Remove unnecessary annotations/casts/aliases (microsoft#46727)

* Remove unnecessary annotation.

* Remove more unnecessary stuff.

* Remove unnecessary assertion.

Author: DanielRosenwasser

src/compiler/checker.ts

@@ -43062,8 +43062,7 @@ namespace ts {
 
                 // Modifiers are never allowed on properties except for 'async' on a method declaration
                 if (prop.modifiers) {
-                    // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
-                    for (const mod of prop.modifiers!) { // TODO: GH#19955
+                    for (const mod of prop.modifiers) {
                         if (mod.kind !== SyntaxKind.AsyncKeyword || prop.kind !== SyntaxKind.MethodDeclaration) {
                             grammarErrorOnNode(mod, Diagnostics._0_modifier_cannot_be_used_here, getTextOfNode(mod));
                         }

src/services/codefixes/convertToEsModule.ts

@@ -408,9 +408,7 @@ namespace ts.codefix {
                 const importSpecifiers = mapAllOrFail(name.elements, e =>
                     e.dotDotDotToken || e.initializer || e.propertyName && !isIdentifier(e.propertyName) || !isIdentifier(e.name)
                         ? undefined
-                        // (TODO: GH#18217)
-                        // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
-                        : makeImportSpecifier(e.propertyName && (e.propertyName as Identifier).text, e.name.text));
+                        : makeImportSpecifier(e.propertyName && e.propertyName.text, e.name.text));
                 if (importSpecifiers) {
                     return convertedImports([makeImport(/*name*/ undefined, importSpecifiers, moduleSpecifier, quotePreference)]);
                 }

src/services/findAllReferences.ts

@@ -1323,7 +1323,7 @@ namespace ts.FindAllReferences {
             if (!symbol) return undefined;
             for (const token of getPossibleSymbolReferenceNodes(sourceFile, symbol.name, searchContainer)) {
                 if (!isIdentifier(token) || token === definition || token.escapedText !== definition.escapedText) continue;
-                const referenceSymbol: Symbol = checker.getSymbolAtLocation(token)!; // See GH#19955 for why the type annotation is necessary
+                const referenceSymbol = checker.getSymbolAtLocation(token)!;
                 if (referenceSymbol === symbol
                     || checker.getShorthandAssignmentValueSymbol(token.parent) === symbol
                     || isExportSpecifier(token.parent) && getLocalSymbolForExportSpecifier(token, referenceSymbol, token.parent, checker) === symbol) {

src/services/refactors/extractSymbol.ts

@@ -314,8 +314,7 @@ namespace ts.refactor.extractSymbol {
                 return { errors: [createFileDiagnostic(sourceFile, span.start, length, Messages.cannotExtractRange)] };
             }
             const statements: Statement[] = [];
-            const start2 = start; // TODO: GH#18217 Need to alias `start` to get this to compile. See https://github.com/Microsoft/TypeScript/issues/19955#issuecomment-344118248
-            for (const statement of (start2.parent as BlockLike).statements) {
+            for (const statement of start.parent.statements) {
                 if (statement === start || statements.length) {
                     const errors = checkNode(statement);
                     if (errors) {