When a class extends an interface, referring to a member name of the
interface as an unqualified name should refer to the class's
corresponding associated entity value, not to the associated entity
itself. Similarly, in an `impl`, unqualified names of associated
entities should refer to the `impl`'s corresponding value for that
entity.
To support this, we treat `impl`s as `extend`ing their implemented facet
type, and we make lookups into an extended facet type use the `Self`
type of the extending `impl` or `class` if lookup finds an associated
entity. We already did the latter if the extending entity was an
interface; this extends the existing support for these other cases.
A nested designator like `.(X.X1).(Y.Y1)` results in nested
ImplWitnessAccess instructions, which can produce cycles in the
toolchain easily when replacing `.Self`.
First, when constructing a facet type like `V:! Z where .Z1 impls (Y
where .Y1 = U)` we substitute replace `.Self` in the nested facet type,
and in this case we replace `.Self` with `.Z1` which contains a `.Self`
of its own. This was coming from us being lazy about replacing `.Self`
in an `impl as` declaration, such as `impl C as Z where .Z1 = .Self`.
The self type is known there, so we can more eagerly replace `.Self` as
we do in a `require impls` declaration. Then the replacement for `.Self`
never comes with a `.Self` that needs to also be replaced. Any resulting
`.Self` would always be the top-level one.
Second, when evaluating ImplWitnessAccess, we were replacing .Self in
the LHS of rewrite constraints, but the `.Self` may itself have a type
that contains rewrite constraints. If one of those rewrite constraints
has nested ImplWitnessAccess instructions, we evaluate the new
ImplWitnessAccess, which again finds rewrite constraints to replace
`.Self` in, and we repeat forever. For this one we just stop replacing
.Self in the LHS of rewrite constraints. Since they are always against
.Self, we can always look in the access facet's type for a value.
While fixing ImplWitness access, also correct the lookup to search
through the types of nested ImplWitnessAccess instructions to find a
rewrite value, since it may find it at any level up to the eventual
`.Self`.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This lets us stop eliding it in textual semir tests with dump ranges.
Previously it would always get elided, even though it was part of the
range being dumped, and was referred to by other instructions in the
dump range.
Since each `.Self` is unique (can change its type if not its value) in a
facet type, having each one distinct by location also aids
understanding.
A `where` expression nested inside a `T impls X` constraint makes
`.Self` ambiguous on the right-hand side of the `where` if `T` is
anything other than `.Self`. After the `where`, the value of a `.Self`
could be `T` or could be the value of `.Self` before the `impls`
constraint: the so-called top-level value of `.Self`.
Implicit use of `.Self` in designators is always allowed, and they are
bound (and replaced by a reference) to the inner-most possible value of
`.Self`. On the right-hand side of the nested `where` above, they have
the value `T as X`.
`.Self impls ...` is also always allowed, since it acts more as a
keyword here, and it always refers to the inner-most possible value of
`.Self`.
Any other explicit use of `.Self` is diagnosed when ambiguous, in any
kind of constraint. This is done in the handling of `WhereExpr` since it
has enough context to allow `.Self impls` (which is an explicit use)
while disallowing other explicit uses. And because it has non-canonical
instructions to work with, so it is able to diagnose errors with precise
locations.
Since `.Self` is no longer going to be marked with depth modifiers, the
eval of `WhereExpr` does not need an input facet value instruction
representing `.Self` to compare with, as they are now going to all be
equivalent. So revert it back to just looking for the `PeriodSelf` name
id, through a shared helper being introduced as `IsPeriodSelf`. And drop
the period self InstId from the `WhereExpr` instruction. This causes
most of the formatted SemIR changes.
Move helpers for working with and replacing `.Self` to their own file,
out of the `facet_type.h` header/cpp files. These are working with
`.Self` facet values more than facet types, though `.Self` is a name
that only exists inside the scope of a facet type.
Implementation of unused pattern bindings #2022, continued.
Whereas previous PR #6460 took care of parsing, and PR #6479 prepared
the stage by using _ in some test cases, this PR has the the actual
implementation, using a simple dataflow analysis.
---------
Co-authored-by: Burak Emir <bqe@google.com>
Co-authored-by: jonmeow <jperkins@google.com>
This gets us a step closer toward resolving TODOs in member access
around facets, by making the lookup into a facet value a "lookup in
base" operation instead of a "lookup in type of base". However the base
given to find scopes in still remains the facet type of the facet, which
is still a TODO.
Then we can simplify the "lookup in type of base" case a bit, with a
single code path doing the name lookup step. But we keep a TODO where if
the type of base is a facet, we change the lookup target to be the facet
type of the facet instead.
This is toward having name lookup into an interface that is extending a
named constraint work correctly with a `Self` in its specific. To
perform that name lookup, we will need to tell name lookup what is the
base, so that it can replace `Self` with the base. This change gets us
in a position where we can correctly provide the base in the `T.F()`
(lookup in facet) and `t.F()` (lookup in type of facet) correctly and
straightforwardly.
We provide a marginally improved diagnostic when looking into a facet
with an incomplete facet type, which will move into
AppendLookupScopesForConstant once we are looking into the facet
directly instead of its type.
Give TupleLiteral and StructLiteral a constant value, if their contents
have constant values. Their constant values are TupleValue and
StructValue respectively. This supports their ability to convert to a
constant type (or facet type).
This way when deduce finds a TupleLiteral as the argument to a
_symbolic_ facet type, it can also find a constant value to use for that
argument. This allows deduction to move onto step two, where it can
substitute into the symbolic parameter from previous deduced arguments,
and then perform the conversion from the TupleValue to the desired facet
type.
Allow `PerformBuiltinConversion()` to convert from a canonical
TupleValue or StructValue to `type` instead of only from literals. Then,
also support conversion from a symbolic binding of type TupleType or
StructType to `type`.
The SymbolicBindingType refers to the type value that will be
substituted in for the BindSymbolicName, but holds onto the EntityNameId
from the BindSymbolicName instead of (or in addition to, for now) the
instruction.
The EntityNameId will be used to look in the ScopeStack to find the
witnesses either from the BindSymbolicName instruction, or other
instructions that specify `impls` constraints against the EntityName.
This will allow us to have the `T` in `I(T)` resolve to a `.Self`
reference in the type so that we get type equality with the binding's
type: `T:! I(.Self)`.
Decouples associated constants from being special cased in let handlers.
Enforces associated constant grammar restrictions in parsing instead of
checking.
Closes#5411
We add a virtual node (`CompileTimeBindingPatternStart`) as the first
child of `CompileTimeBindingPattern` which holds the identifier
underneath it, so that it is checked just before the type expression of
the `CompileTimeBindingPattern`. When we reach this virtual node during
check, we add `.Self` as a name in the current scope, and when we reach
`CompileTimeBindingPattern` we remove it from scope, which ensures it's
present during only the checking of the type expression for the compile
time pattern.
At the moment the `.Self` has a different type (it's a `TypeType`) than
other `.Self` in the facet type (which are a single `FacetType`), but
the intention is to immediately substitute it out of the facet type
entirely, replacing it with a reference to the compile time binding (a
`BindSymbolicName`) itself. A TODO has been added for this.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
This makes all `.Self` references in a facet type canonically the same
(which will remain true iff they refer to the same `Self` type in the
future), removing the need to do more complex comparisons between them
using the EntityName, interface, and index. This allows the comparison
of types containing `.Self` references to be done correctly regardless
of where the `.Self` appears, as such type expressions will all be
canonically equal if they otherwise equal now, regardless of whether
they are written in the context where `.Self` could have seen different
`Self` facet types.
In order to retain access to constraints on a base `.Self` facet type,
in the case of applying `where` to an existing facet type, we:
- Give the base facet type as a `RequirementBaseFacetType` constraint so
that eval of `WhereExpr` can find and copy all the constraints off of
it.
- Introduce eager/early rewrite constraint resolution, which allows a
constraint to eagerly resolve access to earlier rewrite constraints
(`where .A = () and .B = .A` is eagerly transformed into `where .A = ()
and .B = ()`) before the full constraint resolution step. This allows
use of rewrite constraints in larger type expressions, such as `where .A
= () and .B = C(.A)` and `C` will know that the argument is `()`.
In order to verify rewrite constraints at the end of
`LookupImplWitness()` we need to replace references to associated
constants in the query facet type with values that come from the query's
self. To do this, we find any `ImplWitnessAccess` that is a reference to
`.Self` and replace its witness with the witness found through the impl
lookup process, if the interfaces match. This allows the
`ImplWitnessAccess` to resolve to a concrete value if that witness was
concrete. Then we just need to compare that for each rewrite constraint
the lhs and rhs are the same constant value. If they differ, the self
provided a different value for one side (either through its own facet
value constraints or through an associated impl), or the self did not
provide a value at all.
For now, only .Self references in the top-level facet type are
rewritten. Nested facet types are not, even if they contain a .Self
reference up to the top level facet value. This will be addressed by
adding numbering to the EntityName of of .Self in a BindSymbolicName.
See the third model in
https://docs.google.com/document/d/1Yt-i5AmF76LSvD4TrWRIAE_92kii6j5yFiW-S7ahzlg/edit?tab=t.0
for the plan. For now, there is a TODO addressing this.
Make Subst perform "recursion" on the RHS instructions as they are
replaced, effectively doing a depth-first traversal through the rewrite
constraints doing replacements. This allows us to fully compute
individual associated constants in the minimal amount of work, and cache
the results so they can be reused cheaply in cases where the rewrite
constraints generate an exponential number of references to associated
constants.
Fixes https://github.com/carbon-language/carbon-lang/issues/5672
Change impls from `<interface>.impl` to `<self>.as.<interface>.impl`,
and *member* functions to `<parent scope>.<fn>` (non-member functions
exclude their parent scope). Stop special-casing builtin functions,
given the new naming scheme.
The purpose of this is to make it clearer when a member function is
being accessed and, if so, which member function. In particular, we
often access interface `Op` functions. The builtin function
special-casing was intended to help with that, but we still have lots of
`Op` functions. This particular approach should make the interactions
clearer.
This changes up queueing of block IDs a little because, in particular,
we need to process bodies of entities only after constants finish
processing. But, it should also result in less memory usage during
processing because it means we have less on the insts stack at any given
time, since we track a block rather than all instructions contained by
the block.
The none.carbon min-prelude is not just an empty prelude, it also
prevents any prelude from being imported at all. So no import machinery
runs before the test, only the `package` statement from the prelude
would run.
Use the none.carbon min-prelude in a few tests that were specifying
`--no-prelude-import` to give it a trial run.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Given a facet type: `(Z where .X = .Y) where .X =.Y`
The rewrite constraints in the inner facet type are each an
`ImplWitnessAccess` into a witness for the self of type `Z` (which is
the facet type before the `where`). The rewrite constraints in the outer
facet type are each an `ImplWitnessAccess` for the self of type `Z where
.X = .Y`, which is a different self facet type.
This means when deduping in canonicalization, the first `.X` and the
second `.X` are different instructions, and different constant values,
so they both remain in the rewrite constraints, incorrectly. Then if the
outer `.X` is allowed to evaluate to a value from its facet type, it
finds `.Y` resulting in `.Y = .Y` which is also incorrect.
Because of the failure to dedupe the first facet type, that is also
diagnosed as two different assignments to the same `.X`. To resolve
that, we introduce `CompareFacetTypeConstraintValues()` compare values
in facet type constraints, and treat accesses to the same associated
constant in the same facet value as `equivalent` even when through
different witnesses. This allows us to dedupe the two `.X = .Y` rules
into one in the combined facet type.
Given a different facet type: `(Z where .X = ()) where .X = {}`. Here we
want to diagnose that `.X` has been assigned two different values. To do
so, we need to see that the two `.X` values are the same, and we use
`CompareFacetTypeConstraintValues()` to do this comparison. Then we see
two rewrite rules for the same LHS, and we can diagnose that.
We enable evaluating `ImplWitnessAccess` on `.Self` to pull a value from
rewrite constraints in a facet type so that we can see that we are not
incorrect evaluating the LHS of rewrite constraints and producing
cycles. By doing so, also enable generic code to see and use concrete
values in associated constants in facet types.
The `BitAnd` operation combines two `FacetTypeInfo` structures by
concatenating their lists, but did not apply the current specific to the
instructions in the `FacetTypeInfo` as it forgot to go through
`GetContantFacetTypeInfo`.
`WhereExpr` handling duplicates a lot of the logic in
`GetConstantFacetTypeInfo` by calling `GetConstantValue` on things,
instead of calling `GetConstantFacetTypeInfo` on the `FacetTypeInfo` it
constructs. This meant it also needed to call `GetConstantFacetTypeInfo`
on the base facet type, and on any `impls`-requirement facet types
before merging their values together into a single `FacetTypeInfo`.
Instead, make `WhereExpr` more like `BitAnd`, and have it concatenate
things together as-is to construct a `FacetTypeInfo`. Then call
`GetConstantFacetTypeInfo` to canonicalize it and return a constant
value referring to it.
In `GetConstantFacetTypeInfo` we fix a crasher by propagating errors
inserted into the `FacetTypeInfo` out to the `Phase` so that the
resulting instruction depending on the `FacetTypeInfo` is not resolved
to a constant value with errors inside it. A test is added for this,
which was crashing on import of the `FacetType` with an error within
from the imported `impl` decl.
This refactoring gives us three benefits:
* There's now only a single place that does
`ResolveRewriteConstraintsAndCanonicalize`, which is inside
`GetConstantFacetTypeInfo`. This makes the inputs/behaviour of
`ResolveRewriteConstraintsAndCanonicalize` more consistent.
* There's now only a single place that updates the instructions in
`FacetTypeInfo` constraints with new constant values, so that changes
that rely on observing and interacting with that code only need to be
written in a single place. This will avoid duplicating logic in
https://github.com/carbon-language/carbon-lang/pull/5644.
* This will make it easier to move `WhereExpr` handling to a
`EvalConstantInst` function, as it no longer directly depends on
`GetConstantValue()` from `eval.cpp`.
If the RHS of a rewrite constraint refers to an associated constant,
pull the value for that constant from other rewrite constraints. We
repeat this each time a RHS value is changed until we reach a fixed
point, as per the "Rewrite constraint resolution" rule:
https://docs.carbon-lang.dev/docs/design/generics/appendix-rewrite-constraints.html#rewrite-constraint-resolution
While replacing references to associated constants in the RHS, if the
reference is to the LHS of the same rewrite constraint, we diagnose it
as a cycle which has no fixed point, and replace reference to the
associated constant with `ErrorInst`.
Add a facet type rewrite constraint resolution step that is run every
time a facet type is constructed, in line with the design here:
https://docs.carbon-lang.dev/docs/design/generics/appendix-rewrite-constraints.html#rewrite-constraint-resolution
The resolution has multiple steps, and this PR implements the first of
them, finding and diagnosing any duplicate rewrites to the same
associated constant.
We already diagnosed this for impl construction, now we do so for all
facet types, which includes the one used for impl construction, so this
diagnostic is a superset of the previous.
People seemed receptive [on
#toolchain](https://discord.com/channels/655572317891461132/655578254970716160/1379196447827689553),
so proceeding.
For the two name conflicts, I've set it up so that there's a
"foo.carbon" and "foo_with_prelude.carbon", to indicate that the
no-prelude approach is preferred (with a shorter name).
Note min_prelude will require a little more work/thought, I want to
avoid adding `--custom-core` etc.
Where `--no-dump-sem-ir` is used, change to `--dump-sem-ir-ranges=only`.
Otherwise, add `--dump-sem-ir-ranges=if-present` with a TODO to change
to `only`.
Note, SemIR is affected just because the extra comments change line
numbers in files where splits aren't in use.
Don't import `ImplWitnessTable` into the `constants` block, because we
generally don't put `Unique` constants there. This matches the handling
of the other kinds of `Unique` constants. In order to keep the
instruction visible in formatted SemIR, add it to the `imports` block
instead.
Also fix a bug in the instruction formatter that resulted in
instructions in the `imports` block being omitted from the output if
they were only referenced by earlier instructions in the `imports` block
and by instructions in the `constants` block. This was already resulting
in some referenced instructions being omitted from the output, but also
occurred frequently for `impl_witness_table` instructions after this
change because it is common for the only reference to those instructions
to be from `impl_witness` instructions in the `constants` block.
We eliminate the `FacetAccessWitness` instruction, which would sometimes
immediately evaluate to a concrete `ImplWitness`, and sometimes remain
symbolic. This instruction is now replaced by `LookupImplWitness` in all
cases. To support the same use cases, when it is evaluated,
`LookupImplWitness` will look in the self value if it's a facet value,
and attempt to return a concrete `ImplWitness` from it before looking
for an `impl` statement.
The `LookupImplWitness` instruction's value is now canonical, even when
it evaluates to a symbolic `LookupImplWitness` instruction, by
canonicalizing the self value of the lookup query. This canonicalization
unwraps `FacetAccessType` and `FacetValue` instructions to get to an
underlying canonical facet value. However we must preserve and use the
non-canonical query while evaluating the instruction in order to look
for a concrete `ImplWitness` if the query self value was a concrete
`FacetValue`. The canonicalization ensures that symbolic witnesses
obtained from a facet value are compatible with those obtained from an
impl statement, as long as the self types originate from the same
canonical facet value though they may have been narrowed.
Member access now unconditionally does a `LookupImplWitness()`
operation, instead of only sometimes doing the lookup for a final impl
declaration.
`EvalImplLookupResult` is marked `[[nodiscard]]` so that we don't
construct it and forget to return it. This was a mistake made at one
point during the creation of this PR. And the `has_concrete_value()`
method no longer has a precondition that `has_value()` is true, since we
want to look for a concrete result only in the new use of
`EvalImplLookupResult` returned from lookup into the query self facet
value.
The TODO from `FacetAccessWitness` evaluation is addressed by ensuring
the index of the witness in the `FacetValue` comes from the required
interfaces of the `FacetValue`'s type, and that the type (a `FacetType`)
is the same facet type used in the query to construct the `FacetValue`'s
witness block. This is made possible by eliminating the
`FacetAccessWitness` indirection. The lookup into a `FacetValue` happens
while evaluating `LookupImplWitness` and it does so directly on the self
value. This gives a consistent view of the witness set and the facet
type, as they both come from the same instruction.
All of this with 400 less lines of code. :)
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Provide builtins for compound assignments instead of defining them in
the prelude as a use of a binary operator and an assignment. This allows
us to lower compound assignment directly to LLVM operations instead of
producing a function call. In the short term this also allows us to
define a type-generic compound assignment in the prelude.
This allows us to import the table for a given impl only once, while we
can import many ImplWitness instructions with different specifics for a
generic impl.
For example in convert_facet_value_to_narrowed_facet_type.carbon we see
that a single witness table is imported for the BitAnd interface, with
multiple witnesses (for different specifics) imported and sharing the
same table.
The ImplWitnessTable now contains a back-link to the Impl the witness is
for, allowing inst namer to name that interface in the textual semir,
and allowing the interface to be found when debugging from a witness.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Use it to stringify associated constant values in diagnostics. In
passing, add missing support for stringifying bool literals. Note that
there are some cases that it doesn't stringify properly, but that's not
new here; such cases could already be observed when stringifying generic
arguments.
Richard Smith
Dana JansensandRichard Smith
Geoff Romer
Elliott Kalt
