[PATCH] D30772: [coroutines] Fix assertion in DependentCoawaitExpr when the argument is non-dependent.

[Eric Fiselier via Phabricator via cfe-commits]

EricWF created this revision.
Herald added a subscriber: mehdi_amini.

A `co_await arg` expression has a dependent type whenever the promise type is still dependent, even if the argument to co_await is not. This is because we cannot attempt the `await_transform(<arg>)` until after we know the promise type.

This patch fixes an assertion in the constructor of `DependentCoawaitExpr` that asserted that `arg` must also be dependent.


https://reviews.llvm.org/D30772

Files:
  include/clang/AST/ExprCXX.h
  test/SemaCXX/coroutines.cpp


Index: test/SemaCXX/coroutines.cpp
===================================================================
--- test/SemaCXX/coroutines.cpp
+++ test/SemaCXX/coroutines.cpp
@@ -151,6 +151,12 @@
   co_return 42;
 }
 
+template <class T>
+void co_await_non_dependent_arg(T) {
+  co_await a;
+}
+template void co_await_non_dependent_arg(int);
+
 void mixed_yield() {
   co_yield 0; // expected-note {{use of 'co_yield'}}
   return; // expected-error {{not allowed in coroutine}}
Index: include/clang/AST/ExprCXX.h
===================================================================
--- include/clang/AST/ExprCXX.h
+++ include/clang/AST/ExprCXX.h
@@ -4236,7 +4236,9 @@
              /*InstantiationDependent*/ true,
              Op->containsUnexpandedParameterPack()),
         KeywordLoc(KeywordLoc) {
-    assert(Op->isTypeDependent() && Ty->isDependentType() &&
+    // NOTE: A co_await expression is dependent on the coroutines promise
+    // type and may be dependent even when the `Op` expression is not.
+    assert(Ty->isDependentType() &&
            "wrong constructor for non-dependent co_await/co_yield expression");
     SubExprs[0] = Op;
     SubExprs[1] = OpCoawait;


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