mirror of
https://github.com/carbon-language/carbon-lang.git
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Dana Jansens
77f1d93369
When replacing `.Self` in a facet type we don't want to destroy the structure of designators in rewrite constraints so that rewrite constraint resolution and other similar code can still find them. We were doing this only for the LHS, and for the RHS if it was a standalone designator, like `.X = .Y` but we want to do this more robustly to also avoid rewrite the `.Self` in `.Y` in the expression `.X = C(.Y)`. This allows resolution, and ImplWitnessAccess to recognize the designator and replace the `.Y` with the RHS value of another rewrite constraint assigning to `.Y`.
106 lines
4.9 KiB
C++
106 lines
4.9 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#ifndef CARBON_TOOLCHAIN_CHECK_PERIOD_SELF_H_
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#define CARBON_TOOLCHAIN_CHECK_PERIOD_SELF_H_
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#include "toolchain/check/context.h"
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#include "toolchain/check/subst.h"
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#include "toolchain/sem_ir/ids.h"
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namespace Carbon::Check {
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// Introduce `.Self` as a symbolic binding into the current scope, and return
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// the `SymbolicBinding` instruction.
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//
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// The type of `.Self` must be a `FacetType`, so that it gets wrapped in
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// `FacetAccessType` when used in a type position, such as in `U:! I(.Self)`.
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// This allows substitution with other facet values without requiring an
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// additional `FacetAccessType` to be inserted.
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auto MakePeriodSelfFacetValue(Context& context, SemIR::LocId loc_id,
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SemIR::TypeId self_type_id) -> SemIR::InstId;
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enum class SubstPeriodSelfBehaviour {
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ImplicitOnly,
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ExplicitOnly,
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All,
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};
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using SubstPeriodSelfRebuildInst =
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llvm::function_ref<auto(SemIR::Inst)->SemIR::InstId>;
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// Replace `.Self` references in `const_id` with `period_self_replacement_id`.
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//
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// The `behaviour` specifies if all `.Self` are replaced or just implicit use in
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// designators. The `rebuild` callback can optionally be specified to override
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// how an instruction is re-constructed to form an InstId after replacement. It
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// can return None to fall back to the default of evaluating the inst.
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auto SubstPeriodSelf(
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Context& context, SemIR::LocId loc_id, SemIR::ConstantId const_id,
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SemIR::ConstantId period_self_replacement_id,
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SubstPeriodSelfBehaviour behaviour = SubstPeriodSelfBehaviour::All,
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SubstPeriodSelfRebuildInst rebuild = nullptr) -> SemIR::ConstantId;
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// Replace `.Self` references in the specific of the interface or named
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// constraint with `period_self_replacement_id`.
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//
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// The `behaviour` specifies if all `.Self` are replaced or just implicit use in
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// designators. The `rebuild` callback can optionally be specified to override
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// how an instruction is re-constructed to form an InstId after replacement. It
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// can return None to fall back to the default of evaluating the inst.
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auto SubstPeriodSelf(
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Context& context, SemIR::LocId loc_id, SemIR::SpecificInterface interface,
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SemIR::ConstantId period_self_replacement_id,
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SubstPeriodSelfBehaviour behaviour = SubstPeriodSelfBehaviour::All,
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SubstPeriodSelfRebuildInst rebuild = nullptr) -> SemIR::SpecificInterface;
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auto SubstPeriodSelf(
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Context& context, SemIR::LocId loc_id,
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SemIR::SpecificNamedConstraint constraint,
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SemIR::ConstantId period_self_replacement_id,
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SubstPeriodSelfBehaviour behaviour = SubstPeriodSelfBehaviour::All,
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SubstPeriodSelfRebuildInst rebuild = nullptr)
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-> SemIR::SpecificNamedConstraint;
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// Replace `.Self` references with the self-type. The `facet_type_inst_id` must
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// be a `FacetType` instruction (or error).
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//
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// The implicit `.Self` in designators is not replaced in rewrite constraints,
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// to allow for rewrite constraint resolution to recognise the designators.
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// Later use of rewrite constraints requires further `.Self` replacement.
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//
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// Unlike SubstPeriodSelf, which works with constant values and thus canonical
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// instructions, this operation can be done for non-canonical facet types. A new
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// instruction is added for the output FacetType if anything does get replaced,
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// and the original instruction id is preserved otherwise.
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auto SubstPeriodSelfInFacetType(Context& context, SemIR::LocId loc_id,
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SemIR::TypeInstId self_type_inst_id,
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SemIR::TypeInstId facet_type_inst_id)
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-> SemIR::TypeInstId;
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// Returns whether the constant value of `inst_id` is a reference to `.Self`.
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//
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// If `canonicalize` is true, look at the constant value of `inst_id` and get
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// the canonicalized facet or type to look through FacetAccessType.
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auto IsPeriodSelf(Context& context, SemIR::InstId inst_id,
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bool canonicalize = true) -> bool;
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// Look for ambiguous `.Self` in a `T impls X where ...` statement. The given
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// inst ids are the non-canonical insts for the LHS and RHS of the `impls`
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// inside a `where` expression.
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//
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// If the LHS is not `.Self` and RHS contains a nested `where` expression, the
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// value of `.Self` becomes ambiguous on the RHS of the `where` (it could mean
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// either the original value or new value given by the LHS of the `impls`). Note
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// that implicit `.Self` references are never ambiguous, they always refer to
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// the innermost value that `.Self` could refer to.
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//
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// Returns true if an error was diagnosed.
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auto FindAndDiagnoseAmbiguousPeriodSelf(Context& context,
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SemIR::InstId impls_lhs_id,
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SemIR::InstId impls_rhs_id) -> bool;
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} // namespace Carbon::Check
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#endif // CARBON_TOOLCHAIN_CHECK_PERIOD_SELF_H_
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