Rather than `Zcu.BuiltinDecl.Memoized` being a struct with fields, it
can instead just be an array, indexed by the enum. This allows runtime
indexing, avoiding a few now-unnecessary `inline` switch cases.
This commit reworks how values like the panic handler function are
memoized during a compiler invocation. Previously, the value was
resolved by whichever analysis requested it first, and cached on `Zcu`.
This is problematic for incremental compilation, as after the initial
resolution, no dependencies are marked by users of this memoized state.
This is arguably acceptable for `std.builtin`, but it's definitely not
acceptable for the panic handler/messages, because those can be set by
the user (`std.builtin.Panic` checks `@import("root").Panic`).
So, here we introduce a new kind of `AnalUnit`, called `memoized_state`.
There are 3 such units:
* `.{ .memoized_state = .va_list }` resolves the type `std.builtin.VaList`
* `.{ .memoized_state = .panic }` resolves `std.Panic`
* `.{ .memoized_state = .main }` resolves everything else we want
These units essentially "bundle" the resolution of their corresponding
declarations, storing the results into fields on `Zcu`. This way, when,
for instance, a function wants to call the panic handler, it simply runs
`ensureMemoizedStateResolved`, registering one dependency, and pulls the
values from the `Zcu`. This "bundling" minimizes dependency edges. The 3
units are separated to allow them to act independently: for instance,
the panic handler can use `std.builtin.Type` without triggering a
dependency loop.
`Zcu.PerThead.ensureTypeUpToDate` is set up in such a way that it only
returns the updated type the first time it is called. In general, that's
okay; however, the exception is that we want the function to continue
returning `error.AnalysisFail` when the type has been lost, or its
number of captures changed.
Therefore, the check for this case now happens before the up-to-date
success return.
For simplicity, the number of captures is now handled by intentionally
losing the instruction in `Zcu.mapOldZirToNew`, since there is nothing
to gain from tracking a type when old instances of it can never be
reused.
The old lowering was kind of neat, but it unintentionally allowed the
syntax `for (123) |_| { ... }`, and there wasn't really a way to fix
that. So, instead, we include both the start and the end of the range in
the `for_len` instruction (each operand to `for` now has *two* entries
in this multi-op instruction). This slightly increases the size of ZIR
for loops of predominantly indexables, but the difference is small
enough that it's not worth complicating ZIR to try and fix it.
Previously, logic in `Compilation.getAllErrorsAlloc` was corrupting the
`failed_analysis` hashmap. This meant that on updates after the initial
update, attempts to remove entries from this map (because the `AnalUnit`
in question is being re-analyzed) silently failed. This resulted in
compile errors from earlier updates wrongly getting "stuck", i.e. never
being removed.
This commit also adds a few log calls which helped me to find this bug.
Most calls to `requireRuntimeBlock` in Sema are not correct. This
function doesn't deal with all of them, but it does deal with ones which
have, in combination with the past few commits, introduced real-world
regressions.
Related: #22353
Some sub-expressions should always be evaluated at comptime -- in
particular, type expressions, e.g. `E` in `E!T`. However, bugs in this
logic are easy to miss, because the parent scope is usually comptime
anyway!
This fixes a bug which exposed a compiler implementation detail (ZIR
alloc elision). Previously, `const` declarations with a runtime-known
value in a comptime scope were permitted only if AstGen was able to
elide the alloc in ZIR, since the error was reported by storing to the
comptime alloc.
This just adds a new instruction to also emit this error when the alloc
is elided.
To avoid this PR regressing error messages, most of the work here has
gone towards improving error notes for why code was comptime-evaluated.
ZIR `block_comptime` now stores a "comptime reason", the enum for which
is also used by Sema. There are two types in Sema:
* `ComptimeReason` represents the reason we started evaluating something
at comptime.
* `BlockComptimeReason` represents the reason a given block is evaluated
at comptime; it's either a `ComptimeReason` with an attached source
location, or it's because we're in a function which was called at
comptime (and that function's `Block` should be consulted for the
"parent" reason).
Every `Block` stores a `?BlockComptimeReason`. The old `is_comptime`
field is replaced with a trivial `isComptime()` method which returns
whether that reason is non-`null`.
Lastly, the handling for `block_comptime` has been simplified. It was
previously going through an unnecessary runtime-handling path; now, it
is a trivial sub block exited through a `break_inline` instruction.
Resolves: #22296
