fix(translate): improve error handling for local variables edge cases

Author: tetsuo-cpp

lib/Translation/ForthToMLIR/ForthToMLIR.cpp

@@ -1028,6 +1028,11 @@ LogicalResult ForthParser::parseBody(Value &stack) {
         Value step = popOp.getValue();
         emitLoopEnd(loc, ctx, step, stack);
 
+        //=== { outside word definition ===
+      } else if (currentToken.text == "{") {
+        return emitError(
+            "local variables can only be declared inside a word definition");
+
         //=== Normal word ===
       } else {
         Value newStack = emitOperation(currentToken.text, stack, loc);
@@ -1098,7 +1103,9 @@ LogicalResult ForthParser::parseLocals(Value &stack) {
     consume();
   }
 
-  // Skip '--' and output names until '}'
+  // Skip '--' and output names until '}'. Per ANS Forth, output names are
+  // documentation-only and have no semantic effect; we intentionally ignore
+  // them.
   if (currentToken.kind == Token::Kind::Word && currentToken.text == "--") {
     consume(); // consume '--'
     while (currentToken.kind != Token::Kind::EndOfFile) {

test/Translation/Forth/local-variables-error-outside-word.forth

@@ -0,0 +1,4 @@
+\ RUN: %not %warpforth-translate --forth-to-mlir %s 2>&1 | %FileCheck %s
+\ CHECK: local variables can only be declared inside a word definition
+\! kernel main
+{ x y -- }

test/Translation/Forth/local-variables-error-param-conflict.forth

@@ -0,0 +1,6 @@
+\ RUN: %not %warpforth-translate --forth-to-mlir %s 2>&1 | %FileCheck %s
+\ CHECK: local variable name 'DATA' conflicts with parameter name
+\! kernel main
+\! param DATA i64[256]
+: BAD { data -- } data ;
+BAD

test/Translation/Forth/local-variables-error-shared-conflict.forth

@@ -0,0 +1,6 @@
+\ RUN: %not %warpforth-translate --forth-to-mlir %s 2>&1 | %FileCheck %s
+\ CHECK: local variable name 'BUF' conflicts with shared memory name
+\! kernel main
+\! shared BUF i64[64]
+: BAD { buf -- } buf ;
+BAD