[pushed] coroutines: Avoid functions with unlowered coroutine trees [PR95087].

[Iain Sandoe]

Hi,

Diagnosing bad uses of 'return' in coroutines is somewhat
tricky, since the user can use the keyword before we know
that the function is a coroutine (where such returns are not
permitted).  At present, we are just doing a check for any
use of 'return' and erroring on that.  However, we can't then
pass the function body on, since it will contain unlowered
coroutine trees.

This avoids the issue by dropping the entire function body
under that circumstance.  We could do better (for 11) but
this is intended to allow back-port of other fixes to 10.

tested on x86_64-darwin, linux / powerpc64-linux
pushed to master as obvious,
thanks
Iain

gcc/cp/ChangeLog:

        PR c++/95087
        * coroutines.cc (morph_fn_to_coro): If we see an
        early fatal error, drop the erroneous function body.

gcc/testsuite/ChangeLog:

        PR c++/95087
        * g++.dg/coroutines/co-return-syntax-08-bad-return.C:
        Adjust the testcase to do the compile (rather than an
        -fsyntax-only parse).
---
 gcc/cp/coroutines.cc                                           | 3 +++
 .../g++.dg/coroutines/co-return-syntax-08-bad-return.C         | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc
index f3cf242b4f1..0abc579e0cb 100644
--- a/gcc/cp/coroutines.cc
+++ b/gcc/cp/coroutines.cc
@@ -3585,6 +3585,9 @@ morph_fn_to_coro (tree orig, tree *resumer, tree 
*destroyer)
         ramp return value, since the user cannot fix this - a 'return' is
         not allowed in a coroutine.  */
       TREE_NO_WARNING (orig) = true;
+      /* Discard the body, we can't process it further.  */
+      pop_stmt_list (DECL_SAVED_TREE (orig));
+      DECL_SAVED_TREE (orig) = push_stmt_list ();
       return false;
     }
 
diff --git a/gcc/testsuite/g++.dg/coroutines/co-return-syntax-08-bad-return.C 
b/gcc/testsuite/g++.dg/coroutines/co-return-syntax-08-bad-return.C
index 4bfa41cd4a9..9b537548791 100644
--- a/gcc/testsuite/g++.dg/coroutines/co-return-syntax-08-bad-return.C
+++ b/gcc/testsuite/g++.dg/coroutines/co-return-syntax-08-bad-return.C
@@ -1,4 +1,4 @@
-//  { dg-additional-options "-fsyntax-only -w" }
+//  { dg-additional-options "-w" }
 
 #include "coro.h"
 
-- 
2.24.1