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Add tests of .Self given for an interface parameter that has constraints (#6181)

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This tests that `.Self` in an interface generic parameter preserves the
facet type information of the binding when returned, and allows compound
member lookup back into that interface.

And add a failing-todo test that `.Self` gets implied constraints which
can be satisfied through `&` for the facet type `I(.Self)` is part of.
This commit is contained in:
Dana Jansens
2025-10-08 16:51:23 +00:00
committed by GitHub
parent bfc4d2b127
commit fd74e49fd2
1 changed files with 36 additions and 0 deletions
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toolchain/check/testdata/facet/period_self.carbon
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@@ -313,6 +313,42 @@ interface I(T:! Core.Destroy) {}
// The `.Self` can see the LHS of the `where` to know `U` impls Core.Destroy.
fn F(U:! Core.Destroy where .Self impls I(.Self)) {}
// --- fail_todo_period_self_parameter_constraint_satisfied_with_type_and.carbon
library "[[@TEST_NAME]]";
interface I(T:! Core.Destroy) {}
// TODO: Implied constraints that `.Self` impls `Core.Destroy` are satisfied by
// the `&` expression.
//
// CHECK:STDERR: fail_todo_period_self_parameter_constraint_satisfied_with_type_and.carbon:[[@LINE+7]]:25: error: cannot convert type `.Self` that implements `type` into type implementing `Core.Destroy` [ConversionFailureFacetToFacet]
// CHECK:STDERR: fn F(U:! Core.Destroy & I(.Self)) {}
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR: fail_todo_period_self_parameter_constraint_satisfied_with_type_and.carbon:[[@LINE-8]]:13: note: initializing generic parameter `T` declared here [InitializingGenericParam]
// CHECK:STDERR: interface I(T:! Core.Destroy) {}
// CHECK:STDERR: ^
// CHECK:STDERR:
fn F(U:! Core.Destroy & I(.Self)) {}
// --- fail_todo_compound_lookup_on_returned_period_self_parameter.carbon
library "[[@TEST_NAME]]";
interface I(T:! Core.Destroy) {
fn G[self: Self]() -> T;
}
fn F[U:! Core.Destroy where .Self impls I(.Self)](u: U) {
// This tests that both `I.G` is accessible and that `Destroy` is preserved;
// we'd get an error for missing Destroy otherwise since G() returns an
// initializing expression.
// CHECK:STDERR: fail_todo_compound_lookup_on_returned_period_self_parameter.carbon:[[@LINE+4]]:3: error: cannot access member of interface `I(U as Core.Destroy)` in type `U` that does not implement that interface [MissingImplInMemberAccess]
// CHECK:STDERR: u.(I(U).G)().(I(U).G)().(I(U).G)();
// CHECK:STDERR: ^~~~~~~~~~
// CHECK:STDERR:
u.(I(U).G)().(I(U).G)().(I(U).G)();
}
// CHECK:STDOUT: --- period_self_param.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {