a method in a decl
+                }
+                throw Utils.TODO();
+            }
+        } else {
+            // If a normal var, allow any nested blocks, and a last fcn -
+            // but not functions further out (which involves capture).
+            Node def = _scope.in(var._idx);
+            for( int i = _scope.depth()-1; i>=0 && var._idx < _scope._kinds.at(i)._lexSize; i-- )
+                if( _scope._kinds.at(i) instanceof Kind.Func &&
+                    !(def instanceof FRefNode) && !(var._final && def._type.isConstant()) )
+                    throw error("Variable '"+var._name+"' is out of function scope and must be a final constant");
+        }
+        return false;
+    }
+
+    // Check for assign-update, "x += e0".
+    // Returns "x + e0"; the caller assigns value.
+    // if ch is postfix, then lhs is kept and caller will unkeep and return it.
+    private Node opAssign( char ch, Node lhs, Type t ) {
+        // RHS of the update.
+        lhs.keep();             // Alive across parseAsgn
+        Node rhs =
+            (byte)ch ==  1 ? con( 1) : // var++
+            (byte)ch == -1 ? con(-1) : // var--
+            parseAsgn();               // var op= rhs
+        if( !postfix(ch) ) lhs.unkeep();   // Allow to die in next peep
+        // 4 cases:
+        // int + int ==>> narrow int
+        // int + flt ==>> error, caller must fail assigning flt into int
+        // flt + int ==>> use float op, wrap toFloat()
+        // flt + flt ==>> use float op
+        Node op = switch(ch) {
+        case 1, (char)-1,
+             '+'        -> new AddNode(lhs,rhs);
+        case '-'        -> new SubNode(lhs,rhs);
+        case '*'        -> new MulNode(lhs,rhs);
+        case '/'        -> new DivNode(lhs,rhs);
+        case '&'        -> new AndNode(loc(),lhs,rhs);
+        case '|'        -> new  OrNode(loc(),lhs,rhs);
+        case '^'        -> new XorNode(loc(),lhs,rhs);
+        case Lexer.SHL  -> new ShlNode(loc(),lhs,rhs);
+        case Lexer.SAR  -> new SarNode(loc(),lhs,rhs);
+        case Lexer.SHR  -> new ShrNode(loc(),lhs,rhs);
+        default         -> throw Utils.TODO();
+        };
+        // Convert to float ops, or narrow int types; error if not declared type.
+        // Also, if postfix LHS is still keep()
+        return liftExpr(peep(op.widen()),t,true);
+    }
+
+
+    /**
+       Parse an allocation
+     */
+    private Node alloc() {
+        Type t = type();
+        if( t==null ) throw error("Expected a type");
+        // Parse ary[ length_expr ]
+        if( match("[") ) {
+            if( !t.makeZero().isa(t) )
+                throw error("Cannot allocate a non-nullable, since arrays always zero/null fill");
+            Node len = parseAsgn();
+            if( !(len._type instanceof TypeInteger) )
+                throw error("Cannot allocate an array with length "+len._type);
+            require("]");
+            TypeMemPtr tmp = typeAry(t,false);
+            return newArray(tmp._obj,len);
+        }
+
+        if( !(t instanceof TypeMemPtr tmp) )
+            throw error("Cannot allocate a "+t.str());
+
+        // Parse new struct { default_initialization }
+        StructNode s = INITS.get(tmp._obj._name);
+        if( s==null ) throw error("Unknown struct type '" + tmp._obj._name + "'");
+
+        Field[] fs = s._ts._fields;
+        // if the object is fully initialized, we can skip a block here.
+        // Check for constructor block:
+        boolean hasConstructor = match("{");
+        Ary<Node> init=s._inputs;  int idx=0;
+        if( hasConstructor ) {
+            idx = _scope.nIns();
+            // Push a scope, and pre-assign all struct fields.
+            _scope.push(new Kind.Block());
+            Lexer loc = loc();
+            for( int i=0; i<fs.length; i++ )
+                // An initial TOP means the field needs to be initialized.  We
+                // store a BOT initially; any partial init will fall to BOT
+                // (merge BOT and the partial) and be obviously only a partial
+                // init.  To be initialized the field needs a full clobber.
+                _scope.define(fs[i]._fname, fs[i]._t, fs[i]._final, s.in(i)._type==Type.TOP ? con(Type.BOTTOM) : s.in(i), loc);
+            // Parse the constructor body
+            require(parseBlock(new Kind.Alloc(tmp)),"}");
+            init = _scope._inputs;
+        }
+        // Check that all fields are initialized
+        for( int i=idx; i<init.size(); i++ )
+            if( init.at(i)._type == Type.TOP || init.at(i)._type == Type.BOTTOM )
+                throw error("'"+tmp._obj._name+"' is not fully initialized, field '" + fs[i-idx]._fname + "' needs to be set in a constructor");
+        Node ptr = newStruct(tmp._obj, off(tmp._obj, " len"), idx, init );
+        if( hasConstructor )
+            _scope.pop();
+        return ptr;
+    }
+
+
+    /**
+     * Return a NewNode initialized memory.
+     * @param obj is the declared type, with GLB fields
+     * @param init is a collection of initialized fields
+     */
+    private Node newStruct( TypeStruct obj, Node size, int idx, Ary<Node> init ) {
+        Field[] fs = obj._fields;
+        if( fs==null )
+            throw error("Unknown struct type '" + obj._name + "'");
+        Node prior = mem().keep();
+        MemMergeNode input = new MemMergeNode((Node)null);
+        for( Field f : fs ) if( !f._one ) input.alias(f._alias,prior);
+        // Allocation zeroes its fields; nonzero initializers become explicit Stores.
+        Node[] ns = new Node[3];
+        ns[0] = ctrl();
+        ns[1] = input.peephole();
+        ns[2] = size;
+        Node nnn = new NewNode(TypeMemPtr.make(obj),ns).peephole().keep();
+        Node ptr = new ProjNode(nnn,0,obj._name).peephole().keep();
+        Node out = new ProjNode(nnn,1,"$mem").peephole().keep();
+        MemMergeNode after = new MemMergeNode(prior);
+        for( Field f : fs ) if( !f._one ) after.alias(f._alias,out);
+        mem(after.peephole());
+        out.unkeep();
+        nnn.unkeep();
+        prior.unkill();
+        for( int i=0; i<fs.length; i++ ) {
+            Node val = init.get(idx+i);
+            if( !fs[i]._one && val._type != val._type.makeZero() ) {
+                Field f = fs[i];
+                Node st = new StoreNode(loc(),f._fname,f._alias,f._t,mem(),ptr,off(obj,f._fname),val,true).peephole();
+                mem(new MemMergeNode(mem(),f._alias,st).peephole());
+            }
+        }
+        return ptr.unkeep();
+    }
+
+    private static final Ary<Node> ALTMP = new Ary<>(Node.class);
+    private Node newArray(TypeStruct ary, Node len) {
+        ConFldOffNode base = off(ary, "[]");
+        int scale= ary.aryScale();
+        Node size = peep(new AddNode(base,peep(new ShlNode(null,len.keep(),con(scale)))));
+        ALTMP.clear();  ALTMP.add(len.unkeep()); ALTMP.add(con(ary._fields[1]._t.makeZero()));
+        return newStruct(ary,size,0,ALTMP);
+    }
+    private Node newString(String s) {
+        TypeMemPtr tmp = typeAry(TypeInteger.U8,true);
+        int  lenAlias = tmp._obj.field("#" )._alias;
+        int elemAlias = tmp._obj.field("[]")._alias;
+        TypeConAryB con = TypeConAryB.make(s);
+        Type elem = con.elem();
+        // Make a TMP, not-null (byte)2, singleton (true) (requires text
+        // strings are hash-interned), with a TypeStruct having a constant
+        // array body.
+        TypeMemPtr str = TypeMemPtr.make((byte)2,TypeStruct.makeAry("[]u8", TypeInteger.constant(s.length()), lenAlias, con, elemAlias, true),true);
+        assert str.isConstant();
+        return con(str.makeRO());
+    }
+
+    // Memory is one hidden SSA variable, including across branches and loops.
+    private Node mem() { return _scope.mem(); }
+    private void mem(Node n) { _scope.mem(n); }
+
+    private void store(String name, int alias, Type glb, Node ptr, Node off, Node val, boolean init, Node ctrl) {
+        if( !init && ptr._type instanceof TypeMemPtr view && view._ro && ctrl()._type!=Type.XCONTROL )
+            throw error("Cannot modify final field '"+name+"'");
+        Node prior = mem().keep();
+        Node st = new StoreNode(loc(),name,alias,glb,prior,ptr,off,val,init);
+        st.setDef(0,ctrl);
+        st = st.peephole();
+        mem(new MemMergeNode(prior,alias,st).peephole());
+        prior.unkill();
+    }
+
+    /**
+     * Parse postfix expression; this can be a field expression, an array
+     * lookup or a postfix operator like '#'
+     *
+     * <pre>
+     *     expr ('.' FIELD)* [ = expr ]       // Field reference
+     *     expr '#'                           // Postfix unary read operator
+     *     expr ['++' | '--' ]                // Postfix unary write operator
+     *     expr ('[' expr ']')* = [ = expr ]  // Array reference
+     *     expr '(' [args,]* ')'              // Function call
+     * </pre>
+     */
+    private Node parsePostfix(Node expr) {
+        String name;
+        if( match(".") )      name = requireId();
+        else if( match("#") ) name = "#";
+        else if( match("[") ) name = "[]";
+        else if( match("(") ) return parsePostfix(require(functionCall(expr,null),")"));
+        else return expr;       // No postfix
+
+        return parsePostfixName(expr,name);
+    }
+
+    /**
+     * Parse postfix expression; this can be a field expression, an array
+     * lookup or a postfix operator like '#'
+     *
+     * <pre>
+     *     expr ['++' | '--' ]                 // Postfix unary write operator
+     *     expr [ [op]= expr ]                 // Field reference
+     *     expr ('[' expr ']')* [ [op]= expr ] // Array reference
+     * </pre>
+     */
+    private Node parsePostfixName(Node expr, String name) {
+
+        if( expr._type==Type.NIL )
+            throw error("Accessing unknown field '" + name + "' from 'null'");
+
+        // Sanity check expr for being a reference
+        if( !(expr._type instanceof TypeMemPtr ptr) )
+            throw error( "Expected "+(name=="#" || name=="[]" ? "array" : "reference")+" but found " + expr._type.str() );
+
+        // Find the field from the Type.  Lookup in the base object field names.
+        TypeMemPtr ptr2 = (TypeMemPtr)TYPES.get(ptr._obj._name);
+        if( !ptr._obj.isAry() )
+            ptr = ptr.makeFrom((TypeStruct)ptr._obj.join(ptr2._obj)); // Resolve the shape, retaining access.
+        TypeStruct base = ptr._obj;
+        int fidx = base.find(name);
+        if( fidx == -1 )
+            throw error("Accessing unknown field '" + name + "' from '" + ptr.str() + "'");
+
+        // Get field type and layout offset from base type and field index fidx
+        Field f = base._fields[fidx];  // Field from field index
+        Type tf = f._t;
+        if( tf instanceof TypeMemPtr ftmp && ftmp.isFRef() )
+            tf = ftmp.makeFrom(((TypeMemPtr)(TYPES.get(ftmp._obj._name)))._obj);
+        if( base.isAry() && tf instanceof TypeConAry con )
+            tf = con.elem();
+
+        expr.keep();
+        // Field offset; fixed for structs, computed for arrays
+        Node off = (name.equals("[]")       // If field is an array body
+            // Array index math
+            ? peep(new AddNode(off(base,"[]"),peep(new ShlNode(null,require(parseAsgn(),"]"),con(base.aryScale())))))
+            // Struct field offsets are hardwired
+            : off(base,name)).keep();
+
+        // Disambiguate "obj.fld==x" boolean test from "obj.fld=x" field assignment
+        if( matchOpx('=','=') ) {
+            Node val = parseAsgn().keep();
+            Node lift = liftExpr( val, tf, false );
+
+            store(name,f._alias,tf,expr.unkeep(),off.unkeep(),lift,false,base.isAry() ? ctrl() : null);
+            return val.unkeep();        // "obj.a = expr" returns the expression while updating memory
+        }
+
+        // Load field
+        Node load = f._one && INITS.containsKey( base._name )
+            ? INITS.get(base._name).in(base.find(name))
+            : new LoadNode(loc(),name, f._alias, tf, mem(), expr, off);
+        // Arrays include control, as a proxy for a safety range check
+        // Structs don't need this; they only need a NPE check which is
+        // done via the type system.
+        if( base.isAry() && !name.equals("#") ) load.setDef(0,ctrl());
+        load = peep(load);
+
+        // Check for assign-update, "ptr.fld += expr" or "ary[idx]++"
+        char ch = _lexer.matchOperAssign();
+        if( ch!=0 ) {
+            Node op = opAssign(ch,load,tf);
+            store(name,f._alias,tf,expr.unkeep(),off.unkeep(),op,false,base.isAry() ? ctrl() : null);
+            load = postfix(ch) ? load.unkeep() : op;
+            // And use the original loaded value as the result
+            return load;
+            //throw Utils.TODO(); // NO POSTFIX AFTER STORE, JUST RETURN
+        } else {
+            off.unkill();
+            // Method call: Loaded a function from a named field, AND the base
+            // field type is final.
+            if( load._type instanceof TypeFunPtr && name!="[]" &&
+                !(load instanceof ExternNode) &&
+                ((TypeMemPtr)TYPES.get(base._name))._obj.field(name)._final &&
+                // And calling a function
+                match("(") ) {
+                return parsePostfix(require(functionCall(load,expr),")"));
+            }
+
+            // Drop expr, keeping load alive
+            load.keep();
+            expr.unkill();
+            load.unkeep();
+        }
+
+        return parsePostfix(load);
+    }
+
+
+    // zero/sign extend.  "i" is limited to either classic unsigned (min==0) or
+    // classic signed (min=minus-power-of-2); max=power-of-2-minus-1.
+    private Node zsMask(Node val, Type t ) {
+        if( val._type instanceof TypeFloat && t instanceof TypeInteger )
+            val = new ToIntegerNode(val).peephole();
+        if( !(val._type instanceof TypeInteger tval && t instanceof TypeInteger t0 && !tval.isa(t0)) ) {
+            if( !(val._type instanceof TypeFloat tval && t instanceof TypeFloat t0 && !tval.isa(t0)) )
+                return val;
+            // Float rounding
+            return peep(new RoundF32Node(val));
+        }
+        if( t0._min==0 )        // Unsigned
+            return peep(new AndNode(null,val,con(t0._max)));
+        // Signed extension
+        int shift = Long.numberOfLeadingZeros(t0._max)-1;
+        Node shf = con(shift);
+        if( shf._type==TypeInteger.ZERO )
+            return val;
+        return peep(new SarNode(null,peep(new ShlNode(null,val,shf.keep())),shf.unkeep()));
+    }
+
+    /**
+     * Parse a function body; the caller will parse the surrounding "{}"
+     *
+     * <pre>
+     *     { [type arg,]* -> expr }
+     *     { expr } // The no-argument function
+     * </pre>
+     */
+    private Node func() {
+        Ary<Type> ts = new Ary<>(Type.class);
+        Ary<String> ids = new Ary<>(String.class);
+        java.util.BitSet finals = new java.util.BitSet();
+
+        // Defined in constructor?  Add `self` argument.  "static" calls still
+        // add a `self` they just ignore it.
+        if( _scope._kinds.last() instanceof Kind.Define define ) {
+            // Upgrade defined struct to latest fields
+            TypeMemPtr tmp = (TypeMemPtr)TYPES.get(define._tmp._obj._name);
+            ts .push(tmp);
+            ids.push("self");
+        }
+
+        // Parse other arguments
+        _lexer.skipWhiteSpace();
+        Lexer loc = loc();      // First argument location
+        while( true ) {
+            Type t = type();    // Arg type
+            if( t==null ) break;
+            finals.set(ids.size(),bindingFinal(t));
+            String id = requireId();
+            ts .push(t );       // Push type/arg pairs
+            ids.push(id);
+            match(",");
+        }
+        require("->");
+        // Make a concrete function type, with a fidx
+        TypeFunPtr tfp = _code.makeFun(TypeFunPtr.make(false,false,ts.asAry(),Type.BOTTOM));
+        ReturnNode ret = parseFunctionBody(tfp,loc,finals,ids.asAry());
+        return new FunPtrNode(ret._fun.sig(),ret).peephole();
+    }
+
+    /**
+     *  Parse function call arguments; caller will parse the surrounding "()"
+     * <pre>
+     *   ( arg* )
+     * </pre>
+     */
+    private Node functionCall(Node fcn, Node self) {
+        if( fcn._type == Type.NIL )
+            throw error("Calling a null function pointer");
+        if( !(fcn instanceof FRefNode) && !fcn._type.isa(TypeFunPtr.BOT) )
+            throw error("Expected a function but got "+fcn._type.glb(false).str());
+        fcn.keep();            // Keep while parsing args
+
+        Ary<Node> args = new Ary<>( Node.class );
+        args.push(null);        // Space for ctrl,mem
+        args.push(null);
+        if( self != null )      // Method call has a self
+            args.push(self);
+        while( !peek(')') ) {
+            Node arg = parseAsgn();
+            if( arg==null ) break;
+            args.push(arg.keep());
+            if( !match(",") ) break;
+        }
+        // Control & memory after parsing args
+        args.set(0,ctrl().keep());
+        args.set(1,_scope.mem().keep());
+        args.push(fcn);        // Function pointer
+        // Unkeep them all
+        for( Node arg : args )
+            arg.unkeep();
+        // Dead into the call?  Skip all the node gen
+        if( ctrl()._type == Type.XCONTROL ) {
+            for( Node arg : args )
+                if( arg.isUnused() )
+                    arg.kill();
+            return con(Type.TOP);
+        }
+
+        // Into the call
+        CallNode call = (CallNode)new CallNode(loc(), args.asAry()).peephole();
+        // Post-call setup
+        CallEndNode cend = (CallEndNode)new CallEndNode(call).peephole();
+        call.peephole();        // Rerun peeps after CallEnd, allows early inlining
+        // Control from CallEnd
+        ctrl(new CProjNode(cend,0,ScopeNode.CTRL).peephole());
+        // A call may update any alias, so its memory result is the new whole state.
+        _scope.mem(new ProjNode(cend,1,ScopeNode.MEM0).peephole());
+        // Call result
+        return new ProjNode(cend,2,"#2").peephole();
+    }
+
+    // Just after parsing "type foo = " can parse `"C"`
+    private boolean isExternDecl( ) {
+        int old = pos();
+        String s = parseString();
+        if( "C".equals(s) ) return true;
+        pos(old);
+        return false;
+    }
+    // External linked constant
+    private Node externDecl( String ex, Type t ) {
+        if( t instanceof TypeFunPtr tfp ) // Generic TFP from type parse
+            t  = _code.makeFun(tfp);      // Get a FIDX, becomes a constant
+        return new ExternNode(t,ex).peephole();
+    }
+
+    /**
+     * Parse integer literal
+     *
+     * <pre>
+     *     integerLiteral: [1-9][0-9]* | [0]
+     *     floatLiteral: [digits].[digits]?[e [digits]]?
+     * </pre>
+     */
+    private ConstantNode parseLiteral() { return con(_lexer.parseNumber()); }
+    public static Node con( long con ) { return con==0 ? ZERO : con(TypeInteger.constant(con));  }
+    public static ConstantNode con( Type t ) { return (ConstantNode)new ConstantNode(t).peephole();  }
+    public static ConFldOffNode off( TypeStruct base, String fname ) { return (ConFldOffNode)(new ConFldOffNode(base._name,fname).peephole()); }
+    public Node peep( Node n ) {
+        // Peephole, then improve with lexically scoped guards
+        return _scope.upcastGuard(n.peephole());
+    }
+
+    // Parse a string or null
+    private String parseString() {
+        if( !peek('"') ) return null;
+        _lexer.inc();
+        StringBuilder sb = new StringBuilder();
+        while( !_lexer.isEOF() ) {
+            char c = _lexer.nextChar();
+            if( c=='"' ) return sb.toString();
+            if( c!='\\' ) {
+                sb.append(c);
+                continue;
+            }
+            if( _lexer.isEOF() )
+                throw error("Unclosed string");
+            sb.append(escapedChar("string"));
+        }
+        throw error("Unclosed string");
+    }
+
+    private char escapedChar(String kind) {
+        char esc = _lexer.nextChar();
+        return switch( esc ) {
+        case '0'  -> '\u0000';
+        case 'n'  -> '\n';
+        case 't'  -> '\t';
+        case 'r'  -> '\r';
+        case '\\' -> '\\';
+        case '"'  -> '"';
+        case '\'' -> '\'';
+        default -> throw error("Unknown "+kind+" escape \\\\"+esc);
+        };
+    }
+
+    // Already parsed "'"
+    private Node parseChar() {
+        if( _lexer.isEOF() ) throw error("Unclosed character");
+        char c = _lexer.nextChar();
+        if( c=='\\' ) {
+            if( _lexer.isEOF() ) throw error("Unclosed character");
+            c = escapedChar("character");
+        }
+        return require(con(TypeInteger.constant(c)),"'");
+    }
+
+    //////////////////////////////////
+    // Utilities for lexical analysis
+
+    // Return true and skip if "syntax" is next in the stream.
+    private boolean match (String syntax) { return _lexer.match (syntax); }
+    // Match must be "exact", not be followed by more id letters
+    private boolean matchx(String syntax) { return _lexer.matchx(syntax); }
+    private boolean matchOp(char c0 ) { return _lexer.matchOp(c0);  }
+    private boolean matchOpx(char c0, char c1) { return _lexer.matchOpx(c0,c1);  }
+    // Return true and do NOT skip if 'ch' is next
+    private boolean peek(char ch) { return _lexer.peek(ch); }
+    private boolean peekIsId() { return _lexer.peekIsId(); }
+
+    // ch is +/- 1, means oper++ or oper-- means postfix
+    private static boolean postfix(char ch) {
+        return (byte)ch== 1 || (byte)ch== -1;
+    }
+
+    public int pos() { return _lexer._position; }
+    private int pos(int pos) {
+        int old = _lexer._position;
+        _lexer._position = pos;
+        return old;
+    }
+    private Type posT(int pos) { _lexer._position = pos; return null; }
+    // Source code location
+    Lexer loc() { return new Lexer(_lexer); }
+
+
+    // Require and return an identifier
+    private String requireId() {
+        String id = _lexer.matchId();
+        if (id != null && !KEYWORDS.contains(id) ) return id.intern();
+        throw error("Expected an identifier, found '"+id+"'");
+    }
+
+    private String matchId() {
+        int old = pos();
+        String id = _lexer.matchId();
+        if( id==null ) return null;
+        if( !KEYWORDS.contains(id) ) return id;
+        pos(old);
+        return null;
+    }
+
+    // Require an exact match
+    private Parser require(String syntax) { require(null, syntax); return this; }
+    private <N> N require(N n, String syntax) {
+        if (match(syntax)) return n;
+        throw errorSyntax(syntax);
+    }
+
+    ////////////////////////////////////
+    // Lexer components
+
+    // Lexer provides low level access to the raw file bytes, peeks and matches
+    // short strings, parses numbers, skips comments and whitespace, tracks
+    // line numbers, allows the parse position to be saved and restored, and
+    // serves as a location indicator for errors.
+
+    public static class Lexer {
+
+        // Input buffer; an array of text bytes read from a file or a string
+        private final byte[] _input;
+        // Tracks current position in input buffer
+        private int _position = 0;
+
+        //
+        private int _line_number = 1;
+        // Start of current line
+        private int _line_start = 0;
+
+        /**
+         * Record the source text for lexing
+         */
+        public Lexer(String source) {
+            this(source.getBytes());
+        }
+
+        /**
+         * Direct from disk file source
+         */
+        public Lexer(byte[] buf) {
+            _input = buf;
+        }
+
+        /**
+         *  Copy a lexer from a lexer
+         */
+        private Lexer(Lexer l) {
+            _input = l._input;
+            _position = l._position;
+            _line_number = l._line_number;
+            _line_start = l._line_start;
+        }
+
+        // Very handy in the debugger, shows the unparsed program
+        @Override
+        public String toString() {
+            return new String(_input, _position, _input.length - _position);
+        }
+
+        // True if at EOF
+        private boolean isEOF() {
+            return _position >= _input.length;
+        }
+
+        // Peek next character, or report EOF
+        private char peek() {
+            return isEOF() ? Character.MAX_VALUE   // Special value that causes parsing to terminate
+                    : (char) _input[_position];
+        }
+        // Just crash if misused
+        public byte peek(int off) { return _input[_position+off]; }
+
+        private void inc() {
+            if( _position++ < _input.length && _input[_position-1] == '\n' ) {
+                _line_number++;
+                _line_start = _position;
+            }
+        }
+        // Does not honor LF, so caller must roll back position on a LF
+        private char nextChar() {
+            char ch = peek();
+            inc();
+            return ch;
+        }
+
+        // True if a white space
+        private boolean isWhiteSpace() {
+            return peek() <= ' '; // Includes all the use space, tab, newline, CR
+        }
+
+        /**
+         * Return the next non-white-space character
+         */
+        private void skipWhiteSpace() {
+            while( true ) {
+                if( isWhiteSpace() ) inc();
+                // Skip // to end of line
+                else if( _position+2 < _input.length &&
+                         _input[_position  ] == '/' &&
+                         _input[_position+1] == '/') {
+                    inc(); inc();
+                    while( !isEOF() && _input[_position] != '\n' )
+                        inc();
+                } else if( _position+2 < _input.length &&
+                         _input[_position  ] == '/' &&
+                         _input[_position+1] == '*') {
+                    // Skip /*comment*/
+                    while( !isEOF() && !(_input[_position-1] == '*' && _input[_position] == '/'))
+                        inc();
+                    inc();
+                } else break;
+            }
+        }
+
+        // Next non-white-space character, or EOF
+        public char nextXChar() { skipWhiteSpace(); return nextChar(); }
+
+        // Return true, if we find "syntax" after skipping white space; also
+        // then advance the cursor past syntax.
+        // Return false otherwise, and do not advance the cursor.
+        boolean match(String syntax) {
+            assert syntax.indexOf('\n')==-1; // No newlines in match
+            skipWhiteSpace();
+            int len = syntax.length();
+            if (_position + len > _input.length) return false;
+            for (int i = 0; i < len; i++)
+                if ((char) _input[_position + i] != syntax.charAt(i))
+                    return false;
+            _position += len;
+            return true;
+        }
+
+        // Match must be exact and not followed by more ID characters.
+        // Prevents identifier "ifxy" from matching an "if" statement.
+        boolean matchx(String syntax) {
+            if( !match(syntax) ) return false;
+            if( !isIdLetter(peek()) ) return true;
+            _position -= syntax.length();
+            return false;
+        }
+        // Match this char, and the next char must be different.
+        // Handles '&&' vs '&'
+        boolean matchOp( char c0 ) {
+            skipWhiteSpace();
+            if( _position+1 >= _input.length || _input[_position]!=c0 || _input[_position+1]==c0 )
+                return false;
+            inc();
+            return true;
+        }
+        // Match these two characters in a row
+        boolean matchOpx(char c0, char c1) {
+            skipWhiteSpace();
+            if( _position+1 >= _input.length || _input[_position]!=c0 || _input[_position+1]==c1 )
+                return false;
+            inc();
+            return true;
+        }
+
+        private boolean peek(char ch) {
+            skipWhiteSpace();
+            return peek()==ch;
+        }
+
+        boolean peekIsId() {
+            skipWhiteSpace();
+            return isIdStart(peek());
+        }
+
+        // Return an identifier or null
+        String matchId() {
+            return peekIsId() ? parseId() : null;
+        }
+
+        // Used for errors
+        String getAnyNextToken() {
+            if (isEOF()) return "";
+            if (isIdStart(peek())) return parseId();
+            if (isNumber(peek())) return parseNumberString();
+            if (isPunctuation(peek())) return parsePunctuation();
+            return String.valueOf(peek());
+        }
+
+
+        boolean isNumber(char ch) {return Character.isDigit(ch);}
+
+        // Return a constant Type, either TypeInteger or TypeFloat
+        private Type parseNumber() {
+            int old = _position;
+            int len = isLongOrDouble();
+            if( len > 0 ) {
+                if( len > 1 && _input[old]=='0' )
+                    throw error("Syntax error: integer values cannot start with '0'",this);
+                long i = Long.parseLong(new String(_input,old,len));
+                return TypeInteger.constant(i);
+            }
+            return TypeFloat.constant(Double.parseDouble(new String(_input,old,-len)));
+        }
+        private String parseNumberString() {
+            int old = _position;
+            int len = Math.abs(isLongOrDouble());
+            return new String(_input,old,len);
+        }
+
+        // Return +len that ends a long
+        // Return -len that ends a double
+        private int isLongOrDouble() {
+            int old = _position;
+            char c;
+            while( Character.isDigit(c=nextChar()) ) ;
+            if( !(c=='e' || c=='.') )
+                return --_position - old;
+            if( peek() == '-' ) nextChar();
+            while( Character.isDigit(c=nextChar()) || c=='e' || c=='.' ) ;
+            return -(--_position - old);
+        }
+
+        // First letter of an identifier
+        private boolean isIdStart(char ch) {
+            return Character.isAlphabetic(ch) || ch == '_';
+        }
+
+        // All characters of an identifier, e.g. "_x123"
+        private boolean isIdLetter(char ch) {
+            return Character.isLetterOrDigit(ch) || ch == '_';
+        }
+
+        private String parseId() {
+            int start = _position;
+            while (isIdLetter(nextChar())) ;
+            return new String(_input, start, --_position - start);
+        }
+
+        //
+        private boolean isPunctuation(char ch) {
+            return "=;[]<>()+-/*&|^".indexOf(ch) != -1;
+        }
+
+        private String parsePunctuation() {
+            int start = _position;
+            return new String(_input, start, 1);
+        }
+
+        // Next oper= character, or 0.
+        // As a convenience, mark "++" as a char 1 and "--" as char -1 (65535)
+        // Distinct tags for the multi-character compound operators.
+        static final char SHL = 2, SAR = 3, SHR = 4;
+
+        public char matchOperAssign() {
+            skipWhiteSpace();
+            if( match("<<=" ) ) return SHL;
+            if( match(">>>=") ) return SHR;
+            if( match(">>=" ) ) return SAR;
+            if( _position+2 >= _input.length ) return 0;
+            char ch0 = (char)_input[_position];
+            if( "+-/*&|^".indexOf(ch0) == -1 ) return 0;
+            char ch1 = (char)_input[_position+1];
+            if(               ch1 == '=' ) { _position += 2; return ch0; }
+            if( isIdLetter((char)_input[_position+2]) ) return 0;
+            if( ch0 == '+' && ch1 == '+' ) { _position += 2; return (char) 1; }
+            if( ch0 == '-' && ch1 == '-' ) { _position += 2; return (char)-1; }
+            return 0;
+        }
+    }
+
+    ParseException errorSyntax(String syntax) { return _errorSyntax("expected "+syntax);  }
+    private ParseException _errorSyntax(String msg) {
+        return error("Syntax error, "+msg+": " + _lexer.getAnyNextToken());
+    }
+    ParseException error(String msg) { return error(msg,_lexer); }
+    public static ParseException error(String msg, Lexer loc) { return new ParseException(msg,loc); }
+
+    public static class ParseException extends RuntimeException {
+        public final Lexer _loc;
+        // file:line:charoff err
+        //String msg = "src:"+_line_number+":"+(_position-_line_start)+" "+errorMessage;
+        ParseException( String msg, Lexer loc ) { super(msg);  _loc = loc; }
+    }
+
+}