Well, this was a journey!
The original issue I was trying to fix is covered by the new behavior
test in array.zig: in essence, `ty` and `coerced_ty` result locations
were not correctly propagated.
While fixing this, I noticed a similar bug in struct inits: the type was
propagated to *fields* fine, but the actual struct init was
unnecessarily anonymous, which could lead to unnecessary copies. Note
that the behavior test added in struct.zig was already passing - the bug
here didn't change any easy-to-test behavior - but I figured I'd add it
anyway.
This is a little harder than it seems, because the result type may not
itself be an array/struct type: it could be an optional / error union
wrapper. A new ZIR instruction is introduced to unwrap these.
This is also made a little tricky by the fact that it's possible for
result types to be unknown at the time of semantic analysis (due to
`anytype` parameters), leading to generic poison. In these cases, we
must essentially downgrade to an anonymous initialization.
Fixing these issues exposed *another* bug, related to type resolution in
Sema. That issue is now tracked by #16603. As a temporary workaround for
this bug, a few result locations for builtin function operands have been
disabled in AstGen. This is technically a breaking change, but it's very
minor: I doubt it'll cause any breakage in the wild.
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
Also remove an incorrect piece of logic which allowed fetching the 'len'
property on non-single-ptrs (e.g. many-ptrs) and add a corresponding
compile error test case.
Resolves: #4765
Previously, if you had a pointer to multiple array elements and tried to
write to it at comptime, it was incorrectly treated as a pointer to one
specific array value, leading to an assertion down the line. If we try
to mutate a value at an elem_ptr larger than the element type, we need
to perform a modification to multiple array elements.
This solution isn't ideal, since it will result in storePtrVal
serializing the whole array, modifying the relevant parts, and storing
it back. Ideally, it would only take the required elements. However,
this change would have been more complex, and this is a fairly rare
operation (nobody ever ran into the bug before after all), so it doesn't
matter all that much.
It did not handle properly when the dummy operand was a comptime_int; it
was crashing in coerce because comptime_int is supposed to be
comptime-known. So when calling coerceResultPtr, we pass the actual
operand, not a dummy operand, which means it will have the proper
comptime value when necessary.
Split big test into the two separate things it is testing.
Add missing checks to the test which revealed the test is not actually
passing yet for the C backend.
Adds the sentinel element to the type name to avoid ambiguous
declarations, and outputs the sentinel element (if needed) even in what
would otherwise be empty arrays.
