[ASTScope] Customize getClassName() for GenericTypeOrExtensionScope

The subclasses of `GenericTypeOrExtensionScope` are customized by a `Portion`
mix-in class that effectively makes each into several different scope
nodes: one for the "whole decl", one for the where clause, one for the
body. Re-introduce the customized `getClassName()` operation so we get
the nicer debugging dumps.

Author: DougGregor

include/swift/AST/ASTScope.h

@@ -246,7 +246,7 @@ class ASTScopeImpl : public ASTAllocated<ASTScopeImpl> {
 
 public:
   const SourceFile *getSourceFile() const;
-  StringRef getClassName() const;
+  std::string getClassName() const;
 
   /// Print out this scope for debugging/reporting purposes.
   void print(llvm::raw_ostream &out, unsigned level = 0, bool lastChild = false,
@@ -609,6 +609,8 @@ class GenericTypeOrExtensionScope : public ASTScopeImpl {
   virtual bool doesDeclHaveABody() const;
   const char *portionName() const { return portion->portionName; }
 
+  std::string getClassName() const;
+
 public:
   // Only for DeclScope, not BodyScope
   // Returns the where clause scope, or the parent if none
@@ -630,6 +632,13 @@ class GenericTypeOrExtensionScope : public ASTScopeImpl {
 public:
   NullablePtr<const ASTScopeImpl> getLookupLimit() const override;
   virtual NullablePtr<const ASTScopeImpl> getLookupLimitForDecl() const;
+
+  static bool classof(const ASTScopeImpl *scope) {
+    return scope->getKind() == ScopeKind::NominalType ||
+           scope->getKind() == ScopeKind::Extension ||
+           scope->getKind() == ScopeKind::TypeAlias ||
+           scope->getKind() == ScopeKind::OpaqueType;
+  }
 };
 
 class GenericTypeScope : public GenericTypeOrExtensionScope {
@@ -656,6 +665,11 @@ class IterableTypeScope : public GenericTypeScope {
 
 public:
   NullablePtr<ASTScopeImpl> insertionPointForDeferredExpansion() override;
+
+  static bool classof(const ASTScopeImpl *scope) {
+    return scope->getKind() == ScopeKind::NominalType ||
+        scope->getKind() == ScopeKind::Extension;
+  }
 };
 
 class NominalTypeScope final : public IterableTypeScope {

lib/AST/ASTScope.cpp

@@ -160,13 +160,22 @@ DoCatchStmtScope::getCatchNodeBody() const {
   return { const_cast<DoCatchStmt *>(stmt), body };
 }
 
-StringRef ASTScopeImpl::getClassName() const {
+std::string ASTScopeImpl::getClassName() const {
+  // GenericTypeOrExtensionScope provides a custom implementation that deals
+  // with declaration names and "portions".
+  if (auto generic = dyn_cast<GenericTypeOrExtensionScope>(this))
+    return generic->getClassName();
+
   switch (getKind()) {
-#define SCOPE_NODE(Name) case ScopeKind::Name: return #Name;
+#define SCOPE_NODE(Name) case ScopeKind::Name: return #Name "Scope";
 #include "swift/AST/ASTScopeNodes.def"
   }
 }
 
+std::string GenericTypeOrExtensionScope::getClassName() const {
+  return declKindName() + portionName() + "Scope";
+}
+
 NullablePtr<Decl> ASTScopeImpl::getDeclIfAny() const {
   switch (getKind()) {
     // Declaration scope nodes extract the decl directly.