https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98990
Bug ID: 98990
Summary: Internal compiler error when two overloaded functions
return `auto &&` and one accepts an `auto` parameter
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: david at doublewise dot net
Target Milestone: ---
The following valid translation unit
```
constexpr int x = 0;
constexpr auto && f() {
return x;
}
constexpr auto && f(auto) {
return x;
}
```
causes gcc to crash with
```
<source>:6:25: internal compiler error: same canonical type node for different
types 'auto&&' and 'auto&&'
6 | constexpr auto && f(auto) {
| ^
0x1ce6f09 internal_error(char const*, ...)
???:0
0x9c60ce comptypes(tree_node*, tree_node*, int)
???:0
0x78ef77 decls_match(tree_node*, tree_node*, bool)
???:0
0x7c003c cplus_decl_attributes(tree_node**, tree_node*, int)
???:0
0x79f277 grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
???:0
0x7a3916 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
???:0
0x8de23d c_parse_file()
???:0
0xa5b7c2 c_common_parse_file()
???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
```
See it live: https://godbolt.org/z/bnszYo
This code was accepted in gcc 10.2, but it is rejected by the upcoming 11.0.
