[Heavy] Fix valuerefs in error handling

Author: ricejasonf

heavy/lib/OpGen.cpp

@@ -143,7 +143,7 @@ mlir::Value OpGen::GetSingleResult(heavy::Value V) {
   mlir::Value Result = Visit(V);
 
   // Take the first continuation arg.
-  if (isa<HeavyValueRefsTy>(Result.getType()))
+  if (Result && isa<HeavyValueRefsTy>(Result.getType()))
     Result = create<LoadRefOp>(heavy::SourceLocation(), Result, /*Index*/0);
 
   if (CheckError())
@@ -533,12 +533,6 @@ void OpGen::PopContinuationScope() {
 
 bool OpGen::isLocalDefineAllowed() {
   return IsLocalDefineAllowed;
-#if 0
-  mlir::Block* Block = Builder.getInsertionBlock();
-  if (!Block) return false;
-  return (Block->empty() ||
-          isa<BindingOp>(Block->back()));
-#endif
 }
 
 // createSyntaxSpec

heavy/test/Evaluate/define-syntax.scm

@@ -3,7 +3,27 @@
 
 ;; TODO Local let-syntax needs to be tested/supported.
 
+(define-syntax capture-late-bind
+  (syntax-rules ()
+    ((capture-late-bind x)
+     ((lambda ()
+       (define storage 0)
+       (lambda ()
+         (set! storage
+           (if (symbol? ok)
+               ok 'oknotyet))
+         (write storage)))))))
+
+; CHECK: oknotyet
+((capture-late-bind 5))
+(newline)
+
 (define ok 'ok!)
+
+; CHECK-NEXT: ok
+((capture-late-bind 5))
+
+(newline)
 (define-syntax my-lambda
   (syntax-rules (=>)
     ((my-lambda formals => body)

heavy/test/Evaluate/lambda.scm

@@ -78,3 +78,16 @@
     msg)))
 (write global)
 (newline)
+
+; Test capture of lazy global binding.
+(define (fnzzz)
+  (define temp lazy-binding-fn)
+  (lambda (x)
+    (temp x)))
+
+(define (lazy-binding-fn x)
+  (write x)
+  (newline))
+
+; CHECK: just-lazy
+((fnzzz) 'just-lazy)