[Bug c++/84182] New: [8 Regression] ICE in variadic lambda inside a template when calling a captured lambda

[benni.buch at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84182

            Bug ID: 84182
           Summary: [8 Regression] ICE in variadic lambda inside a
                    template when calling a captured lambda
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: benni.buch at gmail dot com
  Target Milestone: ---

template < typename ... T > void sink(T ...){}

template < typename >
void f(){
    auto const lambda = [](int){ return 1; };

    [lambda](auto ... i){
        sink(lambda(i) ...);
    }(1);
}

int main(){
    f< int >();
}


$ g++ -std=c++14 main.cpp                                                       
main.cpp: In instantiation of 'f() [with <template-parameter-1-1> =
int]::<lambda(auto:1 ...)> [with auto:1 = {int}]':
main.cpp:9:6:   required from 'void f() [with <template-parameter-1-1> = int]'
main.cpp:13:14:   required from here
main.cpp:7:24: internal compiler error: in lookup_template_class_1, at
cp/pt.c:8957
     [lambda](auto ... i){
                        ^
0x612f6a lookup_template_class_1                                                
        ../../gcc/gcc/cp/pt.c:8957                                              
0x612f6a lookup_template_class(tree_node*, tree_node*, tree_node*, tree_node*,
int, int)                                                                       
        ../../gcc/gcc/cp/pt.c:9167                                              
0x940d5a tsubst_aggr_type                                                       
        ../../gcc/gcc/cp/pt.c:12073                                             
0x93873f tsubst_copy                                                            
        ../../gcc/gcc/cp/pt.c:14845                                             
0x92711d tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:18059
0x93a8e4 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:14365
0x93a8e4 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:14365
0x941873 tsubst_decl
        ../../gcc/gcc/cp/pt.c:13111
0x939eef tsubst_copy
        ../../gcc/gcc/cp/pt.c:14890
0x925ee0 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:18266
0x9275de tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17663
0x934e49 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17100
0x934e49 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16838
0x9436b2 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16030
0x9436b2 gen_elem_of_pack_expansion_instantiation
        ../../gcc/gcc/cp/pt.c:11175
0x9436b2 tsubst_pack_expansion(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:11683
0x927ded tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17684
0x934e49 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:17100
0x934e49 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16838
0x933970 tsubst_expr(tree_node*, tree_node*, int, tree_node*, bool)
        ../../gcc/gcc/cp/pt.c:16059
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.


$ g++ --version
g++ (GCC) 8.0.1 20180202 (experimental)
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.



Known to work with GCC 6.3 and 5.4:

$ g++-6 --version
g++-6 (Ubuntu/Linaro 6.3.0-18ubuntu2~16.04) 6.3.0 20170519
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++-5 --version
g++-5 (Ubuntu 5.4.1-2ubuntu1~16.04) 5.4.1 20160904
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.