[Issue 12936] New: Some more @nogc cases for immediately iterated array literal

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=12936

          Issue ID: 12936
           Summary: Some more @nogc cases for immediately iterated array
                    literal
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: DMD
          Assignee: nob...@puremagic.com
          Reporter: bearophile_h...@eml.cc

This is a spinoff of Issue 12932


See this code:


struct F { int x; }
void main() @nogc {
    foreach (       a; [F(1)]) {}           // Case#1 OK
    foreach (int[1] a; [[1]]) {}            // Case#2 Error
    foreach (const ref int[1] a; [[1]]) {}  // Case#3 Error
    foreach (       a; [[1]]) {}            // Case#4 Error
}



With dmd2.066alpha gives:

test.d(4,25): Error: array literal in @nogc function main may cause GC
allocation
test.d(5,5): Error: argument type mismatch, int[] to ref const(int[1])
test.d(6,25): Error: array literal in @nogc function main may cause GC
allocation


Currently the Case#1 works. I think Case#2 could work because it's supposed to
be a dynamic array of int[1] values.

I am not sure we can also support the Case#4, this is more complex, and perhaps
needs escape analisys. So not supporting Case#4 is acceptable for now.

Case#4 currently doesn't even compile even without @nogc, but perhaps it should
without @nogc.

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