[pushed] c++: *this capture in const member fn [PR95193].

[Jason Merrill via Gcc-patches]

Here, the capture proxy for *this is const, but its DECL_VALUE_EXPR is not.
Don't ICE on this; it's a reasonable difference, since in C++ an rvalue of
scalar type does not have cv-qualifiers.

Tested x86_64-pc-linux-gnu, applying to trunk.

gcc/cp/ChangeLog:

        PR c++/95193
        * pt.c (tsubst_decl): Relax assert.

gcc/testsuite/ChangeLog:

        PR c++/95193
        * g++.dg/cpp1z/lambda-this7.C: New test.
---
 gcc/cp/pt.c                               |  3 ++-
 gcc/testsuite/g++.dg/cpp1z/lambda-this7.C | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/lambda-this7.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 907ca879c73..9c03c5a5bbd 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14633,7 +14633,8 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
                         && DECL_BIT_FIELD_TYPE (TREE_OPERAND (ve, 1)) == type)
                  type = TREE_TYPE (ve);
                else
-                 gcc_checking_assert (TREE_TYPE (ve) == type);
+                 gcc_checking_assert (TYPE_MAIN_VARIANT (TREE_TYPE (ve))
+                                      == TYPE_MAIN_VARIANT (type));
                SET_DECL_VALUE_EXPR (r, ve);
              }
            if (CP_DECL_THREAD_LOCAL_P (r)
diff --git a/gcc/testsuite/g++.dg/cpp1z/lambda-this7.C 
b/gcc/testsuite/g++.dg/cpp1z/lambda-this7.C
new file mode 100644
index 00000000000..8137061e161
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/lambda-this7.C
@@ -0,0 +1,11 @@
+// PR c++/95193
+// { dg-do compile { target c++17 } }
+
+struct X {
+  void foo() const {
+    auto GL1 = [*this](auto a) {
+    };
+
+    GL1("abc");
+  }
+};

base-commit: 4013baf99c38f7bca06a51f8301e8fb195ccfa33
-- 
2.18.1