Diagnose explicit Self in extend in the parse node handler (Refactor Impl construction 1/7)
#6465
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−61
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This was referenced Dec 5, 2025
zygoloid
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Dec 5, 2025
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Some thoughts but apart from the "existant" -> "existent" spelling fix, these can all be deferred -- I appreciate this is part of a big refactor and it might be easier to handle these comments at the end of that, if they still apply at all.
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| // --- fail_extend_require_with_nonexistant_type.carbon | ||
| library "[[@TEST_NAME]]"; | ||
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| interface Y {} | ||
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| interface Z { | ||
| // CHECK:STDERR: fail_extend_require_with_nonexistant_type.carbon:[[@LINE+4]]:18: error: name `nonexistant` not found [NameNotFound] | ||
| // CHECK:STDERR: extend require nonexistant impls Y; | ||
| // CHECK:STDERR: ^~~~~~~~~~~ | ||
| // CHECK:STDERR: | ||
| extend require nonexistant impls Y; | ||
| } | ||
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| // --- fail_extend_require_with_nonexistant_type_pointer.carbon | ||
| library "[[@TEST_NAME]]"; | ||
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| interface Y {} | ||
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| interface Z { | ||
| // CHECK:STDERR: fail_extend_require_with_nonexistant_type_pointer.carbon:[[@LINE+4]]:18: error: name `nonexistant` not found [NameNotFound] | ||
| // CHECK:STDERR: extend require nonexistant* impls Y; | ||
| // CHECK:STDERR: ^~~~~~~~~~~ | ||
| // CHECK:STDERR: | ||
| extend require nonexistant* impls Y; | ||
| } |
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Suggested change
| // --- fail_extend_require_with_nonexistant_type.carbon | |
| library "[[@TEST_NAME]]"; | |
| interface Y {} | |
| interface Z { | |
| // CHECK:STDERR: fail_extend_require_with_nonexistant_type.carbon:[[@LINE+4]]:18: error: name `nonexistant` not found [NameNotFound] | |
| // CHECK:STDERR: extend require nonexistant impls Y; | |
| // CHECK:STDERR: ^~~~~~~~~~~ | |
| // CHECK:STDERR: | |
| extend require nonexistant impls Y; | |
| } | |
| // --- fail_extend_require_with_nonexistant_type_pointer.carbon | |
| library "[[@TEST_NAME]]"; | |
| interface Y {} | |
| interface Z { | |
| // CHECK:STDERR: fail_extend_require_with_nonexistant_type_pointer.carbon:[[@LINE+4]]:18: error: name `nonexistant` not found [NameNotFound] | |
| // CHECK:STDERR: extend require nonexistant* impls Y; | |
| // CHECK:STDERR: ^~~~~~~~~~~ | |
| // CHECK:STDERR: | |
| extend require nonexistant* impls Y; | |
| } | |
| // --- fail_extend_require_with_nonexistent_type.carbon | |
| library "[[@TEST_NAME]]"; | |
| interface Y {} | |
| interface Z { | |
| // CHECK:STDERR: fail_extend_require_with_nonexistant_type.carbon:[[@LINE+4]]:18: error: name `nonexistent` not found [NameNotFound] | |
| // CHECK:STDERR: extend require nonexistent impls Y; | |
| // CHECK:STDERR: ^~~~~~~~~~~ | |
| // CHECK:STDERR: | |
| extend require nonexistent impls Y; | |
| } | |
| // --- fail_extend_require_with_nonexistent_type_pointer.carbon | |
| library "[[@TEST_NAME]]"; | |
| interface Y {} | |
| interface Z { | |
| // CHECK:STDERR: fail_extend_require_with_nonexistent_type_pointer.carbon:[[@LINE+4]]:18: error: name `nonexistent` not found [NameNotFound] | |
| // CHECK:STDERR: extend require nonexistent* impls Y; | |
| // CHECK:STDERR: ^~~~~~~~~~~ | |
| // CHECK:STDERR: | |
| extend require nonexistent* impls Y; | |
| } |
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| auto class_scope = | ||
| TryAsClassScope(context, context.decl_name_stack().PeekParentScopeId()); | ||
| if (class_scope) { |
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Suggested change
| auto class_scope = | |
| TryAsClassScope(context, context.decl_name_stack().PeekParentScopeId()); | |
| if (class_scope) { | |
| if (auto class_scope = | |
| TryAsClassScope(context, context.decl_name_stack().PeekParentScopeId())) { |
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| auto diag = context.emitter().Build(extend_node, ExtendImplSelfAs); | ||
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| if (self_type.type_id == GetImplDefaultSelfType(context, *class_scope)) { | ||
| // If the explicit self type is the default, suggest removing it with a | ||
| // diagnostic, but continue as if no error occurred since the self-type | ||
| // is semantically valid. | ||
| CARBON_DIAGNOSTIC(ExtendImplSelfAsDefault, Note, | ||
| "remove the explicit `Self` type here"); | ||
| diag.Note(self_node, ExtendImplSelfAsDefault); | ||
| if (self_type.type_id != SemIR::ErrorInst::TypeId) { | ||
| diag.Emit(); | ||
| } | ||
| } else if (self_type.type_id != SemIR::ErrorInst::TypeId) { | ||
| // Otherwise, the self-type is an error. | ||
| diag.Emit(); | ||
| class_scope->name_scope->set_has_error(); | ||
| self_type.inst_id = SemIR::ErrorInst::TypeInstId; | ||
| } | ||
| } |
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I think we should also call name_scope->set_has_error() if there's an error in the self type itself. So maybe:
Suggested change
| auto diag = context.emitter().Build(extend_node, ExtendImplSelfAs); | |
| if (self_type.type_id == GetImplDefaultSelfType(context, *class_scope)) { | |
| // If the explicit self type is the default, suggest removing it with a | |
| // diagnostic, but continue as if no error occurred since the self-type | |
| // is semantically valid. | |
| CARBON_DIAGNOSTIC(ExtendImplSelfAsDefault, Note, | |
| "remove the explicit `Self` type here"); | |
| diag.Note(self_node, ExtendImplSelfAsDefault); | |
| if (self_type.type_id != SemIR::ErrorInst::TypeId) { | |
| diag.Emit(); | |
| } | |
| } else if (self_type.type_id != SemIR::ErrorInst::TypeId) { | |
| // Otherwise, the self-type is an error. | |
| diag.Emit(); | |
| class_scope->name_scope->set_has_error(); | |
| self_type.inst_id = SemIR::ErrorInst::TypeInstId; | |
| } | |
| } | |
| auto diag = | |
| self_type.type_id == SemIR::ErrorInst::TypeId | |
| ? context.emitter().BuildSuppressed() | |
| : context.emitter().Build(extend_node, ExtendImplSelfAs); | |
| if (self_type.type_id == GetImplDefaultSelfType(context, *class_scope)) { | |
| // If the explicit self type is the default, suggest removing it with a | |
| // diagnostic, but continue as if no error occurred since the self-type | |
| // is semantically valid. | |
| CARBON_DIAGNOSTIC(ExtendImplSelfAsDefault, Note, | |
| "remove the explicit `Self` type here"); | |
| diag.Note(self_node, ExtendImplSelfAsDefault); | |
| } else { | |
| // Otherwise, the self-type is an error. | |
| class_scope->name_scope->set_has_error(); | |
| self_type.inst_id = SemIR::ErrorInst::TypeInstId; | |
| } | |
| } | |
| diag.Emit(); |
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| auto class_scope = | ||
| TryAsClassScope(context, context.decl_name_stack().PeekParentScopeId()); | ||
| if (class_scope) { |
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Suggested change
| auto class_scope = | |
| TryAsClassScope(context, context.decl_name_stack().PeekParentScopeId()); | |
| if (class_scope) { | |
| if (auto class_scope = | |
| TryAsClassScope(context, context.decl_name_stack().PeekParentScopeId())) { |
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| } | ||
| self_type.inst_id = SemIR::ErrorInst::TypeInstId; |
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Should we set the scope to be invalid here too?
| // TODO: If the explicit self-type matches a lookup of NameId::SelfType, | ||
| // add a note to the diagnostic: "remove the explicit `Self` type here", | ||
| // and continue without an ErrorInst. See ExtendImplSelfAsDefault. | ||
| context.emitter().Emit(self_node_id, RequireImplsExtendWithExplicitSelf); |
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It seems a bit inconsistent to be diagnosing this here but diagnosing the class case when handling the ImplTypeAs node.
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We encode the state of looking that the parent scope is a Class into a type so that we can avoid extra lookups. Then use that in refactoring where diagnostics are generated for an explicit
Selfin anextend impldeclaration.We add tests that we don't double-diagnose the Self type when it's already an error, and make the behaviour of
extend requirematch that ofextend impl as.This avoids some fragile/complex parse-node lookups (such as
context.parse_tree_and_subtrees().ExtractAs<Parse::ImplTypeAs>) by using the parse node at the point where we are handling it instead of much later.This is part of #6420 which is being split up into a chain of smaller PRs.