[Bug c++/68434] New: [concepts] ICE same canonical type node for different types

["ryan.burn at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68434

            Bug ID: 68434
           Summary: [concepts] ICE same canonical type node for different
                    types
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ryan.burn at gmail dot com
  Target Milestone: ---

The code below generates this ICE when compiled with 

g++ (GCC) 6.0.0 20151118 (experimental)

 constexpr bool C1() constexpr bool C2() constexpr bool C3()
reduce2.cpp: At global scope:
reduce2.cpp:19:10: internal compiler error: same canonical type node for
different types C2 and C1
 auto f(C3) {
          ^

0x8fb760 comptypes(tree_node*, tree_node*, int)
        ../../src-orig/gcc/cp/typeck.c:1435
0x9857e8 cp_tree_equal(tree_node*, tree_node*)
        ../../src-orig/gcc/cp/tree.c:3128
0x9857a1 cp_tree_equal(tree_node*, tree_node*)
        ../../src-orig/gcc/cp/tree.c:3121
0x9857a1 cp_tree_equal(tree_node*, tree_node*)
        ../../src-orig/gcc/cp/tree.c:3121
0xa17928 insert
        ../../src-orig/gcc/cp/logic.cc:131
0xa17c8d left_conjunction
        ../../src-orig/gcc/cp/logic.cc:237
0xa17e6d decompose_left_term
        ../../src-orig/gcc/cp/logic.cc:292
0xa17f07 decompose_left_goal
        ../../src-orig/gcc/cp/logic.cc:315
0xa17f5d decompose_left
        ../../src-orig/gcc/cp/logic.cc:327
0xa18179 decompose_assumptions(tree_node*)
        ../../src-orig/gcc/cp/logic.cc:373
0xa12af0 build_constraints(tree_node*, tree_node*)
        ../../src-orig/gcc/cp/constraint.cc:1035
0x780e0f grokfndecl
        ../../src-orig/gcc/cp/decl.c:7819
0x78c25d grokdeclarator(cp_declarator const*, cp_decl_specifier_seq*,
decl_context, int, tree_node**)
        ../../src-orig/gcc/cp/decl.c:11292
0x79f2c9 start_function(cp_decl_specifier_seq*, cp_declarator const*,
tree_node*)
        ../../src-orig/gcc/cp/decl.c:14069
0x8bd2c1 cp_parser_function_definition_from_specifiers_and_declarator
        ../../src-orig/gcc/cp/parser.c:24703
0x8b09bd cp_parser_init_declarator
        ../../src-orig/gcc/cp/parser.c:17972
0x8a6d64 cp_parser_simple_declaration
        ../../src-orig/gcc/cp/parser.c:11971
0x8a6b22 cp_parser_block_declaration
        ../../src-orig/gcc/cp/parser.c:11843
0x8a689c cp_parser_declaration
        ../../src-orig/gcc/cp/parser.c:11740
0x8a63a7 cp_parser_declaration_seq_opt
        ../../src-orig/gcc/cp/parser.c:11619
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions

//////////////////////////////////////////////////////////////
template <class>                                                                
concept bool C1() {                                                             
  return true;                                                                  
}                                                                               

template <class>                                                                
concept bool C2() {                                                             
  return true;                                                                  
}                                                                               

template <class Expr>                                                           
concept bool C3() {                                                             
  return requires(Expr expr) {                                                  
      {expr}->C1;                                                               
      {expr}->C2;                                                               
  };                                                                            
}                                                                               

auto f(C3) {                                                                    
} 
//////////////////////////////////////////////////////////////