[Bug c++/84611] New: internal compiler error: in operator[], at vec.h:826 (local_class_index())

["vegard.nossum at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84611

            Bug ID: 84611
           Summary: internal compiler error: in operator[], at vec.h:826
                    (local_class_index())
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vegard.nossum at gmail dot com
  Target Milestone: ---

Input:

template<typename = int>
struct a {
  a() {
    struct c;
    try {
    } catch (struct c {}) {
    }
  }
};

struct d {
  d();
  a<> b;
};

d::d() {};

Output:

xgcc -x c++ -c input.cc
input.cc: In constructor 'a< <template-parameter-1-1> >::a()':
input.cc:6:23: error: types may not be defined in exception-declarations
     } catch (struct c {}) {
                       ^
input.cc: In instantiation of 'a< <template-parameter-1-1> >::a() [with
<template-parameter-1-1> = int]':
input.cc:16:6:   required from here
input.cc:6:24: error: conflicting declaration 'struct a<
<template-parameter-1-1> >::a() [with <template-parameter-1-1> = int]::c'
     } catch (struct c {}) {
                        ^
input.cc:4:12: note: previous declaration as 'struct a<
<template-parameter-1-1> >::a() [with <template-parameter-1-1> = int]::c'
     struct c;
            ^
input.cc:6:7: internal compiler error: in operator[], at vec.h:826
     } catch (struct c {}) {
       ^~~~~
0xd70ab7 vec<tree_node*, va_gc, vl_embed>::operator[](unsigned int)
        /home/vegard/git/gcc/gcc/vec.h:826
0xd70ab7 local_class_index
        /home/vegard/git/gcc/gcc/cp/mangle.c:1921
0xd8e983 discriminator_for_local_entity
        /home/vegard/git/gcc/gcc/cp/mangle.c:1957
0xd8e983 write_local_name
        /home/vegard/git/gcc/gcc/cp/mangle.c:2058
0xd8e983 write_name
        /home/vegard/git/gcc/gcc/cp/mangle.c:964
0xd91dde write_class_enum_type
        /home/vegard/git/gcc/gcc/cp/mangle.c:2809
0xd91dde write_type
        /home/vegard/git/gcc/gcc/cp/mangle.c:2222
0xda3b3b mangle_special_for_type
        /home/vegard/git/gcc/gcc/cp/mangle.c:3955
0x120dfb7 get_tinfo_decl(tree_node*)
        /home/vegard/git/gcc/gcc/cp/rtti.c:446
0xcc859b eh_type_info(tree_node*)
        /home/vegard/git/gcc/gcc/cp/except.c:109
0xcc859b expand_start_catch_block(tree_node*)
        /home/vegard/git/gcc/gcc/cp/except.c:381
0x1261fb4 finish_handler_parms(tree_node*, tree_node*)
        /home/vegard/git/gcc/gcc/cp/semantics.c:1338
0x10bb6bf tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:16448
0x10b8bae tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:16426
0x10b7d64 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:16045
0x10ba0da tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:16322
0x10b7d64 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:16045
0x10ba0da tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:16322
0x10b051f instantiate_decl(tree_node*, bool, bool)
        /home/vegard/git/gcc/gcc/cp/pt.c:23386
0x11eeaf7 instantiate_pending_templates(int)
        /home/vegard/git/gcc/gcc/cp/pt.c:23502
Version:

xgcc (GCC) 8.0.1 20180204 (experimental)

built from git fdae6180ad24fa6303fa046114f3e4b66b8db34d

Seems to have been introduced since 7.3 because 7.3.0 on godbolt.org says:
<source>: In constructor 'a< <template-parameter-1-1> >::a()':
<source>:6:23: error: types may not be defined in exception-declarations
     } catch (struct c {}) {
                       ^
<source>: In instantiation of 'a< <template-parameter-1-1> >::a() [with
<template-parameter-1-1> = int]':
<source>:16:6:   required from here
<source>:6:24: error: conflicting declaration 'struct a<
<template-parameter-1-1> >::a() [with <template-parameter-1-1> = int]::c'
     } catch (struct c {}) {
                        ^
<source>:4:12: note: previous declaration as 'struct a<
<template-parameter-1-1> >::a() [with <template-parameter-1-1> = int]::c'
     struct c;
            ^
<source>:6: confused by earlier errors, bailing out
Compiler returned: 1

Test case was reduced by C-Reduce.