[Sema] Corrected the warn-on-throw-from-noexcept behavior to include nothrow

[erichkeane]

Summary

Discovered that 'nothrow' (which is supposed to be an alias for noexcept)
was not warning with a throw inside of it. This patch corrects the behavior
previously created to add 'nothrow' to this list.

[aaron.ballman]

Aside from a minor testing nit, LGTM! Thanks!

test/SemaCXX/warn-throw-out-noexcept-func.cpp

20

Can you also add a test for __declspec(nothrow)?

lib/Sema/AnalysisBasedWarnings.cpp

if (BodyCFG->getExit().pred_empty())
     return;
   SourceLocation OpLoc;
   if (hasThrowOutNonThrowingFunc(OpLoc, BodyCFG))
     EmitDiagForCXXThrowInNonThrowingFunc(S, OpLoc, FD);
 }
 
 static bool isNoexcept(const FunctionDecl *FD) {
   const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
-  if (FPT->isNothrow(FD->getASTContext()))
+  if (FPT->isNothrow(FD->getASTContext()) || FD->hasAttr<NoThrowAttr>())
     return true;
   return false;
 }
 
 //===----------------------------------------------------------------------===//
 // Check for missing return value.
 //===----------------------------------------------------------------------===//
 

test/SemaCXX/warn-throw-out-noexcept-func.cpp

 // RUN: %clang_cc1 %s  -fdelayed-template-parsing -fcxx-exceptions -fsyntax-only -Wexceptions -verify -std=c++11
 struct A_ShouldDiag {
   ~A_ShouldDiag(); // implicitly noexcept(true)
 };
 A_ShouldDiag::~A_ShouldDiag() { // expected-note {{destructor has a implicit non-throwing exception specification}}
   throw 1; // expected-warning {{has a non-throwing exception specification but can still throw}}
 }
 struct B_ShouldDiag {
   int i;
   ~B_ShouldDiag() noexcept(true) {} //no disg, no throw stmt
 };
 struct R_ShouldDiag : A_ShouldDiag {
   B_ShouldDiag b;
   ~R_ShouldDiag() { // expected-note  {{destructor has a implicit non-throwing exception specification}}
     throw 1; // expected-warning {{has a non-throwing exception specification but}}
   }
+  __attribute__((nothrow)) R_ShouldDiag() {// expected-note {{function declared non-throwing here}}
+    throw 1;// expected-warning {{has a non-throwing exception specification but}}
+  }
+  void __attribute__((nothrow)) SomeThrow() {// expected-note {{function declared non-throwing here}}
+   throw 1; // expected-warning {{has a non-throwing exception specification but}}
+  }
 };
 
 struct M_ShouldNotDiag {
   B_ShouldDiag b;
   ~M_ShouldNotDiag() noexcept(false);
 };
 
 M_ShouldNotDiag::~M_ShouldNotDiag() noexcept(false) {