String literal shorter than n is quietly coerced into *const [n]u8

[boomlinde]

Zig Version

0.14.0-dev.2577+271452d22

Steps to Reproduce and Observed Behavior

test "String literal shorter than n is quietly coerced into *const [n]u8" {
    const alphabet: *const [64]u8 = "A";
    @import("std").debug.print("{s}\n", .{alphabet});
}

This will produce output that contains the string literal followed by random string data presumably present after the literal in memory.

Expected Behavior

I expected and would prefer that this fails at compile time. It makes some sense to me that a longer string literal would coerce into a pointer to a shorter string (which is also the case), but not the other way around, especially not in a way that places some undefined data in the array.

Happy Gregorian new year!

[mlugg]

Bug is in Sema.coerceInMemoryAllowedPtrs; the special path for coercing array pointers while dropping the sentinel fails to check the array length. I'll try and get a fix up tomorrow.