Similar to the previous commit, errors coercing the panic message to
`[]const u8` now point at the operand to `@panic` rather than the actual
builtin call.
When coercing the operand of a `ret_node` etc instruction, the source
location for errors used to point to the entire `return` statement.
Instead, we now point to the operand, as would be expected if there was
an explicit `as_node` instruction (like there used to be).
Previously, the `src_node` field of `struct_decl`, `union_decl`,
`enum_decl`, and `opaque_decl` was optional, included in trailing data
only if a flag in `Small` was set. However, this was unnecessary logic:
AstGen always provided the source node. We can simplify a few bits of
logic by making this field non-optional, moving it into non-trailing
data.
There was one place where the field was actually omitted before: the
root struct of a file was at source node 0, so the node was
coincidentally elided. Therefore, this commit has a fixed cost of 4
bytes of ZIR per file.
In most cases where AstGen is coercing to a fixed type (such as `u29`,
`type`, `std.builtin.CallingConvention) we do not necessarily require an
explicit coercion instruction. Instead, Sema knows the type that is
required, and can perform the coercion after the fact. This means we can
use the `coerced_ty` result location kind, saving unnecessary coercion
instructions and therefore ZIR bytes.
This required a few enhancements to Sema to introduce missing coercions.
`sema.src` is a failed experiment. It introduces complexity, and makes
often unwarranted assumptions about the existence of instructions
providing source locations, requiring an unreasonable amount of caution
in AstGen for correctness. Eliminating it simplifies the whole frontend.
This required adding source locations to a few instructions, but the
cost in ZIR bytes should be counteracted by the other work on this
branch.
AstGen has logic to elide leading `dbg_stmt` instructions when multiple
are emitted consecutively; however, it only applied in some cases. A
simple reshuffle here makes this logic apply universally, saving some
bytes in ZIR.
This is a small optimization to generated ZIR. In any function where the
return type is not a trivial Ref, we know it is almost certainly not
`void` (unless the user aliased it or did something else weird to fool
AstGen), and thus the return type is very likely to be required for
return value RLS at some point. Thus, we can just emit one `ret_type` at
the start of the function and use it throughout.
This sees a very small improvement in overall ZIR bytes.
It was usefull during development.
From andrewrk code review comment:
In fact, Zig does not guarantee the @sizeOf structs, and so these tests are not valid.
Encountered in a recent CI run on an aarch64-windows dev kit.
Pretty sure I disabled the virus scanner but it looks like it turned
itself back on with a Windows Update.
Rather than marking the new error code as unreachable in the places
where it is unexpected, this commit makes it return `error.Unexpected`.
