AST cloning mechanism (#2699)

This is intended to be used for template instantiation, but for now takes no stance as to what it's cloning.

This is tested by parsing and cloning all of our test files, and checking that the result of converting each AST to proto is the same as the result of cloning and then converting each AST to proto.

explorer/ast/declaration.cpp

@@ -4,6 +4,7 @@
 
 #include "explorer/ast/declaration.h"
 
+#include "explorer/ast/value.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/Casting.h"
 
@@ -152,8 +153,16 @@ void Declaration::PrintID(llvm::raw_ostream& out) const {
           out << "external ";
           break;
       }
-      out << "impl " << *impl_decl.impl_type() << " as "
-          << impl_decl.interface();
+      out << "impl ";
+      if (!impl_decl.deduced_parameters().empty()) {
+        out << "forall [";
+        llvm::ListSeparator sep;
+        for (auto* param : impl_decl.deduced_parameters()) {
+          out << sep << *param;
+        }
+        out << "] ";
+      }
+      out << *impl_decl.impl_type() << " as " << impl_decl.interface();
       break;
     }
     case DeclarationKind::MatchFirstDeclaration:
@@ -271,12 +280,6 @@ auto GetName(const Declaration& declaration)
   }
 }
 
-void GenericBinding::Print(llvm::raw_ostream& out) const {
-  out << name() << ":! " << type();
-}
-
-void GenericBinding::PrintID(llvm::raw_ostream& out) const { out << name(); }
-
 void ReturnTerm::Print(llvm::raw_ostream& out) const {
   switch (kind_) {
     case ReturnKind::Omitted:
@@ -405,6 +408,27 @@ void CallableDeclaration::PrintDepth(int depth, llvm::raw_ostream& out) const {
   }
 }
 
+ClassDeclaration::ClassDeclaration(CloneContext& context,
+                                   const ClassDeclaration& other)
+    : Declaration(context, other),
+      name_(other.name_),
+      extensibility_(other.extensibility_),
+      self_decl_(context.Clone(other.self_decl_)),
+      type_params_(context.Clone(other.type_params_)),
+      base_expr_(context.Clone(other.base_expr_)),
+      members_(context.Clone(other.members_)),
+      base_type_(context.Clone(other.base_type_)) {}
+
+ConstraintTypeDeclaration::ConstraintTypeDeclaration(
+    CloneContext& context, const ConstraintTypeDeclaration& other)
+    : Declaration(context, other),
+      name_(other.name_),
+      params_(context.Clone(other.params_)),
+      self_type_(context.Clone(other.self_type_)),
+      self_(context.Clone(other.self_)),
+      members_(context.Clone(other.members_)),
+      constraint_type_(context.Clone(other.constraint_type_)) {}
+
 auto ImplDeclaration::Create(Nonnull<Arena*> arena, SourceLocation source_loc,
                              ImplKind kind, Nonnull<Expression*> impl_type,
                              Nonnull<Expression*> interface,
@@ -428,6 +452,19 @@ auto ImplDeclaration::Create(Nonnull<Arena*> arena, SourceLocation source_loc,
                                      interface, resolved_params, members);
 }
 
+ImplDeclaration::ImplDeclaration(CloneContext& context,
+                                 const ImplDeclaration& other)
+    : Declaration(context, other),
+      kind_(other.kind_),
+      deduced_parameters_(context.Clone(other.deduced_parameters_)),
+      impl_type_(context.Clone(other.impl_type_)),
+      self_decl_(context.Clone(other.self_decl_)),
+      interface_(context.Clone(other.interface_)),
+      constraint_type_(context.Clone(other.constraint_type_)),
+      members_(context.Clone(other.members_)),
+      impl_bindings_(context.Remap(other.impl_bindings_)),
+      match_first_(context.Remap(other.match_first_)) {}
+
 void AlternativeSignature::Print(llvm::raw_ostream& out) const {
   out << "alt " << name();
   if (auto params = parameters()) {
@@ -449,4 +486,10 @@ auto ChoiceDeclaration::FindAlternative(std::string_view name) const
   return std::nullopt;
 }
 
+MixDeclaration::MixDeclaration(CloneContext& context,
+                               const MixDeclaration& other)
+    : Declaration(context, other),
+      mixin_(context.Clone(other.mixin_)),
+      mixin_value_(context.Clone(other.mixin_value_)) {}
+
 }  // namespace Carbon