================
@@ -6484,6 +6499,57 @@ class SubstTemplateTypeParmType final
}
};
+/// Represents the result of substituting a set of types as a template argument
+/// that needs to be expanded later.
+///
+/// These types are always dependent and produced depending on the situations:
+/// - SubstTemplateTypeParmPack represents a pack expansion that had to be
+/// delayed,
+/// - TODO: represents a pack expansion represented by a builtin.
+class SubstPackType : public Type, public llvm::FoldingSetNode {
+ friend class ASTContext;
+
+ /// A pointer to the set of template arguments that this
+ /// parameter pack is instantiated with.
+ const TemplateArgument *Arguments;
+
+protected:
+ SubstPackType(TypeClass Derived, QualType Canon,
+ const TemplateArgument &ArgPack);
+
+public:
+ unsigned getNumArgs() const { return SubstPackTypeBits.NumArgs; }
+
+ TemplateArgument getArgumentPack() const;
+
+ void Profile(llvm::FoldingSetNodeID &ID);
+ static void Profile(llvm::FoldingSetNodeID &ID,
+ const TemplateArgument &ArgPack);
+
+ static bool classof(const Type *T) {
+ return T->getTypeClass() == SubstTemplateTypeParmPack ||
+ T->getTypeClass() == SubstBuiltinTemplatePack;
+ }
+};
+
+/// Represents the result of substituting a builtin template as a pack.
+class SubstBuiltinTemplatePackType : public SubstPackType {
+ friend class ASTContext;
+
+ SubstBuiltinTemplatePackType(QualType Canon, const TemplateArgument
&ArgPack);
----------------
zyn0217 wrote:
Can you explain what is preventing us from reusing
`SubstTemplateTypeParmPackType`?
The commit message said they are similar, but didn't explain why.
One possible reason I can think of is that, `collectUnexpandedParameterPacks`
doesn't like `SubstTemplateTypeParmPackType` node because some clients don't
expect it (e.g. in type deduction). But that can always be distincted (inside
the collector) by adding more flags to the type.
Treating that node as an unexpanded pack would also benefit our diagnostics,
see #121044
https://github.com/llvm/llvm-project/pull/106730
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