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https://github.com/carbon-language/carbon-lang.git
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Richard Smith
374bf9f853
Per recent discussion, in `... where .A = B`, require that `B` is implicitly convertible to the type of `A` immediately, rather than treating that as part of the criteria that a type must satisfy to satisfy the resulting constraint. Extend the implementation of implicit conversion so that conversion of a type to a constraint checks that the type satisfies the constraint. As part of implementing this, stop duplicating rewrite constraints as equality constraints. Instead, when checking that a constraint is satisfied, check both its equality constraints and its rewrite constraints. This fixes an infinite recursion that would otherwise be caused by this change, and is also a necessary prerequisite for applying rewrite constraints to equality constraints, where we would otherwise collapse the implied equality constraints to a tautological `V == V` constraint. In passing, make ErrorBuilder support building the error message more incrementally and use that to improve diagnostics for mismatched values with equality constraints.
34 lines
990 B
Plaintext
34 lines
990 B
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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// AUTOUPDATE
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// RUN: %{not} %{explorer-run}
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// RUN: %{not} %{explorer-run-trace}
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package ExplorerTest api;
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interface X(T:! Type) {}
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interface Y(T:! Type) {
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let M:! X(T);
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}
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interface Z {
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// We reject this even though it is the responsibility of the `impl as Z` to
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// provide a type `N` such that `i32 is X(N)`. We might want to treat this as
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// an implied constraint and allow this in the future.
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// CHECK:STDERR: COMPILATION ERROR: {{.*}}/explorer/testdata/assoc_const/fail_implied_constraints.carbon:[[@LINE+1]]: could not find implementation of interface X(T = N) for i32
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let N:! Y(.Self) where .M = i32;
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}
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impl i32 as X(i32) {}
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impl i32 as Y(i32) where .M = i32 {}
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impl i32 as Z where .N = i32 {}
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fn F[A:! Z](a: A) -> A { return a; }
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fn Main() -> i32 {
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return F(0);
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}
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