[clang] [clang][ThreadSafety] Warn when constructor is trylock (PR #95290)

[Dan McArdle via cfe-commits]

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@@ -614,9 +619,23 @@ static bool checkTryLockFunAttrCommon(Sema &S, Decl *D, const ParsedAttr &AL,
     return false;
   }
 
-  // check that all arguments are lockable objects
+  // Check that all remaining arguments are lockable objects.
   checkAttrArgsAreCapabilityObjs(S, D, AL, Args, 1);
 
+  // Check that the attribute is applied to a function.
+  if (!D->isFunctionOrFunctionTemplate()) {
+    return false;
+  }
+  // Check that the function returns a boolean, integer, or pointer.
+  QualType ReturnType = D->getAsFunction()->getReturnType();
+  if (!ReturnType->isBooleanType() && !ReturnType->isIntegerType() &&
+      !ReturnType->isPointerType()) {
+    S.Diag(AL.getLoc(), diag::err_attribute_wrong_decl_type)
+        << AL << AL.isRegularKeywordAttribute()
+        << ExpectedFunctionReturningBoolIntegerOrPointer;
+    return false;
+  }
+
   return true;
 }
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dmcardle wrote:

I'm adding a some new logic for checking the success argument type. If I leave this as is, they will have the same style. If you feel strongly, I'm happy to apply DeMorgan's law here :) 

https://github.com/llvm/llvm-project/pull/95290