[Issue 15752] New: Diagnostic: Better Error Message for Assigning Incorrect AA Empty Value

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15752

          Issue ID: 15752
           Summary: Diagnostic: Better Error Message for Assigning
                    Incorrect AA Empty Value
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: jack at jackstouffer.com

Because of the use of [] to enclose AA assignment, one could be forgiven in
accidentally doing something like this:

void main() {
    int[int] a = [];
}

Which results in the very unhelpful message:

Error: can't have associative array key of void

Of course, the right answer is to use null, but again, the similarities with
array literals one could be expected to make this mistake. The error message is
also different when trying to do this for an optional function parameter.

void func(int[int] b = []) {
}

void main() {
    func();
}

Error: cannot implicitly convert expression ([]) of type void[] to int[int]

The message should be something like this: 

Error: can't have associative array key of void. Perhaps you meant to
initialize an empty AA with null?

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