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Introduce Diagnostics::ContextScope and remove diagnoser callbacks in type completion (#6761)

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Introduces `Context` and `SoftContext` messages, which can be introduced
through a `ContextBuilder`:
- The `Context` messages come before the diagnostic in the output.
- The first `Context` message steals the diagnostic level from the main
diagnostic, and turns the main diagnostic into a Note attached to the
context.
- A `SoftContext` message works similarly, but if it's preceeded by a
`Context` or `SoftContext` message, then it is dropped. This can be used
as a default/backup scope when nothing more interesting is provided up
the stack, such as in `TryEvalBlockForSpecific`.

The `ContextBuilder` is provided to a callback through
`Diagnostics::ContextScope`, an RAII type `AnnotationScope` but for
context messages.

This allows a high level operation to provide a context message like
"failed to identify facet type {0}" which will then be used as the error
if a diagnostic is produced during identification, with the latter
diagnostic attached as a note to explain why the contextual operation
failed.

In particular, this allows monomorphization errors (such as an array
bound being negative) to be attached to a higher lever operation instead
of being top-level diagnostics themselves, with the monomorphization
site being a note. This inverts the source code locations that appear in
the diagnostic, so that the top-level diagnostic points to the "user
code" which causes the monomorphization.

This is presented as an alternative strategy to #6753, which plumbed
diagnoser callbacks around to achieve the same goals.

We replace the diagnoser callbacks in type completion and operators with
ContextScope callbacks instead, which now provide better diagnostics for
monomorphization errors. Other callers to MakeSpecific do not yet have
ContextScopes introduced in order to turn monomorphization errors into
more interesting diagnostics.
This commit is contained in:
Dana Jansens
2026-02-25 15:15:29 +00:00
committed by GitHub
parent e2bdbe8507
commit fbc8d59d32
139 changed files with 1349 additions and 1172 deletions
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toolchain/check/handle_binding_pattern.cpp
+35 -31
View File
@@ -163,13 +163,12 @@ static auto HandleAnyBindingPattern(Context& context, Parse::NodeId node_id,
return binding.pattern_id;
};
auto abstract_diagnoser = [&] {
CARBON_DIAGNOSTIC(AbstractTypeInVarPattern, Error,
auto abstract_diagnostic_context = [&](auto& builder) {
CARBON_DIAGNOSTIC(AbstractTypeInVarPattern, Context,
"binding pattern has abstract type {0} in `var` "
"pattern",
SemIR::TypeId);
return context.emitter().Build(type_node, AbstractTypeInVarPattern,
cast_type_id);
builder.Context(type_node, AbstractTypeInVarPattern, cast_type_id);
};
// A `self` binding can only appear in an implicit parameter list.
@@ -219,11 +218,10 @@ static auto HandleAnyBindingPattern(Context& context, Parse::NodeId node_id,
auto& class_info = context.classes().Get(class_type.class_id);
if (class_info.inheritance_kind ==
SemIR::Class::InheritanceKind::Abstract) {
auto builder = abstract_diagnoser();
auto direct_use = true;
NoteAbstractClass(context, class_type.class_id, direct_use,
builder);
builder.Emit();
Diagnostics::ContextScope scope(&context.emitter(),
abstract_diagnostic_context);
DiagnoseAbstractClass(context, class_type.class_id,
/*direct_use=*/true);
cast_type_id = SemIR::ErrorInst::TypeId;
}
}
@@ -256,21 +254,27 @@ static auto HandleAnyBindingPattern(Context& context, Parse::NodeId node_id,
}
case FullPatternStack::Kind::NameBindingDecl: {
auto incomplete_diagnoser = [&] {
CARBON_DIAGNOSTIC(IncompleteTypeInBindingDecl, Error,
auto incomplete_diagnostic_context = [&](auto& builder) {
CARBON_DIAGNOSTIC(IncompleteTypeInBindingDecl, Context,
"binding pattern has incomplete type {0} in name "
"binding declaration",
InstIdAsType);
return context.emitter().Build(type_node, IncompleteTypeInBindingDecl,
cast_type_inst_id);
builder.Context(type_node, IncompleteTypeInBindingDecl,
cast_type_inst_id);
};
if (node_kind == Parse::NodeKind::VarBindingPattern) {
cast_type_id = AsConcreteType(context, cast_type_id, type_node,
incomplete_diagnoser, abstract_diagnoser);
if (!RequireConcreteType(context, cast_type_id, type_node,
incomplete_diagnostic_context,
abstract_diagnostic_context)) {
cast_type_id = SemIR::ErrorInst::TypeId;
}
} else {
cast_type_id = AsCompleteType(context, cast_type_id, type_node,
incomplete_diagnoser);
if (!RequireCompleteType(context, cast_type_id, type_node,
incomplete_diagnostic_context)) {
cast_type_id = SemIR::ErrorInst::TypeId;
}
}
auto binding_pattern_id = make_binding_pattern();
if (node_kind == Parse::NodeKind::VarBindingPattern) {
CARBON_CHECK(!is_generic);
@@ -404,20 +408,20 @@ auto HandleParseNode(Context& context, Parse::FieldNameAndTypeId node_id)
auto parent_class_decl =
context.scope_stack().TryGetCurrentScopeAs<SemIR::ClassDecl>();
CARBON_CHECK(parent_class_decl);
cast_type_id = AsConcreteType(
context, cast_type_id, type_node,
[&] {
CARBON_DIAGNOSTIC(IncompleteTypeInFieldDecl, Error,
"field has incomplete type {0}", SemIR::TypeId);
return context.emitter().Build(type_node, IncompleteTypeInFieldDecl,
cast_type_id);
},
[&] {
CARBON_DIAGNOSTIC(AbstractTypeInFieldDecl, Error,
"field has abstract type {0}", SemIR::TypeId);
return context.emitter().Build(type_node, AbstractTypeInFieldDecl,
cast_type_id);
});
if (!RequireConcreteType(
context, cast_type_id, type_node,
[&](auto& builder) {
CARBON_DIAGNOSTIC(IncompleteTypeInFieldDecl, Context,
"field has incomplete type {0}", SemIR::TypeId);
builder.Context(type_node, IncompleteTypeInFieldDecl, cast_type_id);
},
[&](auto& builder) {
CARBON_DIAGNOSTIC(AbstractTypeInFieldDecl, Context,
"field has abstract type {0}", SemIR::TypeId);
builder.Context(type_node, AbstractTypeInFieldDecl, cast_type_id);
})) {
cast_type_id = SemIR::ErrorInst::TypeId;
}
if (cast_type_id == SemIR::ErrorInst::TypeId) {
cast_type_inst_id = SemIR::ErrorInst::TypeInstId;
}