Use Ctx.Id_self and update comments

Author: calda

lib/Sema/CSDiagnostics.cpp

@@ -1376,7 +1376,9 @@ bool MemberAccessOnOptionalBaseFailure::diagnoseAsError() {
     if (auto dotExpr = getAsExpr<UnresolvedDotExpr>(locator->getAnchor())) {
       if (auto base = dotExpr->getBase()) {
         if (auto baseDeclRef = dyn_cast<DeclRefExpr>(base)) {
-          if (baseDeclRef->isImplicit() && baseDeclRef->getDecl()->getBaseIdentifier().is("self")) {
+          ASTContext &Ctx = baseDeclRef->getDecl()->getASTContext();
+          if (baseDeclRef->isImplicit()
+              && baseDeclRef->getDecl()->getName().isSimpleName(Ctx.Id_self)) {
             emitDiagnostic(diag::optional_self_not_unwrapped);
 
             emitDiagnostic(diag::optional_self_chain)

lib/Sema/MiscDiagnostics.cpp

@@ -1591,7 +1591,8 @@ static void diagnoseImplicitSelfUseInClosure(const Expr *E,
 
       // If this decl isn't named "self", then it isn't an implicit self capture
       // and we have no reason to reject it.
-      if (!DRE->getDecl()->getBaseName().getIdentifier().is("self")) {
+      ASTContext &Ctx = DRE->getDecl()->getASTContext();
+      if (!DRE->getDecl()->getName().isSimpleName(Ctx.Id_self)) {
         return false;
       }
 
@@ -1634,11 +1635,11 @@ static void diagnoseImplicitSelfUseInClosure(const Expr *E,
               if (cond.getKind() == StmtConditionElement::CK_PatternBinding) {
                 if (auto optionalPattern = dyn_cast<OptionalSomePattern>(cond.getPattern())) {
                   // if the lhs of the optional binding is `self`...
-                  if (optionalPattern->getSubPattern()->getBoundName().is("self")) {
+                  if (optionalPattern->getSubPattern()->getBoundName() == Ctx.Id_self) {
                     if (auto loadExpr = dyn_cast<LoadExpr>(cond.getInitializer())) {
                       if (auto declRefExpr = dyn_cast<DeclRefExpr>(loadExpr->getSubExpr())) {
                         // and the rhs of the optional binding is `self`...
-                        if (declRefExpr->getDecl()->getBaseIdentifier().is("self")) {
+                        if (declRefExpr->getDecl()->getName().isSimpleName(Ctx.Id_self)) {
                           // then we can permit implicit self in this closure
                           hasCorrectSelfBindingCondition = true;
                         }

lib/Sema/PreCheckExpr.cpp

@@ -761,13 +761,11 @@ Expr *TypeChecker::resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE,
           UDRE->getNameLoc(), NTD, BaseDC,
           DC->mapTypeIntoContext(NTD->getInterfaceType()));
     } else {
-      // If this is an implicit self reference, the `VarDecl` will
-      // currently have a non-optional type. But at this point,
-      // we don't actually know if this is correct (it could be a
-      // weak self capture that hasn't been unwrapped yet).
-      //  - Since we don't know the correct type of self yet,
-      //    we leave this as an UnresolvedDeclRefExpr that is
-      //    populated with the actual type later.
+      // If this is an implicit self reference, we replace the `DeclRefExpr`
+      // with an `UnresolvedDeclRefExpr` to make the type checker take another
+      // pass on the expr. This causes `getParentPatternStmt()` to be populated,
+      // which is required later to validate conditions for permitting
+      // implicit self for `[weak self]` captures.
       bool isClosureImplicitSelfParameter = false;
       if (DC->getContextKind() == DeclContextKind::AbstractClosureExpr)
         if (auto varDecl = dyn_cast<VarDecl>(Base))