There are a couple concepts here worth understanding:
Key.UnionType - This type is available *before* resolving the union's
fields. The enum tag type, number of fields, and field names, field
types, and field alignments are not available with this.
InternPool.UnionType - This one can be obtained from the above type with
`InternPool.loadUnionType` which asserts that the union's enum tag type
has been resolved. This one has all the information available.
Additionally:
* ZIR: Turn an unused bit into `any_aligned_fields` flag to help
semantic analysis know whether a union has explicit alignment on any
fields (usually not).
* Sema: delete `resolveTypeRequiresComptime` which had the same type
signature and near-duplicate logic to `typeRequiresComptime`.
- Make opaque types not report comptime-only (this was inconsistent
between the two implementations of this function).
* Implement accepted proposal #12556 which is a breaking change.
This will do zig run on the code and expect exit code 0.
// run
Incremental Compilation
Make multiple files that have ".", and then an integer, before the ".zig"
extension, like this:
hello.0.zig
hello.1.zig
hello.2.zig
Each file can be a different kind of test, such as expecting compile errors,
or expecting to be run and exit(0). The test harness will use these to simulate
incremental compilation.
At the time of writing there is no way to specify multiple files being changed
as part of an update.
Subdirectories
Subdirectories do not have any semantic meaning but they can be used for
organization since the test harness will recurse into them. The full directory
path will be prepended as a prefix on the test case name.
Limiting which Backends and Targets are Tested
// run
// backend=stage2,llvm
// target=x86_64-linux,x86_64-macos
Possible backends are:
stage1: equivalent to -fstage1.
stage2: equivalent to passing -fno-stage1 -fno-LLVM.
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