Teach the ASTSynthesis stuff how to add generic constraints

Author: rjmccall

include/swift/AST/ASTSynthesis.h

@@ -135,7 +135,7 @@ struct VariadicSynthesizerStorage<> {
   constexpr VariadicSynthesizerStorage() {}
 
   template <class Fn>
-  void visit(const Fn &fn) const {}
+  void visit(Fn &&fn) const {}
 };
 template <class Head, class... Tail>
 struct VariadicSynthesizerStorage<Head, Tail...> {
@@ -145,7 +145,7 @@ struct VariadicSynthesizerStorage<Head, Tail...> {
     : head(head), tail(tail...) {}
 
   template <class Fn>
-  void visit(const Fn &fn) const {
+  void visit(Fn &&fn) const {
     fn(head);
     tail.visit(fn);
   }

lib/AST/Builtins.cpp

@@ -162,6 +162,33 @@ namespace {
 /// for generics.
 enum UnrestrictedGenericParam { _unrestricted };
 
+/// A synthesizer which generates a conformance requirement.
+template <class TypeS, class ProtocolS>
+struct ConformsToSynthesizer {
+  TypeS Type;
+  ProtocolS Protocol;
+};
+template <class TypeS, class ProtocolS>
+constexpr ConformsToSynthesizer<TypeS, ProtocolS>
+_conformsTo(TypeS type, ProtocolS protocol) {
+  return {type, protocol};
+}
+
+/// A synthesizer which generates a layout constraint requirement.
+template <class TypeS>
+struct LayoutConstraintSynthesizer {
+  TypeS Type;
+  LayoutConstraint Constraint;
+};
+template <class TypeS>
+LayoutConstraintSynthesizer<TypeS>
+_layout(TypeS type, LayoutConstraint constraint) {
+  return {type, constraint};
+}
+static LayoutConstraint _classLayout() {
+  return LayoutConstraint::getLayoutConstraint(LayoutConstraintKind::Class);
+}
+
 /// A synthesizer which generates a generic parameter list.
 template <class... ParamS>
 struct GenericParamListSynthesizer {
@@ -179,6 +206,16 @@ struct CountGenericParameters {
   void operator()(UnrestrictedGenericParam _) const {
     Count++;
   }
+
+  template <class TypeS, class ProtoS>
+  void operator()(const ConformsToSynthesizer<TypeS, ProtoS> &_) const {
+    // not a parameter
+  }
+
+  template <class TypeS>
+  void operator()(const LayoutConstraintSynthesizer<TypeS> &_) const {
+    // not a parameter
+  }
 };
 
 } // end anonymous namespace
@@ -240,15 +277,30 @@ struct CollectGenericParams {
     }
   }
 
-  void operator()(UnrestrictedGenericParam _) const {}
+  void operator()(UnrestrictedGenericParam _) {}
+
+  template <class TypeS, class ProtoS>
+  void operator()(const ConformsToSynthesizer<TypeS, ProtoS> &conf) {
+    auto type = synthesizeType(SC, conf.Type);
+    auto protocolType = synthesizeType(SC, conf.Protocol);
+    AddedRequirements.push_back({RequirementKind::Conformance,
+                                 type, protocolType});
+  }
+
+  template <class TypeS>
+  void operator()(const LayoutConstraintSynthesizer<TypeS> &req) {
+    auto type = synthesizeType(SC, req.Type);
+    AddedRequirements.push_back({RequirementKind::Layout,
+                                 type, req.Constraint});
+  }
 };
 
 } // end anonymous namespace
 
 template <class... ParamsS>
 static GenericSignature
 synthesizeGenericSignature(SynthesisContext &SC,
-                           GenericParamListSynthesizer<ParamsS...> list) {
+                     const GenericParamListSynthesizer<ParamsS...> &list) {
   assert(SC.GenericParams && "synthesizeGenericParamList not called first");
   CollectGenericParams collector(SC);
   list.Params.visit(collector);