Clean up code

Author: jakebailey

src/compiler/checker.ts

@@ -7272,7 +7272,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             //
             // If the declaration is in a JS file, then we don't need to do this at all, as there are no annotations besides
             // JSDoc, which are always outside the function declaration, so are not in the parameter scope.
-            let restoreEnclosingDeclaration: (() => void) | undefined;
+            let cleanup: (() => void) | undefined;
             if (
                 context.enclosingDeclaration
                 && signature.declaration
@@ -7292,11 +7292,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 // It'd likely be better to store this somewhere else for isSymbolAccessible, but
                 // since that API _only_ uses the enclosing declaration (and its parents), this is
                 // seems like the best way to inject names into that search process.
-                const locals = context.fakeScopeLocals ??= createSymbolTable();
+                const existingFakeScope = findAncestor(context.enclosingDeclaration, node => !!getNodeLinks(node).fakeScopeForSignatureDeclaration);
+                Debug.assertOptionalNode(existingFakeScope, isBlock);
 
-                // Performance optimization; if this is empty then we're not going to find a fake scope
-                // in the parents of context.enclosingDeclaration, so skip searching later.
-                const couldHaveFakeScopeAncestor = !!locals.size;
+                const locals = existingFakeScope?.locals ?? createSymbolTable();
 
                 let newLocals: __String[] | undefined;
                 for (const param of expandedParams) {
@@ -7311,8 +7310,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         forEach(newLocals, s => locals.delete(s));
                     }
 
-                    if (couldHaveFakeScopeAncestor && findAncestor(context.enclosingDeclaration, node => !!getNodeLinks(node).fakeScopeForSignatureDeclaration)) {
-                        restoreEnclosingDeclaration = removeNewLocals;
+                    if (existingFakeScope) {
+                        cleanup = removeNewLocals;
                     }
                     else {
                         // Use a Block for this; the type of the node doesn't matter so long as it
@@ -7325,7 +7324,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         setParent(fakeScope, saveEnclosingDeclaration);
                         context.enclosingDeclaration = fakeScope;
 
-                        restoreEnclosingDeclaration = () => {
+                        cleanup = () => {
                             context.enclosingDeclaration = saveEnclosingDeclaration;
                             removeNewLocals();
                         };
@@ -7388,7 +7387,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 node.typeArguments = factory.createNodeArray(typeArguments);
             }
 
-            restoreEnclosingDeclaration?.();
+            cleanup?.();
             return node;
         }
 
@@ -48551,7 +48550,6 @@ interface NodeBuilderContext {
     usedSymbolNames?: Set<string>;
     remappedSymbolNames?: Map<SymbolId, string>;
     reverseMappedStack?: ReverseMappedSymbol[];
-    fakeScopeLocals?: SymbolTable;
 }
 
 class SymbolTrackerImpl implements SymbolTracker {