[Parser] Do not involve IRBuilder for imported functions (#6286)

We previously had a bug where we would begin and end an IRBuilder context for
imported functions even though they don't have bodies. For functions that return
results, ending this empty scope should have produced an error except that we
had another bug where we only produced that error for multivalue functions. We
did not previously have imported multivalue functions in wat-kitchen-sink.wast,
so both of these bugs went undetected. Fix both bugs and update the test to
include an imported multivalue function so that it would have failed without
this fix.

5 files changed, 16 insertions, 15 deletions

diff --git a/src/parser/context-defs.cpp b/src/parser/context-defs.cpp
index e5c598b6b..2d4d305ed 100644
--- a/src/parser/context-defs.cpp
+++ b/src/parser/context-defs.cpp
@@ -50,16 +50,6 @@ ParseDefsCtx::makeTypeUse(Index pos,
   return it->second;
 }
 
-Result<> ParseDefsCtx::addFunc(Name,
-                               const std::vector<Name>&,
-                               ImportNames*,
-                               TypeUseT,
-                               std::optional<LocalsT>,
-                               Index pos) {
-  CHECK_ERR(withLoc(pos, irBuilder.visitEnd()));
-  return Ok{};
-}
-
 Result<> ParseDefsCtx::addGlobal(Name,
                                  const std::vector<Name>&,
                                  ImportNames*,
diff --git a/src/parser/contexts.h b/src/parser/contexts.h
index c14a555c5..5dd48bc59 100644
--- a/src/parser/contexts.h
+++ b/src/parser/contexts.h
@@ -1324,12 +1324,15 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
                                std::optional<HeapTypeT> type,
                                ParamsT* params,
                                ResultsT* results);
+
   Result<> addFunc(Name,
                    const std::vector<Name>&,
                    ImportNames*,
                    TypeUseT,
                    std::optional<LocalsT>,
-                   Index pos);
+                   Index) {
+    return Ok{};
+  }
 
   Result<>
   addTable(Name, const std::vector<Name>&, ImportNames*, TableTypeT, Index) {
diff --git a/src/parser/wat-parser.cpp b/src/parser/wat-parser.cpp
index f247dbf48..50a47d7b6 100644
--- a/src/parser/wat-parser.cpp
+++ b/src/parser/wat-parser.cpp
@@ -177,7 +177,10 @@ Result<> parseModule(Module& wasm, std::string_view input) {
 
     for (Index i = 0; i < decls.funcDefs.size(); ++i) {
       ctx.index = i;
-      CHECK_ERR(ctx.visitFunctionStart(wasm.functions[i].get()));
+      auto* f = wasm.functions[i].get();
+      if (!f->imported()) {
+        CHECK_ERR(ctx.visitFunctionStart(f));
+      }
       WithPosition with(ctx, decls.funcDefs[i].pos);
       if (auto parsed = func(ctx)) {
         CHECK_ERR(parsed);
@@ -186,6 +189,9 @@ Result<> parseModule(Module& wasm, std::string_view input) {
         assert(im);
         CHECK_ERR(im);
       }
+      if (!f->imported()) {
+        CHECK_ERR(ctx.irBuilder.visitEnd());
+      }
     }
 
     // Parse exports.
diff --git a/src/wasm/wasm-ir-builder.cpp b/src/wasm/wasm-ir-builder.cpp
index 8098856e4..bf3c38c1e 100644
--- a/src/wasm/wasm-ir-builder.cpp
+++ b/src/wasm/wasm-ir-builder.cpp
@@ -162,7 +162,6 @@ Result<Expression*> IRBuilder::pop(size_t size) {
   // Find the suffix of expressions that do not produce values.
   auto hoisted = hoistLastValue();
   CHECK_ERR(hoisted);
-
   if (!hoisted) {
     // There are no expressions that produce values.
     if (scope.unreachable) {
@@ -700,6 +699,9 @@ Result<Expression*> IRBuilder::finishScope(Block* block) {
     // the top.
     auto hoisted = hoistLastValue();
     CHECK_ERR(hoisted);
+    if (!hoisted) {
+      return Err{"popping from empty stack"};
+    }
   }
 
   Expression* ret = nullptr;
diff --git a/test/lit/wat-kitchen-sink.wast b/test/lit/wat-kitchen-sink.wast
index 32a70d913..7dea0d3c2 100644
--- a/test/lit/wat-kitchen-sink.wast
+++ b/test/lit/wat-kitchen-sink.wast
@@ -271,7 +271,7 @@
 
  ;; imported functions
  (func (export "f5.0") (export "f5.1") (import "mod" "f5"))
- (import "mod" "imported-f" (func (param) (result)))
+ (import "mod" "imported-f" (func (param) (result i32 i64)))
 
  ;; imported tags
  (tag $imported (export "t0.0") (export "t0.1") (import "mod" "t0") (param i32 i64))
@@ -283,7 +283,7 @@
 
  ;; CHECK:      (import "mod" "f5" (func $fimport$0 (type $void)))
 
- ;; CHECK:      (import "mod" "imported-f" (func $fimport$1 (type $void)))
+ ;; CHECK:      (import "mod" "imported-f" (func $fimport$1 (type $3) (result i32 i64)))
 
  ;; CHECK:      (import "mod" "t0" (tag $imported (param i32 i64)))