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https://github.com/carbon-language/carbon-lang.git
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Dana Jansens
c74bb933d2
`LookupImplWitness` instructions inside the impl declaration can't use
the impl they are apart of. Previously we had an heuristic in eval which
would try to prevent finding the impl for a lookup from inside that
impl. But it breaks when the `.Self` is replaced in a generic impl with
a symbolic, and then that symbolic is replaced in a specific. The
specific's decl block contains that `LookupImplWitness` instruction and
it tries to use the impl it came from. This causes the same specific to
be formed again, but now it exists, so it's used as-is but it has no
decl block yet, and so we crash.
Now we ban an impl while we resolve its specific, both deduction of its
arguments and from any other substitution. The prevents instructions
from inside the impl (which are evaluated when resolving the specific)
from finding their own impl. We do so by adding the ImplId to a stack on
the Context, and then skipping such impls when looking for candidates
during eval.
This fixes a crash, which was demonstrated by the new test being added.
It also makes another todo test pass.
There's a whole lot of other semir churn, which seems to be mostly
reordering of constants. There are some fingerprint changes in
constants, but it appears they are the same canonical instructions, so
they don't represent a behaviour change. For example in
`toolchain/check/testdata/for/actual.carbon` the `%N.patt` constant has
been given its fingerprint suffix now as `%N.patt.aa5`. But they are
both this instruction, so it is just a formatting change:
```
inst6100001A: {kind: SymbolicBindingPattern, arg0: entity_name61000002, type: type(inst61000018)}
- name: `N`
- type: type(inst61000018): <pattern for Core.IntLiteral>; {kind: PatternType, arg0: inst(IntLiteralType), type: type(TypeType)} (concrete)
- value: symbolic_constant61000001
```
33 lines
1.3 KiB
C++
33 lines
1.3 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_DEDUCE_H_
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#define CARBON_TOOLCHAIN_CHECK_DEDUCE_H_
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#include "toolchain/check/context.h"
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#include "toolchain/sem_ir/ids.h"
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namespace Carbon::Check {
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// Deduces the generic arguments to use in a call to a generic.
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auto DeduceGenericCallArguments(Context& context, SemIR::LocId loc_id,
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SemIR::GenericId generic_id,
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SemIR::SpecificId enclosing_specific_id,
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SemIR::InstBlockId implicit_param_patterns_id,
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SemIR::InstBlockId param_patterns_id,
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SemIR::InstId self_id,
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llvm::ArrayRef<SemIR::InstId> arg_ids)
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-> SemIR::SpecificId;
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// Deduces the impl arguments to use in a use of a parameterized impl. Returns
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// `None` if deduction fails.
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auto DeduceImplArguments(Context& context, SemIR::LocId loc_id,
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SemIR::ImplId impl_id, SemIR::ConstantId self_id,
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SemIR::SpecificId constraint_specific_id)
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-> SemIR::SpecificId;
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} // namespace Carbon::Check
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#endif // CARBON_TOOLCHAIN_CHECK_DEDUCE_H_
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