[coroutines] Improved diagnostics when unhandled_exception is missing…

… in the promise_type

Summary: Now we helpfully provide a note pointing at the promise_type in question.

Reviewers: EricWF, GorNishanov

Reviewed By: GorNishanov

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D33481

llvm-svn: 303752

clang/lib/Sema/SemaCoroutine.cpp

@@ -120,8 +120,7 @@ static QualType lookupPromiseType(Sema &S, const FunctionProtoType *FnType,
   return PromiseType;
 }
 
-/// Look up the std::coroutine_traits<...>::promise_type for the given
-/// function type.
+/// Look up the std::experimental::coroutine_handle<PromiseType>.
 static QualType lookupCoroutineHandleType(Sema &S, QualType PromiseType,
                                           SourceLocation Loc) {
   if (PromiseType.isNull())
@@ -729,8 +728,7 @@ void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
   }
 
   if (isa<CoroutineBodyStmt>(Body)) {
-    // FIXME(EricWF): Nothing todo. the body is already a transformed coroutine
-    // body statement.
+    // Nothing todo. the body is already a transformed coroutine body statement.
     return;
   }
 
@@ -1030,6 +1028,8 @@ bool CoroutineStmtBuilder::makeOnException() {
             : diag::
                   warn_coroutine_promise_unhandled_exception_required_with_exceptions;
     S.Diag(Loc, DiagID) << PromiseRecordDecl;
+    S.Diag(PromiseRecordDecl->getLocation(), diag::note_defined_here)
+        << PromiseRecordDecl;
     return !RequireUnhandledException;
   }
 

clang/test/SemaCXX/coroutine-unhandled_exception-warning.cpp

@@ -16,7 +16,11 @@
 using std::experimental::suspend_always;
 using std::experimental::suspend_never;
 
+#ifndef DISABLE_WARNING
+struct promise_void { // expected-note {{defined here}}
+#else
 struct promise_void {
+#endif
   void get_return_object();
   suspend_always initial_suspend();
   suspend_always final_suspend();

clang/test/SemaCXX/coroutines.cpp

@@ -540,7 +540,7 @@ coro<T> bad_implicit_return_dependent(T) { // expected-error {{'bad_promise_6' d
 }
 template coro<bad_promise_6> bad_implicit_return_dependent(bad_promise_6); // expected-note {{in instantiation}}
 
-struct bad_promise_7 {
+struct bad_promise_7 { // expected-note 2 {{defined here}}
   coro<bad_promise_7> get_return_object();
   suspend_always initial_suspend();
   suspend_always final_suspend();