[clang] Fix spurious availability warning (PR #94377)

[Gábor Horváth via cfe-commits]

https://github.com/Xazax-hun created https://github.com/llvm/llvm-project/pull/94377

The availability attributes are stored on the function declarations. The code was looking for them in the function template declarations. This resulted in spuriously diagnosing availablity issues in contexts that are not available.

>From bc2b5844078fc95fb3b4e82eafd6e8392b22eab9 Mon Sep 17 00:00:00 2001
From: Gabor Horvath <gaborh at apple.com>
Date: Tue, 4 Jun 2024 17:29:23 +0100
Subject: [PATCH] Fix spurious availability warning

The availability attributes are stored on the function declarations.
The code was looking for them in the function template declarations.
This resulted in spuriously diagnosing availablity issues in contexts
that are not available.
---
 clang/include/clang/Sema/Initialization.h    |  2 +-
 clang/lib/Sema/SemaAvailability.cpp          |  5 +++++
 clang/test/Sema/attr-availability-macosx.cpp | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/Sema/attr-availability-macosx.cpp

diff --git a/clang/include/clang/Sema/Initialization.h b/clang/include/clang/Sema/Initialization.h
index 2072cd8d1c3ef..f443e327eaf32 100644
--- a/clang/include/clang/Sema/Initialization.h
+++ b/clang/include/clang/Sema/Initialization.h
@@ -212,7 +212,7 @@ class alignas(8) InitializedEntity {
     struct C Capture;
   };
 
-  InitializedEntity() {};
+  InitializedEntity() {}
 
   /// Create the initialization entity for a variable.
   InitializedEntity(VarDecl *Var, EntityKind EK = EK_Variable)
diff --git a/clang/lib/Sema/SemaAvailability.cpp b/clang/lib/Sema/SemaAvailability.cpp
index 330cd602297d4..3e5f90b450367 100644
--- a/clang/lib/Sema/SemaAvailability.cpp
+++ b/clang/lib/Sema/SemaAvailability.cpp
@@ -12,6 +12,7 @@
 
 #include "clang/AST/Attr.h"
 #include "clang/AST/Decl.h"
+#include "clang/AST/DeclTemplate.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Basic/DiagnosticSema.h"
 #include "clang/Basic/IdentifierTable.h"
@@ -46,6 +47,10 @@ static const AvailabilityAttr *getAttrForPlatform(ASTContext &Context,
   // Check each AvailabilityAttr to find the one for this platform.
   // For multiple attributes with the same platform try to find one for this
   // environment.
+  // The attribute is always on the FunctionDecl, not on the
+  // FunctionTemplateDecl.
+  if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(D))
+    D = FTD->getTemplatedDecl();
   for (const auto *A : D->attrs()) {
     if (const auto *Avail = dyn_cast<AvailabilityAttr>(A)) {
       // FIXME: this is copied from CheckAvailability. We should try to
diff --git a/clang/test/Sema/attr-availability-macosx.cpp b/clang/test/Sema/attr-availability-macosx.cpp
new file mode 100644
index 0000000000000..52f320d409281
--- /dev/null
+++ b/clang/test/Sema/attr-availability-macosx.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 "-triple" "arm64-apple-macosx10.15" -fsyntax-only -verify %s
+
+__attribute__((availability(macos,introduced=11)))
+inline bool try_acquire() {
+  return true;
+}
+
+template <class T>
+__attribute__((availability(macos,introduced=11)))
+bool try_acquire_for(T duration) { // expected-note{{'try_acquire_for<int>' has been marked as being introduced in macOS 11 here, but the deployment target is macOS 10.15}}
+  return try_acquire();
+}
+
+int main() {
+  try_acquire_for(1); // expected-warning{{'try_acquire_for<int>' is only available on macOS 11 or newer}}
+  // expected-note at -1{{enclose 'try_acquire_for<int>' in a __builtin_available check to silence this warning}}
+}
\ No newline at end of file