fn example<T>(data []T) [][]T causes panic with compiler bug in explanation

[natemcintosh]

$ v doctor
OS: macos, Mac OS X, 10.15.6, 19G2531
Processor: 8 cpus, 64bit, little endian, Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz
CC version: Apple clang version 12.0.0 (clang-1200.0.32.28)

getwd: /Users/natemcintosh/Documents/dev/vlang_examples
vmodules: /Users/natemcintosh/.vmodules
vroot: /Users/natemcintosh/Documents/dev/v
vexe: /Users/natemcintosh/Documents/dev/v/v
vexe mtime: 2020-12-31 13:38:23
is vroot writable: true
is vmodules writable: true
V full version: V 0.2.1 3e655d6.f7b3ed2

Git version: git version 2.24.3 (Apple Git-128)
Git vroot status: 0.2-195-gf7b3ed2f (1 commit(s) behind V master)
.git/config present: true
thirdparty/tcc status: thirdparty-macos-amd64 689c8a02

What did you do?
In a file example.v

fn example<T>(data []T) [][]T {
	return [data]
}

fn main() {
	data := [1, 2, 3]
	d2 := example(data)
	println('$d2') // comment this line out and the crash does not occur
}

run v run example.v

What did you expect to see?
[[1, 2, 3]]

What did you see instead?

V panic: get_type_symbol: invalid type (typ=0 idx=0). Compiler bug. This should never happen. Please create a GitHub issue.

0   v                                   0x0000000107734ea0 v__table__Table_get_type_symbol + 128
1   v                                   0x00000001077b86ae v__gen__Gen_cc_type + 62
2   v                                   0x00000001077b8245 v__gen__Gen_base_type + 69
3   v                                   0x000000010779fb1b v__gen__Gen_typ + 27
4   v                                   0x00000001077ab10b v__gen__Gen_gen_str_for_array + 123
5   v                                   0x00000001077aa51a v__gen__Gen_gen_str_for_type + 938
6   v                                   0x00000001077ab387 v__gen__Gen_gen_str_for_array + 759
7   v                                   0x00000001077aa51a v__gen__Gen_gen_str_for_type + 938
8   v                                   0x00000001077ca9f1 v__gen__Gen_gen_expr_to_string + 1201
9   v                                   0x00000001077da83d v__gen__Gen_string_inter_literal + 3437
10  v                                   0x00000001077a246d v__gen__Gen_expr + 9853
11  v                                   0x00000001077e8e22 v__gen__Gen_call_args + 1634
12  v                                   0x00000001077e8751 v__gen__Gen_fn_call + 4753
13  v                                   0x00000001077ce7db v__gen__Gen_call_expr + 1131
14  v                                   0x000000010779ffe5 v__gen__Gen_expr + 501
15  v                                   0x00000001077ba293 v__gen__Gen_stmt + 2595
16  v                                   0x00000001077b959b v__gen__Gen_stmts_with_tmp_var + 363
17  v                                   0x00000001077b3ae3 v__gen__Gen_stmts + 83
18  v                                   0x00000001077c3501 v__gen__Gen_gen_fn_decl + 6001
19  v                                   0x00000001077ba883 v__gen__Gen_stmt + 4115
20  v                                   0x00000001077b959b v__gen__Gen_stmts_with_tmp_var + 363
21  v                                   0x00000001077b3ae3 v__gen__Gen_stmts + 83
22  v                                   0x00000001077b1be1 v__gen__cgen + 4529
23  v                                   0x0000000107804805 v__builder__Builder_gen_c + 549
24  v                                   0x0000000107804ed7 v__builder__Builder_build_c + 295
25  v                                   0x00000001078052de v__builder__Builder_compile_c + 846
26  v                                   0x000000010780ffb3 v__builder__compile + 339
27  v                                   0x0000000107814777 main__main + 4359
28  v                                   0x0000000107816d7e main + 78
29  v                                   0x00000001076dc754 start + 52
30  ???                                 0x0000000000000003 0x0 + 3

[natemcintosh]

It seems like the issue has changed, but that there still is an issue.

v doctor gives

$ v doctor
OS: macos, Mac OS X, 10.15.6, 19G2531
Processor: 8 cpus, 64bit, little endian, Intel(R) Core(TM) i7-4850HQ CPU @ 2.30GHz
CC version: Apple clang version 12.0.0 (clang-1200.0.32.28)

getwd: /Users/natemcintosh/Documents/dev/vtesting
vmodules: /Users/natemcintosh/.vmodules
vroot: /Users/natemcintosh/Documents/dev/v
vexe: /Users/natemcintosh/Documents/dev/v/v
vexe mtime: 2021-01-06 23:51:36
is vroot writable: true
is vmodules writable: true
V full version: V 0.2.1 9593ad2

Git version: git version 2.24.3 (Apple Git-128)
Git vroot status: 0.2-330-g9593ad20
.git/config present: true
thirdparty/tcc status: thirdparty-macos-amd64 689c8a02

What did you do?

// testing.v
fn main() {
	d11 := [1, 2, 3]
	d12 := example(d11)
	println('$d11 -> $d12')
	d21 := [1., 2., 3.]
	d22 := example(d21)
	println('$d21 -> $d22')
	d31 := ['hello', 'my', 'name', 'is']
	d32 := example(d31)
	println('$d31 -> $d32')
}

fn example<T>(data []T) [][]T {
	return [data]
}

and at the command line v run testing.v

What did you expect to see?

[1, 2, 3] -> [[1, 2, 3]]
[1, 2, 3] -> [[1, 2, 3]]
['hello', 'my', 'name', 'is'] -> [['hello', 'my', 'name', 'is']]

What did you see instead?

[1, 2, 3] -> [4]
[1, 2, 3] -> [1.39071e-309]
Terminated by signal 11 (SIGSEGV)

[natemcintosh]

This no longer seems to be an issue