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When using the name of a template variable or concept in places
where an expression was expected, Clang would drop the cxxscope token
preceeding it, if any.
This leads to subpar diagnostics - complaining about the
identifier being undeclared as clang would not know to look into a
non-global scope.
We make sure the scope is preserved.
When encountering `ns::Concept foo x;`, Clang would also fail
to provide the same quality as it does at global scope.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D146719
Files:
clang/lib/Parse/ParseDecl.cpp
clang/lib/Parse/Parser.cpp
clang/test/Parser/cxx-template-template-recovery.cpp
Index: clang/test/Parser/cxx-template-template-recovery.cpp
===================================================================
--- /dev/null
+++ clang/test/Parser/cxx-template-template-recovery.cpp
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -std=c++20 -verify -fsyntax-only %s
+
+namespace a {
+ template <typename T>
+ concept C1 = true; //expected-note {{here}}
+
+ template <typename T>
+ auto V1 = true; //expected-note {{here}}
+
+ namespace b {
+ template <typename T>
+ concept C2 = true; //expected-note {{here}}
+
+ template <typename T>
+ auto V2 = true; //expected-note {{here}}
+ }
+}
+
+template <typename T>
+concept C3 = true; //expected-note {{here}}
+template <typename T>
+auto V3 = true; //expected-note {{here}}
+
+template <template <typename T> typename C>
+constexpr bool test = true;
+
+static_assert(test<a::C1>); //expected-error {{too few template arguments for concept 'C1'}}
+static_assert(test<a::b::C2>); //expected-error {{too few template arguments for concept 'C2'}}
+static_assert(test<C3>); //expected-error {{too few template arguments for concept 'C3'}}
+
+static_assert(test<a::V1>); //expected-error {{use of variable template 'V1' requires template arguments}}
+static_assert(test<a::b::V2>); //expected-error {{use of variable template 'V2' requires template arguments}}
+static_assert(test<V3>); //expected-error {{use of variable template 'V3' requires template arguments}}
+
+
+void f() {
+ C3 t1 = 0; // expected-error{{expected 'auto' or 'decltype(auto)' after concept name}}
+ a::C1 t2 = 0; // expected-error{{expected 'auto' or 'decltype(auto)' after concept name}}
+ a::b::C2 t3 = 0; // expected-error{{expected 'auto' or 'decltype(auto)' after concept name}}
+}
Index: clang/lib/Parse/Parser.cpp
===================================================================
--- clang/lib/Parse/Parser.cpp
+++ clang/lib/Parse/Parser.cpp
@@ -1883,31 +1883,25 @@
return ANK_TemplateName;
}
[[fallthrough]];
+ case Sema::NC_Concept:
case Sema::NC_VarTemplate:
case Sema::NC_FunctionTemplate:
case Sema::NC_UndeclaredTemplate: {
- // We have a type, variable or function template followed by '<'.
- ConsumeToken();
- UnqualifiedId Id;
- Id.setIdentifier(Name, NameLoc);
- if (AnnotateTemplateIdToken(
- TemplateTy::make(Classification.getTemplateName()),
- Classification.getTemplateNameKind(), SS, SourceLocation(), Id))
- return ANK_Error;
- return ANK_Success;
- }
- case Sema::NC_Concept: {
- UnqualifiedId Id;
- Id.setIdentifier(Name, NameLoc);
+ bool IsConceptName = Classification.getKind() == Sema::NC_Concept;
+ // We have a template name followed by '<'. Consume the identifier token so
+ // we reach the '<' and annotate it.
if (Next.is(tok::less))
- // We have a concept name followed by '<'. Consume the identifier token so
- // we reach the '<' and annotate it.
ConsumeToken();
+ UnqualifiedId Id;
+ Id.setIdentifier(Name, NameLoc);
if (AnnotateTemplateIdToken(
TemplateTy::make(Classification.getTemplateName()),
Classification.getTemplateNameKind(), SS, SourceLocation(), Id,
- /*AllowTypeAnnotation=*/false, /*TypeConstraint=*/true))
+ /*AllowTypeAnnotation=*/!IsConceptName,
+ /*TypeConstraint=*/IsConceptName))
return ANK_Error;
+ if (SS.isNotEmpty())
+ AnnotateScopeToken(SS, !WasScopeAnnotation);
return ANK_Success;
}
}
Index: clang/lib/Parse/ParseDecl.cpp
===================================================================
--- clang/lib/Parse/ParseDecl.cpp
+++ clang/lib/Parse/ParseDecl.cpp
@@ -3448,12 +3448,12 @@
continue;
}
- if (TemplateId && TemplateId->Kind == TNK_Concept_template &&
- GetLookAheadToken(2).isOneOf(tok::kw_auto, tok::kw_decltype)) {
+ if (TemplateId && TemplateId->Kind == TNK_Concept_template) {
DS.getTypeSpecScope() = SS;
- // This is a qualified placeholder-specifier, e.g., ::C<int> auto ...
- // Consume the scope annotation and continue to consume the template-id
- // as a placeholder-specifier.
+ // This is probably a qualified placeholder-specifier, e.g., ::C<int>
+ // auto ... Consume the scope annotation and continue to consume the
+ // template-id as a placeholder-specifier. Let the next iteration
+ // diagnose a missing auto.
ConsumeAnnotationToken();
continue;
}
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