[Bug c++/85076] New: [6/7/8 Regression] ICE with invalid template used as lambda argument

[reichelt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85076

            Bug ID: 85076
           Summary: [6/7/8 Regression] ICE with invalid template used as
                    lambda argument
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: error-recovery, ice-on-invalid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org
  Target Milestone: ---

The following invalid code snippet triggers an ICE since GCC 6.2.0:

==================================
template<typename> struct A*;

auto a = [](A<auto>) {};
==================================

bug.cc:1:29: error: expected unqualified-id before ';' token
 template<typename> struct A*;
                             ^
bug.cc:3:13: error: 'A' is not a template
 auto a = [](A<auto>) {};
             ^
bug.cc:3:13: error: '<anonymous>' has incomplete type
 auto a = [](A<auto>) {};
             ^~~~~~~
bug.cc:1:27: note: forward declaration of 'struct A'
 template<typename> struct A*;
                           ^
bug.cc:3:23: internal compiler error: tree check: expected reference_type, have
error_mark in cp_build_reference_type, at cp/tree.c:1099
 auto a = [](A<auto>) {};
                       ^
0x78c502 tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ../../gcc/gcc/tree.c:9322
0x664299 tree_check(tree_node*, char const*, int, char const*, tree_code)
        ../../gcc/gcc/tree.h:3135
0x664299 cp_build_reference_type(tree_node*, bool)
        ../../gcc/gcc/cp/tree.c:1099
0x8f4696 forward_parm(tree_node*)
        ../../gcc/gcc/cp/method.c:472
0x8dd6be maybe_add_lambda_conv_op(tree_node*)
        ../../gcc/gcc/cp/lambda.c:1125
0x924fc2 cp_parser_lambda_expression
        ../../gcc/gcc/cp/parser.c:10201
0x924fc2 cp_parser_primary_expression
        ../../gcc/gcc/cp/parser.c:5263
0x937c0c cp_parser_postfix_expression
        ../../gcc/gcc/cp/parser.c:7032
0x9387e0 cp_parser_unary_expression
        ../../gcc/gcc/cp/parser.c:8324
0x9186df cp_parser_cast_expression
        ../../gcc/gcc/cp/parser.c:9092
0x918eea cp_parser_binary_expression
        ../../gcc/gcc/cp/parser.c:9193
0x91a724 cp_parser_assignment_expression
        ../../gcc/gcc/cp/parser.c:9488
0x91987b cp_parser_constant_expression
        ../../gcc/gcc/cp/parser.c:9772
0x91a6a7 cp_parser_initializer_clause
        ../../gcc/gcc/cp/parser.c:21929
0x91cf62 cp_parser_initializer
        ../../gcc/gcc/cp/parser.c:21869
0x93c3ae cp_parser_init_declarator
        ../../gcc/gcc/cp/parser.c:19684
0x943758 cp_parser_simple_declaration
        ../../gcc/gcc/cp/parser.c:13059
0x944568 cp_parser_block_declaration
        ../../gcc/gcc/cp/parser.c:12884
0x9484c2 cp_parser_declaration
        ../../gcc/gcc/cp/parser.c:12782
0x9488d1 cp_parser_declaration_seq_opt
        ../../gcc/gcc/cp/parser.c:12658
Please submit a full bug report, [etc.]