release/21.x: [clang][ObjC] Fix incorrect return type inference for discarded blocks (#154109)

[llvmbot]

Backport ec4e6aa

Requested by: @ojhunt

[llvmbot]

@cor3ntin What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-clang

Author: None (llvmbot)

Changes

Backport ec4e6aa

Requested by: @ojhunt

---

Full diff: https://github.com/llvm/llvm-project/pull/154210.diff

2 Files Affected:

• (modified) clang/lib/Parse/ParseExpr.cpp (+2-1)
• (added) clang/test/SemaObjCXX/discarded-block-type-inference.mm (+15)

diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index bc238a9517a37..3515343202de1 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/SemaObjCXX/discarded-block-type-inference.mm b/clang/test/SemaObjCXX/discarded-block-type-inference.mm
new file mode 100644
index 0000000000000..8e2587724a7f6
--- /dev/null
+++ b/clang/test/SemaObjCXX/discarded-block-type-inference.mm
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -std=c++23 -fsyntax-only -fobjc-arc -fblocks %s
+
+void  block_receiver(int (^)() );
+
+int f1() {
+  if constexpr (0)
+    (block_receiver)(^{ return 2; });
+  return 1;
+}
+
+int f2() {
+  if constexpr (0)
+    return (^{ return 2; })();
+  return 1;
+}

[github-actions]

@ojhunt (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.