[clang][ObjC] Fix incorrect return type inference for discarded blocks

[ojhunt]

When parsing a block expression we were not entering a new eval context and as a result when parsing the block body we continue to treat any return statements as discarded so infer a void result.

This fixes the problem by introducing an evaluation context around the parsing of the body.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Oliver Hunt (ojhunt)

Changes

When parsing a block expression we were not entering a new eval context and as a result when parsing the block body we continue to treat any return statements as discarded so infer a void result.

This fixes the problem by introducing an evaluation context around the parsing of the body.

---

Full diff: https://github.com/llvm/llvm-project/pull/154109.diff

2 Files Affected:

• (modified) clang/lib/Parse/ParseExpr.cpp (+2-1)
• (modified) clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp (+10)

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index bc238a9517a37..d9e86405d338d 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -3342,7 +3342,8 @@ ExprResult Parser::ParseBlockLiteralExpression() {
     Actions.ActOnBlockError(CaretLoc, getCurScope());
     return ExprError();
   }
-
+ EnterExpressionEvaluationContextForFunction PotentiallyEvaluated(
+       Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
   StmtResult Stmt(ParseCompoundStatementBody());
   BlockScope.Exit();
   if (!Stmt.isInvalid())
diff --git a/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp b/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
index 05830de9891fe..4c3c23164908e 100644
--- a/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
+++ b/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -std=c++1z -verify %s
+// RUN: %clang_cc1 -std=c++1z -fblocks -verify %s -DBLOCK_TEST
 // RUN: %clang_cc1 -std=c++1z -verify %s -DUNDEFINED
 
 #ifdef UNDEFINED
@@ -254,6 +255,15 @@ namespace GH153884 {
     // expected-note@-1 {{in instantiation of function template specialization 'GH153884::f2()}}
     return false;
   }
+
+#if BLOCK_TEST
+void  block_receiver(int (^)() );
+int f3() {
+  if constexpr (0)
+    (block_receiver)(^{ return 2; });
+  return 1;
+}
+#endif
 }
 
 #endif

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff HEAD~1 HEAD --extensions cpp -- clang/lib/Parse/ParseExpr.cpp

View the diff from clang-format here.

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index 351534320..ca20093c7 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -3343,7 +3343,7 @@ ExprResult Parser::ParseBlockLiteralExpression() {
     return ExprError();
   }
   EnterExpressionEvaluationContextForFunction PotentiallyEvaluated(
-       Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
+      Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
   StmtResult Stmt(ParseCompoundStatementBody());
   BlockScope.Exit();
   if (!Stmt.isInvalid())

[cor3ntin]

LGTM once the bots are happy