This bug comes from a missing check when a function declaration has a
late-specified return type and a constrained auto type specifier. By
adding such a check, we can catch such uses and diagnose them as errors.
Successfully bootstrapped and regretested on x86_64-pc-linux-gnu:
adds 6 new test results and 4 UNSUPPORTED results to g++.sum. The 4
UNSUPPORTED results are due to the fact that concepts are not supported
before c++20, so tests cannot pass with c++17 and lower standards.
PR c++/100589
gcc/cp/ChangeLog:
* decl.cc (grokdeclarator): Issue an error for a declarator with
constrained auto type specifier and trailing return types.
gcc/testsuite/ChangeLog:
* g++.dg/other/pr100589.C: New test.
Signed-off-by: Da Xie <xxie...@163.com>
---
gcc/cp/decl.cc | 7 +++++++
gcc/testsuite/g++.dg/other/pr100589.C | 7 +++++++
2 files changed, 14 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/other/pr100589.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 9ca8c6c4481..f283ed996a2 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -14037,6 +14037,13 @@ grokdeclarator (const cp_declarator *declarator,
"invalid use of %<decltype(auto)%>");
return error_mark_node;
}
+ else if (is_constrained_auto (type))
+ {
+ error_at (typespec_loc, "invalid use of "
+ "constrained auto type specifier "
+ "in function with trailing return type");
+ return error_mark_node;
+ }
tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
if (!tmpl)
if (tree late_auto = type_uses_auto (late_return_type))
diff --git a/gcc/testsuite/g++.dg/other/pr100589.C
b/gcc/testsuite/g++.dg/other/pr100589.C
new file mode 100644
index 00000000000..3fa054ed34d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/other/pr100589.C
@@ -0,0 +1,7 @@
+// PR c++/100589
+// { dg-do compile { target c++20 } }
+
+template<class T>
+concept false_concept = false;
+
+false_concept auto f() -> int; // { dg-error "constrained auto type
specifier.* trailing return type" }
\ No newline at end of file
--
2.34.1
