A return statement in a discarded statement is not used for return type
deduction, but we still want to do deduction for a return statement in a
lambda in a discarded statement.
Tested x86_64-pc-linux-gnu, applying to trunk.
PR c++/93442
* parser.c (cp_parser_lambda_expression): Clear in_discarded_stmt.
---
gcc/cp/parser.c | 6 ++++++
.../g++.dg/cpp1z/constexpr-if-lambda1.C | 16 ++++++++++++++++
2 files changed, 22 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda1.C
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 72037ee7b46..b8327823777 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -10530,6 +10530,10 @@ cp_parser_lambda_expression (cp_parser* parser)
parser->implicit_template_scope = 0;
parser->auto_is_implicit_function_template_parm_p = false;
+ /* The body of a lambda in a discarded statement is not discarded. */
+ bool discarded = in_discarded_stmt;
+ in_discarded_stmt = 0;
+
/* By virtue of defining a local class, a lambda expression has access to
the private variables of enclosing classes. */
@@ -10560,6 +10564,8 @@ cp_parser_lambda_expression (cp_parser* parser)
finish_struct (type, /*attributes=*/NULL_TREE);
+ in_discarded_stmt = discarded;
+
parser->num_template_parameter_lists = saved_num_template_parameter_lists;
parser->in_statement = in_statement;
parser->in_switch_statement_p = in_switch_statement_p;
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda1.C
b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda1.C
new file mode 100644
index 00000000000..64c4cd27fe6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda1.C
@@ -0,0 +1,16 @@
+// PR c++/93442
+// { dg-do compile { target c++17 } }
+
+struct bar {
+ int foo(){return 0;}
+};
+
+int foobar() {
+ if constexpr(true) {
+ return 0;
+ } else {
+ return [](){
+ return bar{};
+ }().foo();
+ }
+}
base-commit: 5aebfb71763c7c8d0bb96adcd0a5f94de96a2a13
--
2.18.1
