AST: Add a way to distinguish a parsed generic parameter list from a synthesized one

Add a new GenericContext::getParsedGenericParams(). This produces
the same value as GenericContext::getGenericParams() if the generic
parameter list was written in source. For extensions and protocols,
this returns nullptr without synthesizing anything.

Author: slavapestov

include/swift/AST/Decl.h

@@ -1415,6 +1415,11 @@ class GenericContext : private _GenericContext, public DeclContext {
   /// this context is not generic.
   GenericParamList *getGenericParams() const;
 
+  /// Retrieve the generic parameters as written in source. Unlike
+  /// getGenericParams() this will not synthesize generic parameters for
+  /// extensions, protocols and certain type aliases.
+  GenericParamList *getParsedGenericParams() const;
+
   /// Determine whether this context has generic parameters
   /// of its own.
   ///

lib/AST/ASTDumper.cpp

@@ -561,7 +561,7 @@ namespace {
       };
 
       if (const auto GC = Owner.dyn_cast<const GenericContext *>()) {
-        if (!GC->isGeneric() || isa<ProtocolDecl>(GC))
+        if (GC->getParsedGenericParams() == nullptr)
           printWhere(GC->getTrailingWhereClause());
       } else {
         const auto ATD = Owner.get<const AssociatedTypeDecl *>();
@@ -730,9 +730,9 @@ namespace {
       OS << ' ';
       printDeclName(VD);
       if (auto *AFD = dyn_cast<AbstractFunctionDecl>(VD))
-        printGenericParameters(OS, AFD->getGenericParams());
+        printGenericParameters(OS, AFD->getParsedGenericParams());
       if (auto *GTD = dyn_cast<GenericTypeDecl>(VD))
-        printGenericParameters(OS, GTD->getGenericParams());
+        printGenericParameters(OS, GTD->getParsedGenericParams());
 
       if (auto *var = dyn_cast<VarDecl>(VD)) {
         PrintWithColorRAII(OS, TypeColor) << " type='";

lib/AST/ASTScopeCreation.cpp

@@ -1599,9 +1599,13 @@ ASTScopeImpl *GenericTypeOrExtensionWholePortion::expandScope(
   if (scope->shouldHaveABody() && !scope->doesDeclHaveABody())
     return ip;
 
+  auto *context = scope->getGenericContext();
+  auto *genericParams = (isa<TypeAliasDecl>(context)
+                         ? context->getParsedGenericParams()
+                         : context->getGenericParams());
   auto *deepestScope = scopeCreator.addNestedGenericParamScopesToTree(
-      scope->getDecl(), scope->getGenericContext()->getGenericParams(), scope);
-  if (scope->getGenericContext()->getTrailingWhereClause())
+      scope->getDecl(), genericParams, scope);
+  if (context->getTrailingWhereClause())
     scope->createTrailingWhereClauseScope(deepestScope, scopeCreator);
   scope->createBodyScope(deepestScope, scopeCreator);
   return ip;

lib/AST/ASTScopeLookup.cpp

@@ -292,7 +292,10 @@ NullablePtr<const GenericParamList> GenericTypeScope::genericParams() const {
   // Sigh... These must be here so that from body, we search generics before
   // members. But they also must be on the Decl scope for lookups starting from
   // generic parameters, where clauses, etc.
-  return getGenericContext()->getGenericParams();
+  auto *context = getGenericContext();
+  if (isa<TypeAliasDecl>(context))
+    return context->getParsedGenericParams();
+  return context->getGenericParams();
 }
 NullablePtr<const GenericParamList> ExtensionScope::genericParams() const {
   return decl->getGenericParams();

lib/AST/ASTWalker.cpp

@@ -129,7 +129,7 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
   bool visitGenericParamListIfNeeded(GenericContext *GC) {
     // Must check this first in case extensions have not been bound yet
     if (Walker.shouldWalkIntoGenericParams()) {
-      if (auto *params = GC->getGenericParams()) {
+      if (auto *params = GC->getParsedGenericParams()) {
         visitGenericParamList(params);
       }
       return true;
@@ -142,11 +142,10 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
       for (auto &Req: Where->getRequirements())
         if (doIt(Req))
           return true;
-    } else if (!isa<ExtensionDecl>(GC)) {
-      if (const auto GP = GC->getGenericParams())
-        for (auto Req: GP->getTrailingRequirements())
-          if (doIt(Req))
-            return true;
+    } else if (const auto GP = GC->getParsedGenericParams()) {
+      for (auto Req: GP->getTrailingRequirements())
+        if (doIt(Req))
+          return true;
     }
     return false;
   }

lib/AST/Decl.cpp

@@ -992,9 +992,8 @@ GenericContext::GenericContext(DeclContextKind Kind, DeclContext *Parent,
                                GenericParamList *Params)
     : _GenericContext(), DeclContext(Kind, Parent) {
   if (Params) {
-    Parent->getASTContext().evaluator.cacheOutput(
-          GenericParamListRequest{const_cast<GenericContext *>(this)},
-          std::move(Params));
+    Params->setDeclContext(this);
+    GenericParamsAndBit.setPointerAndInt(Params, false);
   }
 }
 
@@ -1020,6 +1019,12 @@ GenericParamList *GenericContext::getGenericParams() const {
                                const_cast<GenericContext *>(this)}, nullptr);
 }
 
+GenericParamList *GenericContext::getParsedGenericParams() const {
+  if (GenericParamsAndBit.getInt())
+    return nullptr;
+  return GenericParamsAndBit.getPointer();
+}
+
 bool GenericContext::hasComputedGenericSignature() const {
   return GenericSigAndBit.getInt();
 }
@@ -1049,8 +1054,8 @@ void GenericContext::setGenericSignature(GenericSignature genericSig) {
 }
 
 SourceRange GenericContext::getGenericTrailingWhereClauseSourceRange() const {
-  if (isGeneric())
-    return getGenericParams()->getTrailingWhereClauseSourceRange();
+  if (auto *params = getParsedGenericParams())
+    return params->getTrailingWhereClauseSourceRange();
   else if (const auto *where = getTrailingWhereClause())
     return where->getSourceRange();
 

lib/AST/NameLookupRequests.cpp

@@ -225,10 +225,13 @@ evaluator::DependencySource GetDestructorRequest::readDependencySource(
 
 Optional<GenericParamList *> GenericParamListRequest::getCachedResult() const {
   auto *decl = std::get<0>(getStorage());
-  if (!decl->GenericParamsAndBit.getInt()) {
-    return None;
-  }
-  return decl->GenericParamsAndBit.getPointer();
+  if (auto *params = decl->GenericParamsAndBit.getPointer())
+    return params;
+
+  if (decl->GenericParamsAndBit.getInt())
+    return nullptr;
+
+  return None;
 }
 
 void GenericParamListRequest::cacheResult(GenericParamList *params) const {

lib/IDE/Formatting.cpp

@@ -485,7 +485,7 @@ class RangeWalker: protected ASTWalker {
       bool SafeToAskForGenerics = !isa<ExtensionDecl>(D) &&
         !isa<ProtocolDecl>(D);
       if (SafeToAskForGenerics) {
-        if (auto *GP = GC->getGenericParams()) {
+        if (auto *GP = GC->getParsedGenericParams()) {
           if (!handleAngles(GP->getLAngleLoc(), GP->getRAngleLoc(), ContextLoc))
             return Stop;
         }
@@ -1583,7 +1583,7 @@ class FormatWalker : public ASTWalker {
         return Ctx;
       if (auto Ctx = getIndentContextFrom(AFD->getParameters(), ContextLoc))
         return Ctx;
-      if (auto Ctx = getIndentContextFrom(AFD->getGenericParams(), ContextLoc, D))
+      if (auto Ctx = getIndentContextFrom(AFD->getParsedGenericParams(), ContextLoc, D))
         return Ctx;
 
       if (TrailingTarget)
@@ -1598,7 +1598,7 @@ class FormatWalker : public ASTWalker {
         return Ctx;
       if (auto Ctx = getIndentContextFromBraces(NTD->getBraces(), ContextLoc, NTD))
         return Ctx;
-      if (auto Ctx = getIndentContextFrom(NTD->getGenericParams(), ContextLoc, D))
+      if (auto Ctx = getIndentContextFrom(NTD->getParsedGenericParams(), ContextLoc, D))
         return Ctx;
       if (auto Ctx = getIndentContextFrom(NTD->getTrailingWhereClause(), ContextLoc, D))
         return Ctx;
@@ -1656,7 +1656,7 @@ class FormatWalker : public ASTWalker {
         return Ctx;
       if (auto Ctx = getIndentContextFrom(SD->getIndices(), ContextLoc))
         return Ctx;
-      if (auto Ctx = getIndentContextFrom(SD->getGenericParams(), ContextLoc, D))
+      if (auto Ctx = getIndentContextFrom(SD->getParsedGenericParams(), ContextLoc, D))
         return Ctx;
 
       if (TrailingTarget)
@@ -1752,7 +1752,7 @@ class FormatWalker : public ASTWalker {
     if (auto *TAD = dyn_cast<TypeAliasDecl>(D)) {
       SourceLoc ContextLoc = TAD->getStartLoc();
 
-      if (auto Ctx = getIndentContextFrom(TAD->getGenericParams(), ContextLoc,
+      if (auto Ctx = getIndentContextFrom(TAD->getParsedGenericParams(), ContextLoc,
                                           D)) {
         return Ctx;
       }