[gcc/devel/c++-coroutines] c++: Fix DMI with lambda 'this' capture [PR94205]

[gcc/devel/c++-coroutines] c++: Fix DMI with lambda 'this' capture [PR94205]

[Iain D Sandoe]

https://gcc.gnu.org/g:76f09260b7eccd6c3cfa3dcf3c22897fe12a8065

commit 76f09260b7eccd6c3cfa3dcf3c22897fe12a8065
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Mar 31 17:34:47 2020 -0400

    c++: Fix DMI with lambda 'this' capture [PR94205]
    
    We represent 'this' in a default member initializer with a PLACEHOLDER_EXPR.
    Normally in constexpr evaluation when we encounter one it refers to
    ctx->ctor, but when we're creating a temporary of class type, that replaces
    ctx->ctor, so a PLACEHOLDER_EXPR that refers to the type of the member being
    initialized needs to be replaced before that happens.
    
    gcc/cp/ChangeLog
    2020-03-31  Jason Merrill  <jason@redhat.com>
    
            PR c++/94205
            * constexpr.c (cxx_eval_constant_expression) [TARGET_EXPR]: Call
            replace_placeholders.
            * typeck2.c (store_init_value): Fix arguments to
            fold_non_dependent_expr.

Diff:
---
 gcc/cp/ChangeLog                              |  8 ++++++++
 gcc/cp/constexpr.c                            |  6 ++++++
 gcc/cp/tree.c                                 |  2 +-
 gcc/cp/typeck2.c                              |  2 +-
 gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi2.C | 20 ++++++++++++++++++++
 gcc/testsuite/g++.dg/cpp1z/lambda-this4.C     | 13 +++++++++++++
 6 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2814a866f5d..3b522e8278c 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2020-03-31  Jason Merrill  <jason@redhat.com>
+
+	PR c++/94205
+	* constexpr.c (cxx_eval_constant_expression) [TARGET_EXPR]: Call
+	replace_placeholders.
+	* typeck2.c (store_init_value): Fix arguments to
+	fold_non_dependent_expr.
+
 2020-03-31  Jason Merrill  <jason@redhat.com>
 
 	* constexpr.c (cxx_eval_constant_expression) [TARGET_EXPR]: Use
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index e85b3c113f0..91f0c3ba269 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -5553,6 +5553,12 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
 	tree init = TARGET_EXPR_INITIAL (t);
 	if ((AGGREGATE_TYPE_P (type) || VECTOR_TYPE_P (type)))
 	  {
+	    if (ctx->object)
+	      /* If the initializer contains any PLACEHOLDER_EXPR, we need to
+		 resolve them before we create a new CONSTRUCTOR for the
+		 temporary.  */
+	      init = replace_placeholders (init, ctx->object);
+
 	    /* We're being expanded without an explicit target, so start
 	       initializing a new object; expansion with an explicit target
 	       strips the TARGET_EXPR before we get here.  */
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index a2172dea0d8..5eb0dcd717a 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -3239,7 +3239,7 @@ replace_placeholders_r (tree* t, int* walk_subtrees, void* data_)
    a PLACEHOLDER_EXPR has been encountered.  */
 
 tree
-replace_placeholders (tree exp, tree obj, bool *seen_p)
+replace_placeholders (tree exp, tree obj, bool *seen_p /*= NULL*/)
 {
   /* This is only relevant for C++14.  */
   if (cxx_dialect < cxx14)
diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index bff4ddbcf81..cf1cb5ace66 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -871,7 +871,7 @@ store_init_value (tree decl, tree init, vec<tree, va_gc>** cleanups, int flags)
     {
       bool const_init;
       tree oldval = value;
-      value = fold_non_dependent_expr (value);
+      value = fold_non_dependent_expr (value, tf_warning_or_error, true, decl);
       if (DECL_DECLARED_CONSTEXPR_P (decl)
 	  || (DECL_IN_AGGR_P (decl)
 	      && DECL_INITIALIZED_IN_CLASS_P (decl)))
diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi2.C
new file mode 100644
index 00000000000..c51f734a134
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi2.C
@@ -0,0 +1,20 @@
+// PR c++/94205
+// { dg-do compile { target c++14 } }
+
+struct S
+{
+  struct A
+  {
+    S *p;
+    constexpr A(S* p): p(p) {}
+    constexpr operator int() { p->i = 5; return 6; }
+  };
+  int i;
+  int a = A(this);
+};
+
+
+constexpr S s = {};
+
+#define SA(X) static_assert((X),#X)
+SA(s.i == 5 && s.a == 6);
diff --git a/gcc/testsuite/g++.dg/cpp1z/lambda-this4.C b/gcc/testsuite/g++.dg/cpp1z/lambda-this4.C
new file mode 100644
index 00000000000..5d968791491
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/lambda-this4.C
@@ -0,0 +1,13 @@
+// PR c++/94205
+// { dg-do compile { target c++17 } }
+
+struct S
+{
+  int i;
+  int a = [this] { this->i = 5; return 6; } ();
+};
+
+
+constexpr S s = {};
+
+static_assert (s.i == 5 && s.a == 6);