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https://github.com/carbon-language/carbon-lang.git
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Dana Jansens
835a61c385
While this can only happen when some other error is taking place, we should handle it gracefully and report a concrete (but unmatchable) value in the type structure instead of CHECK-failing.
84 lines
3.3 KiB
Plaintext
84 lines
3.3 KiB
Plaintext
// 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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//
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// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/none.carbon
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//
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// AUTOUPDATE
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// TIP: To test this file alone, run:
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// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/impl/lookup/access.carbon
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// TIP: To dump output, run:
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// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/impl/lookup/access.carbon
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// --- impl_witness_access_in_impl_type_structure.carbon
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library "[[@TEST_NAME]]";
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interface X(T:! type) {}
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interface Y {
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let Y1:! type;
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}
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interface Z {
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let Z1:! type;
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}
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// There's 2 ImplWitnessAccess instructions in the type, but they together
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// resolve to a symbolic type value, so the type structure is: `? as X(?)`
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impl forall [T:! Z where .Z1 impls Y] T as X(T.Z1.(Y.Y1)) {}
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class C {
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impl as Y where .Y1 = {} {}
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}
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fn F(V:! Z where .Z1 = C) {
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// The type stucture is `? as X({})` which will match the impl's less specific
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// `? as X(?)`, then the impl will deduce the parameter of `X` to be `{}` from
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// the type of `V`. This would fail if ImplWitnessAccess instructions were
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// treated as Concrete in the type structure, since the impl would have a
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// different concrete value (an ImplWitnessAccess) than the query (a
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// StructValue).
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V as X({});
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}
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fn G(V:! Z where .Z1 impls Y) {
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// The type structure is `? as X(?)`, also built from ImplWitnessAccess insts,
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// which will match the impl's `? as X(?)`.
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V as X(V.(Z.Z1).(Y.Y1));
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}
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fn H(U:! type, V:! Z where .Z1 impls (Y where .Y1 = U)) {
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// The type structure is `? as X(?)`, without using an ImplWitnessAccess,
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// which will match the impl's `? as X(?)`. This would fail if
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// ImplWitnessAccess instructions were treated as Concrete in the type
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// structure, since the impl's type structure would be more specific than the
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// query's.
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V as X(U);
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}
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// --- fail_concrete_impl_witness_access_in_type_structure.carbon
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library "[[@TEST_NAME]]";
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interface Z(T:! type) {
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let Z1:! type;
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}
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interface Y {}
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class C;
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// Converting to this facet type requires a lookup for `C.(Z(C).Z1) as Y`. That
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// has a type structure that contains a fully concrete ImplWitnessAccess. But if
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// the lookup fails because there is no impl for `C as Z(C)`, then the access
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// remains in the type structure as is. This test ensures the type structure can
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// handle this edge case.
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fn F(unused T:! Z(.Self) where C impls (Z(C) where .Z1 impls Y)) {}
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fn G(T:! Z(.Self)) {
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// CHECK:STDERR: fail_concrete_impl_witness_access_in_type_structure.carbon:[[@LINE+7]]:3: error: cannot convert type `T` that implements `Z(.Self)` into type implementing `Z(.Self) where C impls Z(C) and C.(Z(C).Z1) impls Y` [ConversionFailureFacetToFacet]
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// CHECK:STDERR: F(T);
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// CHECK:STDERR: ^~~~
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// CHECK:STDERR: fail_concrete_impl_witness_access_in_type_structure.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
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// CHECK:STDERR: fn F(unused T:! Z(.Self) where C impls (Z(C) where .Z1 impls Y)) {}
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// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// CHECK:STDERR:
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F(T);
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}
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