[coroutines] Fix invalid source range in co_await call expressions.

[EricWF]

Summary

Currently an invalid source range is generated for the member call expressions of co_await. The end location of the call expression is the co_await token loc, while the start is the location of the operand. This causes crashes when the source range is used to produce diagnostics.

This patch fixes the issues by using the expression location instead of the token location when building the member calls.

[vsk]

Thanks, LGTM.

[modocache]

Excellent, thank you! I think this might fix PR34982?

lib/Sema/SemaCoroutine.cpp

if (E->getType()->isDependentType()) {
     return Res;
   }
 
   // If the expression is a temporary, materialize it as an lvalue so that we
   // can use it multiple times.
   if (E->getValueKind() == VK_RValue)
     E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
 
+  // The location of the `co_await` token cannot be used when constructing
+  // the member call expressions since it's before the location of `Expr`, which
+  // is used as the start of the member call expression.
+  SourceLocation CallLoc = E->getExprLoc();
+
   // Build the await_ready, await_suspend, await_resume calls.
   ReadySuspendResumeResult RSS =
-      buildCoawaitCalls(*this, Coroutine->CoroutinePromise, Loc, E);
+      buildCoawaitCalls(*this, Coroutine->CoroutinePromise, CallLoc, E);
   if (RSS.IsInvalid)
     return ExprError();
 
   Expr *Res =
       new (Context) CoawaitExpr(Loc, E, RSS.Results[0], RSS.Results[1],
                                 RSS.Results[2], RSS.OpaqueValue, IsImplicit);
 
   return Res;

test/SemaCXX/coroutine-source-location-crash.cpp

+// RUN: %clang_cc1 -triple x86_64-apple-darwin9 %s -std=c++14 -fcoroutines-ts \
+// RUN:    -fsyntax-only -ast-dump | FileCheck %s
+#include "Inputs/std-coroutine.h"
+
+using namespace std::experimental;
+
+struct A {
+  bool await_ready();
+  void await_resume();
+  template <typename F>
+  void await_suspend(F);
+};
+
+struct coro_t {
+  struct promise_type {
+    coro_t get_return_object();
+    suspend_never initial_suspend();
+    suspend_never final_suspend();
+    void return_void();
+    static void unhandled_exception();
+  };
+};
+
+// {{0x[0-9a-fA-F]+}} <line:[[@LINE+1]]:1, col:36>
+// CHECK-LABEL: FunctionDecl {{.*}} f 'coro_t (int)'
+coro_t f(int n) {
+  A a{};
+  // CHECK: CoawaitExpr {{0x[0-9a-fA-F]+}} <col:3, col:12>
+  // CHECK-NEXT: DeclRefExpr {{0x[0-9a-fA-F]+}} <col:12>
+  // CHECK-NEXT: CXXMemberCallExpr {{0x[0-9a-fA-F]+}} <col:12>
+  // CHECK-NEXT: MemberExpr {{0x[0-9a-fA-F]+}} <col:12>
+  co_await a;
+}