[14 PATCH] c++: Partially revert "Support lambdas attached to more places in modules" [PR118245]

[Nathaniel Shead]

Bootstrapped and regtested (just modules.exp and dg.exp=lambda*) on
x86_64-pc-linux-gnu, OK for 14 if full regtest succeeds?

-- >8 --

r14-9232-g3685fae23bb008 broke the ABI for lambdas in base classes,
causing ICEs when different lambdas got given the same mangled name.

This patch reverts the parser.cc changes from that patch to restore the
old behaviour.  The properly fixed behaviour is available in GCC 15.1
with r15-7202-g8990070b4297b9, but that change was not suitable for
backporting.

        PR c++/118245

gcc/cp/ChangeLog:

        * parser.cc (cp_parser_class_head): Remove lambda scope when
        parsing base classes.

gcc/testsuite/ChangeLog:

        * g++.dg/modules/lambda-7_a.H: Expect the test to fail.
        * g++.dg/modules/lambda-7_b.C: Likewise.
        * g++.dg/modules/lambda-7_c.C: Likewise.
        * g++.dg/cpp2a/lambda-uneval23.C: New test.

Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
---
 gcc/cp/parser.cc                             | 10 ++--------
 gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C |  7 +++++++
 gcc/testsuite/g++.dg/modules/lambda-7_a.H    |  2 +-
 gcc/testsuite/g++.dg/modules/lambda-7_b.C    |  1 +
 gcc/testsuite/g++.dg/modules/lambda-7_c.C    |  1 +
 5 files changed, 12 insertions(+), 9 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 0281d7eb99b..ed31fc6bfd5 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -27729,16 +27729,10 @@ cp_parser_class_head (cp_parser* parser,
   if (cp_lexer_next_token_is (parser->lexer, CPP_COLON))
     {
       if (type)
-       {
-         pushclass (type);
-         start_lambda_scope (TYPE_NAME (type));
-       }
+       pushclass (type);
       bases = cp_parser_base_clause (parser);
       if (type)
-       {
-         finish_lambda_scope ();
-         popclass ();
-       }
+       popclass ();
     }
   else
     bases = NULL_TREE;
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C 
b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C
new file mode 100644
index 00000000000..fa009f53ff2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval23.C
@@ -0,0 +1,7 @@
+// PR c++/118245
+// { dg-do compile { target c++20 } }
+
+template<auto> struct Cask {};
+struct T1 : Cask<[]{}> {
+  Cask<[]{}> c{};
+};
diff --git a/gcc/testsuite/g++.dg/modules/lambda-7_a.H 
b/gcc/testsuite/g++.dg/modules/lambda-7_a.H
index 5197114f76c..842aedc5fd9 100644
--- a/gcc/testsuite/g++.dg/modules/lambda-7_a.H
+++ b/gcc/testsuite/g++.dg/modules/lambda-7_a.H
@@ -1,4 +1,4 @@
 // { dg-additional-options "-fmodule-header -Wno-subobject-linkage" }
-// { dg-module-cmi {} }
+// { dg-ice "see PR c++/118245" { c++20 } }
 
 #include "lambda-7.h"
diff --git a/gcc/testsuite/g++.dg/modules/lambda-7_b.C 
b/gcc/testsuite/g++.dg/modules/lambda-7_b.C
index 2d781e93067..cd4d0f3aa65 100644
--- a/gcc/testsuite/g++.dg/modules/lambda-7_b.C
+++ b/gcc/testsuite/g++.dg/modules/lambda-7_b.C
@@ -1,4 +1,5 @@
 // { dg-additional-options "-fmodules-ts -fno-module-lazy 
-Wno-subobject-linkage" }
+// { dg-xfail-if "see PR c++/118245" { c++20 } }
 // Test for ODR deduplication
 
 #include "lambda-7.h"
diff --git a/gcc/testsuite/g++.dg/modules/lambda-7_c.C 
b/gcc/testsuite/g++.dg/modules/lambda-7_c.C
index f283681fa96..a3135a287ca 100644
--- a/gcc/testsuite/g++.dg/modules/lambda-7_c.C
+++ b/gcc/testsuite/g++.dg/modules/lambda-7_c.C
@@ -1,5 +1,6 @@
 // { dg-module-do run }
 // { dg-additional-options "-fmodules-ts -fno-module-lazy 
-Wno-subobject-linkage" }
+// { dg-xfail-if "see PR c++/118245" { c++20 } }
 
 import "lambda-7_a.H";
 
-- 
2.47.0