missing notes on compile error

[lun-4]

This code

pub const XML_ElementDeclHandler = ?extern fn ([*c]const u8, [*c][*c]const u8) void;
pub extern fn XML_SetElementDeclHandler(eldecl: XML_ElementDeclHandler) void;

extern fn someOtherFunction(a: [*]const u8, b: [*][*]const u8) void {
    return;
}

pub fn main() void {
    XML_SetElementDeclHandler(someOtherFunction);
}

gives the following:

test36.zig:9:31: error: expected type '?extern fn([*c]const u8, [*c][*c]const u8) void', found 'extern fn([*]const u8, [*][*]const u8) void'
    XML_SetElementDeclHandler(someOtherFunction);
                              ^

A big help could be adding notes to help the writer that they should use optionals e.g ?[*]const u8. For example, the last note on this snippet

From IRC:

[17:51] < andrewrk> lunamn, yes, in fact I'm pretty sure it's a TODO in the compiler already, just needs a bit of glue code to wire that up

[Vexu]

Now gives:

a.zig:9:31: error: expected type '*const fn([*c]const u8, [*c][*c]const u8) callconv(.C) void', found '*const fn([*]const u8, [*][*]const u8) callconv(.C) void'
    XML_SetElementDeclHandler(someOtherFunction);
                              ^~~~~~~~~~~~~~~~~
a.zig:9:31: note: pointer type child 'fn([*]const u8, [*][*]const u8) callconv(.C) void' cannot cast into pointer type child 'fn([*c]const u8, [*c][*c]const u8) callconv(.C) void'
a.zig:9:31: note: parameter 0 '[*]const u8' cannot cast into '[*c]const u8'
a.zig:9:31: note: '[*c]const u8' could have null values which are illegal in type '[*]const u8'
referenced by:
    callMain: zig-out/lib/zig/std/start.zig:604:17
    initEventLoopAndCallMain: zig-out/lib/zig/std/start.zig:548:34
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

Plenty of tests can be found by grepping for any of those errors.