[clang] [clang/AST] Make it possible to use SwiftAttr in type context (PR #108631)

[Gábor Horváth via cfe-commits]

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@@ -7147,6 +7147,60 @@ static bool HandleWebAssemblyFuncrefAttr(TypeProcessingState &State,
   return false;
 }
 
+static void HandleSwiftAttr(TypeProcessingState &State, TypeAttrLocation TAL,
+                            QualType &QT, ParsedAttr &PAttr) {
+  if (TAL == TAL_DeclName)
+    return;
+
+  Sema &S = State.getSema();
+  auto &D = State.getDeclarator();
+
+  // If the attribute appears in declaration specifiers
+  // it should be handled as a declaration attribute,
+  // unless it's associated with a type or a function
+  // prototype (i.e. appears on a parameter or result type).
+  if (State.isProcessingDeclSpec()) {
+    if (!(D.isPrototypeContext() ||
+          D.getContext() == DeclaratorContext::TypeName))
+      return;
+
+    if (auto *chunk = D.getInnermostNonParenChunk()) {
+      moveAttrFromListToList(PAttr, State.getCurrentAttributes(),
+                             const_cast<DeclaratorChunk *>(chunk)->getAttrs());
+      return;
+    }
+  }
+
+  StringRef Str;
+  if (!S.checkStringLiteralArgumentAttr(PAttr, 0, Str)) {
+    PAttr.setInvalid();
+    return;
+  }
+
+  // If the attribute as attached to a paren move it closer to
+  // the declarator. This can happen in block declarations when
+  // an attribute is placed before `^` i.e. `(__attribute__((...)) ^)`.
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Xazax-hun wrote:

I don't see a test case covering this scenario, should we add one?

https://github.com/llvm/llvm-project/pull/108631