2 files changed, 18 insertions, 3 deletions
diff --git a/chapter17/src/main/java/com/seaofnodes/simple/Parser.java b/chapter17/src/main/java/com/seaofnodes/simple/Parser.java
index abd70f89..fac012a4 100644
--- a/chapter17/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter17/src/main/java/com/seaofnodes/simple/Parser.java
@@ -141,6 +141,8 @@ public class Parser {
             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
         }};
     }
 
@@ -422,6 +424,8 @@ public class Parser {
                 ? Type.TOP
                 // Else takes the default
                 : t.makeInit();
+            // "var" and "val" require an expression to infer
+            if( init == null ) throw errorSyntax("expression");
             expr = con(init);
 
         } else if( !match("=") ) {     // Something else
@@ -453,6 +457,9 @@ public class Parser {
         Type e = expr._type;
         if( e instanceof TypeMemPtr tmp && tmp._obj._fields==null )
             e = TYPES.get(tmp._obj._name);
+        // "var" and "val" use TOP and BOTTOM - but just take the expression type.
+        if( t==Type.TOP || t==Type.BOTTOM )
+            t = expr._type.glb();
         // Type is sane
         if( !e.isa(t) )
             throw error("Type " + e.str() + " is not of declared type " + t.str());
@@ -468,7 +475,9 @@ public class Parser {
     /** Parse final: [!]asgn
      */
     private Node parseFinal(Type t) {
-        boolean xfinal = t!=null && match("!");
+        // TOP is a "val" marker - uses type inference for a "value", i.e. a final.
+        // BOT is a "var" marker - uses type inference for a "variable", i.e. not final
+        boolean xfinal = t==Type.TOP || (t!=null && match("!"));
         return parseAsgn(t,xfinal);
     }
 
@@ -761,8 +770,11 @@ public class Parser {
         // Expect an identifier now
         ScopeMinNode.Var n = requireLookupId("an identifier or expression");
         Node rvalue = _scope.in(n).keep();
-        if( matchx("++") || matchx("--") )
+        if( matchx("++") || matchx("--") ) {
+            if( n._final )
+                throw error("Cannot reassign final '"+n._name+"'");
             _scope.update(n,new AddNode(rvalue,con( _lexer.peek(-1)=='+' ? 1 : -1)).peephole());
+        }
         return rvalue.unkeep();
     }
 
diff --git a/chapter17/src/main/java/com/seaofnodes/simple/node/MinusNode.java b/chapter17/src/main/java/com/seaofnodes/simple/node/MinusNode.java
index 8a2c9406..760a4274 100644
--- a/chapter17/src/main/java/com/seaofnodes/simple/node/MinusNode.java
+++ b/chapter17/src/main/java/com/seaofnodes/simple/node/MinusNode.java
@@ -2,6 +2,7 @@ package com.seaofnodes.simple.node;
 
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
+import com.seaofnodes.simple.Utils;
 
 import java.util.BitSet;
 
@@ -22,7 +23,9 @@ public class MinusNode extends Node {
     public Type compute() {
         if( in(1)._type instanceof TypeInteger i0 ) {
             if( i0.isHigh() ) return TypeInteger.TOP;
-            return i0==TypeInteger.BOT ? TypeInteger.BOT : TypeInteger.make(-i0._max,-i0._min);
+            if( i0==TypeInteger.BOT || i0._min == Long.MIN_VALUE || i0._max == Long.MIN_VALUE )
+                return TypeInteger.BOT;
+            return TypeInteger.make(-i0._max,-i0._min);
         }
         return TypeInteger.TOP.meet(in(1)._type);
     }