[Clang] [Sema] Effects: Correctly detect (x ? a : b) as nonblocking when a and b are (#111224)

Correctly detect `(x ? a : b)` as nonblocking when `a` and `b` are. Use 
`FunctionEffectsRef::get` to get to the actual effect set instead of trying 
to retrieve it manually via the `FunctionProtoType` as we may have to 
look through function pointers etc. in some cases.

---------

Co-authored-by: Doug Wyatt <[email protected]>

Author: dougsonos

clang/lib/Sema/SemaFunctionEffects.cpp

@@ -1048,15 +1048,14 @@ class Analyzer {
     }
 
     void checkIndirectCall(CallExpr *Call, QualType CalleeType) {
-      auto *FPT =
-          CalleeType->getAs<FunctionProtoType>(); // Null if FunctionType.
       FunctionEffectKindSet CalleeEffects;
-      if (FPT)
-        CalleeEffects.insert(FPT->getFunctionEffects());
+      if (FunctionEffectsRef Effects = FunctionEffectsRef::get(CalleeType);
+          !Effects.empty())
+        CalleeEffects.insert(Effects);
 
       auto Check1Effect = [&](FunctionEffect Effect, bool Inferring) {
-        if (FPT == nullptr || Effect.shouldDiagnoseFunctionCall(
-                                  /*direct=*/false, CalleeEffects))
+        if (Effect.shouldDiagnoseFunctionCall(
+                /*direct=*/false, CalleeEffects))
           addViolation(Inferring, Effect, ViolationID::CallsExprWithoutEffect,
                        Call->getBeginLoc());
       };

clang/test/Sema/attr-nonblocking-constraints.cpp

@@ -156,6 +156,17 @@ void nb10(
 	static_cast<void (*)()>(fp1)(); // expected-warning {{function with 'nonblocking' attribute must not call non-'nonblocking' expression}}
 }
 
+// Expression involving indirection
+int nb10a() [[clang::nonblocking]];
+int nb10b() [[clang::nonblocking]];
+int blocking();
+
+int nb10c(bool x) [[clang::nonblocking]]
+{
+	int y = (x ? nb10a : blocking)(); // expected-warning {{attribute 'nonblocking' should not be added via type conversion}}
+	return (x ? nb10a : nb10b)(); // No diagnostic.
+}
+
 // Interactions with nonblocking(false)
 void nb11_no_inference_1() [[clang::nonblocking(false)]] // expected-note {{function does not permit inference of 'nonblocking'}}
 {