[flang-commits] [flang] [Flang][Semantics] Fix crash on invalid function result declaration (PR #194648)

[via flang-commits]

https://github.com/ShashwathiNavada updated https://github.com/llvm/llvm-project/pull/194648

>From 82e6af002c9a3aa58c8d527e62969573e44a4267 Mon Sep 17 00:00:00 2001
From: ShashwathiNavada <shashwathinavada at gmail.com>
Date: Tue, 28 Apr 2026 09:41:39 -0500
Subject: [PATCH 1/2] Fix crash on invalid function result declaration; report
 semantic error instead

---
 flang/lib/Semantics/resolve-names.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index b6907cc792d76..409a793534399 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -496,6 +496,7 @@ class FuncResultStack {
     // Result symbol
     Symbol *resultSymbol{nullptr};
     bool inFunctionStmt{false}; // true between Pre/Post of FunctionStmt
+    bool completingType{false}; // re-entrancy guard for CompleteFunctionResultType
     // Functions with previous implicitly-typed references get those types
     // checked against their later definitions.
     const DeclTypeSpec *previousImplicitType{nullptr};
@@ -2874,6 +2875,7 @@ void FuncResultStack::CompleteFunctionResultType() {
   if (info && &info->scope == &scopeHandler_.currScope() &&
       info->resultSymbol) {
     if (info->parsedType) {
+      auto completingTypeScope{common::ScopedSet(info->completingType, true)};
       scopeHandler_.messageHandler().set_currStmtSource(info->source);
       if (const auto *type{
               scopeHandler_.ProcessTypeSpec(*info->parsedType, true)}) {
@@ -2908,7 +2910,15 @@ void FuncResultStack::CompleteFunctionResultType() {
 void FuncResultStack::CompleteTypeIfFunctionResult(Symbol &symbol) {
   if (FuncInfo * info{Top()}) {
     if (info->resultSymbol == &symbol) {
-      CompleteFunctionResultType();
+      if (info->completingType) {
+        if (!scopeHandler_.context().HasError(symbol)) {
+          scopeHandler_.SayAlreadyDeclared(symbol.name(),
+              info->resultName ? info->resultName->source : symbol.name());
+          scopeHandler_.context().SetError(symbol);
+        }
+      } else {
+        CompleteFunctionResultType();
+      }
     }
   }
 }

>From e4e1d09b267312701abf39ec3e90882abd0ab8c5 Mon Sep 17 00:00:00 2001
From: ShashwathiNavada <shashwathinavada at gmail.com>
Date: Tue, 28 Apr 2026 09:58:52 -0500
Subject: [PATCH 2/2] Simple change

---
 flang/lib/Semantics/resolve-names.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 409a793534399..17037f84e732e 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -496,7 +496,8 @@ class FuncResultStack {
     // Result symbol
     Symbol *resultSymbol{nullptr};
     bool inFunctionStmt{false}; // true between Pre/Post of FunctionStmt
-    bool completingType{false}; // re-entrancy guard for CompleteFunctionResultType
+    bool completingType{
+        false}; // re-entrancy guard for CompleteFunctionResultType
     // Functions with previous implicitly-typed references get those types
     // checked against their later definitions.
     const DeclTypeSpec *previousImplicitType{nullptr};