Fix bugs using keywords as ids

Add an exact 'matchx' for keywords.  Add a list of keywords.

int true=0; return true; // Expected id, found 'true'
int else=arg; if(else) else=2; else else=1; return else; // Expected id, found 'else'
inta=1; return a;  // undefined inta

3 files changed, 71 insertions, 19 deletions

diff --git a/chapter05/src/main/java/com/seaofnodes/simple/Parser.java b/chapter05/src/main/java/com/seaofnodes/simple/Parser.java
index a23f8d70..7ea74306 100644
--- a/chapter05/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter05/src/main/java/com/seaofnodes/simple/Parser.java
@@ -49,6 +49,19 @@ public class Parser {
     public ScopeNode _scope;
 
     /**
+     * List of keywords disallowed as identifiers
+     */
+    private final HashSet<String> KEYWORDS = new HashSet<>(){{
+            add("else");
+            add("false");
+            add("if");
+            add("return");
+            add("then");
+            add("true");
+        }};
+
+    
+    /**
      * 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
      */
@@ -116,11 +129,11 @@ public class Parser {
      * </pre>
      */
     private Node parseStatement() {
-        if (match("return")  ) return parseReturn();
-        else if (match("int")) return parseDecl();
-        else if (match("{"  )) return parseBlock();
-        else if (match("if" )) return parseIf();
-        else if (match("#showGraph")) return showGraph();
+        if (matchx("return")  ) return parseReturn();
+        else if (matchx("int")) return parseDecl();
+        else if (match ("{"  )) return parseBlock();
+        else if (matchx("if" )) return parseIf();
+        else if (matchx("#showGraph")) return showGraph();
         else return parseExpressionStatement();
     }
 
@@ -147,7 +160,7 @@ public class Parser {
         // Parse the false side
         _scope = fScope;        // Restore scope, then parse else block if any
         ctrl(ifF);              // Ctrl token is now set to ifFalse projection
-        if (match("else")) parseStatement();
+        if (matchx("else")) parseStatement();
 
         if( tScope.nIns() != ndefs || fScope.nIns() != ndefs )
             throw error("Cannot define a new name on one arm of an if");
@@ -286,13 +299,13 @@ public class Parser {
     private Node parsePrimary() {
         if( _lexer.isNumber() ) return parseIntegerLiteral();
         if( match("(") ) return require(parseExpression(), ")");
-        if( match("true" ) ) return new ConstantNode(TypeInteger.constant(1)).peephole();
-        if( match("false") ) return new ConstantNode(TypeInteger.constant(0)).peephole();
-        String name = requireId();
-        Node id = _scope.lookup(name);
-        if( id==null )
-            throw error("Undefined name '" + name + "'");
-        return id;
+        if( matchx("true" ) ) return new ConstantNode(TypeInteger.constant(1)).peephole();
+        if( matchx("false") ) return new ConstantNode(TypeInteger.constant(0)).peephole();
+        String name = _lexer.matchId();
+        if( name == null) return null;
+        Node n = _scope.lookup(name);
+        if( n!=null ) return n;
+        throw error("Undefined name '" + name + "'");
     }
 
     /**
@@ -310,13 +323,15 @@ public class Parser {
     // Utilities for lexical analysis
 
     // Return true and skip if "syntax" is next in the stream.
-    private boolean match(String syntax) { return _lexer.match(syntax); }
+    private boolean match (String syntax) { return _lexer.match (syntax); }
+    // Match must not be followed by more id letters
+    private boolean matchx(String syntax) { return _lexer.matchx(syntax); }
 
     // Require and return an identifier
     private String requireId() {
         String id = _lexer.matchId();
-        if (id != null) return id;
-        throw error("identifier");
+        if (id != null && !KEYWORDS.contains(id) ) return id;
+        throw error("Expected an identifier, found '"+id+"'");
     }
 
     // Require an exact match
@@ -402,11 +417,19 @@ public class Parser {
             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;
+                if ((char) _input[_position + i] != syntax.charAt(i))
+                    return false;
             _position += len;
             return true;
         }
 
+        boolean matchx(String syntax) {
+            if( !match(syntax) ) return false;
+            if( !isIdLetter(peek()) ) return true;
+            _position -= syntax.length();
+            return false;
+        }
+
         // Return an identifier or null
         String matchId() {
             skipWhiteSpace();
diff --git a/chapter05/src/main/java/com/seaofnodes/simple/type/TypeInteger.java b/chapter05/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
index e23840e0..f75a6788 100644
--- a/chapter05/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
+++ b/chapter05/src/main/java/com/seaofnodes/simple/type/TypeInteger.java
@@ -25,7 +25,7 @@ public class TypeInteger extends Type {
 
     @Override
     public String toString() {
-      return _print(new StringBuilder()).toString();
+        return _print(new StringBuilder()).toString();
     }
 
     @Override 
diff --git a/chapter05/src/test/java/com/seaofnodes/simple/Chapter05Test.java b/chapter05/src/test/java/com/seaofnodes/simple/Chapter05Test.java
index 8f09620e..32ac5aac 100644
--- a/chapter05/src/test/java/com/seaofnodes/simple/Chapter05Test.java
+++ b/chapter05/src/test/java/com/seaofnodes/simple/Chapter05Test.java
@@ -95,6 +95,26 @@ return c;
       StopNode stop = new Parser("return true;").parse();
       assertEquals("return 1;",stop.toString());
     }
+    
+    @Test
+    public void testChapter5Keyword1() {
+        try { 
+            new Parser("int true=0; return true;").parse();
+            fail();
+        } catch( RuntimeException e ) {
+            assertEquals("Expected an identifier, found 'true'",e.getMessage());
+        }
+    }
+      
+    @Test
+    public void testChapter5Keyword2() {
+        try { 
+            new Parser("int else=arg; if(else) else=2; else else=1; return else;").parse();
+            fail();
+        } catch( RuntimeException e ) {
+            assertEquals("Expected an identifier, found 'else'",e.getMessage());
+        }
+    }
       
     @Test
     public void testChapter4Peephole() {
@@ -197,6 +217,16 @@ return c;
     }
 
     @Test
+    public void testChapter4Bug3() {
+        try { 
+            new Parser("inta=1; return a;").parse();
+            fail();
+        } catch( RuntimeException e ) {
+            assertEquals("Undefined name 'inta'",e.getMessage());
+        }
+    }
+    
+    @Test
     public void testVarDecl() {
         Parser parser = new Parser("int a=1; return a;");
         StopNode ret = parser.parse();
@@ -242,7 +272,6 @@ return c;
         }
     }
 
-
     @Test
     public void testChapter2ParseGrammar() {
         Node._disablePeephole = true; // disable peephole so we can observe full graph