[AST] Introduce DeclContext::mapType(Into|OutOf)Context()

Use them to eliminate some more instances of getSelfTypeInContext().

Author: DougGregor

include/swift/AST/DeclContext.h

@@ -320,7 +320,13 @@ class alignas(1 << DeclContextAlignInBits) DeclContext {
   /// \brief Retrieve the innermost archetypes of this context or any
   /// of its parents.
   GenericEnvironment *getGenericEnvironmentOfContext() const;
-  
+
+  /// Map an interface type to a contextual type within this context.
+  Type mapTypeIntoContext(Type type) const;
+
+  /// Map a type within this context to an interface type.
+  Type mapTypeOutOfContext(Type type) const;
+
   /// Returns this or the first local parent context, or nullptr if it is not
   /// contained in one.
   DeclContext *getLocalContext();

lib/AST/DeclContext.cpp

@@ -301,6 +301,20 @@ GenericEnvironment *DeclContext::getGenericEnvironmentOfContext() const {
   }
 }
 
+Type DeclContext::mapTypeIntoContext(Type type) const {
+  if (auto genericEnv = getGenericEnvironmentOfContext())
+    return genericEnv->mapTypeIntoContext(getParentModule(), type);
+
+  return type;
+}
+
+Type DeclContext::mapTypeOutOfContext(Type type) const {
+  if (auto genericEnv = getGenericEnvironmentOfContext())
+    return genericEnv->mapTypeOutOfContext(getParentModule(), type);
+
+  return type;
+}
+
 DeclContext *DeclContext::getLocalContext() {
   if (isLocalContext())
     return this;

lib/Sema/CodeSynthesis.cpp

@@ -1789,8 +1789,8 @@ void swift::maybeAddAccessorsToVariable(VarDecl *var, TypeChecker &TC) {
       Type behaviorSelf;
       Type behaviorInterfaceSelf;
       if (dc->isTypeContext()) {
-        behaviorSelf = dc->getSelfTypeInContext();
         behaviorInterfaceSelf = dc->getSelfInterfaceType();
+        behaviorSelf = dc->mapTypeIntoContext(behaviorInterfaceSelf);
         assert(behaviorSelf && "type context doesn't have self type?!");
         if (var->isStatic())
           behaviorSelf = MetatypeType::get(behaviorSelf);

tools/SourceKit/lib/SwiftLang/SwiftSourceDocInfo.cpp

@@ -1260,8 +1260,10 @@ resolveCursorFromUSR(SwiftLangSupport &Lang, StringRef InputFile, StringRef USR,
       } else if (auto *VD = dyn_cast<ValueDecl>(D)) {
         auto *DC = VD->getDeclContext();
         Type selfTy;
-        if (DC->isTypeContext())
-          selfTy = DC->getSelfTypeInContext();
+        if (DC->isTypeContext()) {
+          selfTy = DC->getSelfInterfaceType();
+          selfTy = VD->getInnermostDeclContext()->mapTypeIntoContext(selfTy);
+        }
         bool Failed =
             passCursorInfoForDecl(VD, MainModule, selfTy, Type(),
                                   /*isRef=*/false, BufferID, Lang, CompInvok,