Enable 'no-unnecessary-type-assertion' rule (#2670)

src/linter.ts

@@ -106,6 +106,7 @@ class Linter {
 
         // add rule severity to failures
         const ruleSeverityMap = new Map(enabledRules.map((rule) => {
+            // tslint:disable-next-line no-unnecessary-type-assertion
             return [rule.getOptions().ruleName, rule.getOptions().ruleSeverity] as [string, RuleSeverity];
         }));
 

src/rules/callableTypesRule.ts

@@ -72,7 +72,7 @@ function noSupertype(node: ts.InterfaceDeclaration): boolean {
     if (node.heritageClauses.length !== 1) {
         return false;
     }
-    const expr = node.heritageClauses[0].types![0].expression;
+    const expr = node.heritageClauses[0].types[0].expression;
     return isIdentifier(expr) && expr.text === "Function";
 }
 

src/rules/indentRule.ts

@@ -174,7 +174,7 @@ function walk(ctx: Lint.WalkContext<Options>): void {
             ? new RegExp(`^( {${size}})+( {1,${size - 1}})?`, "g")
             : /\t/g;
         const replacement = fullLeadingWhitespace.replace(replaceRegExp, (match) =>
-            (tabs ? "\t" : " ".repeat(size)).repeat(Math.ceil(match.length / size!)));
+            (tabs ? "\t" : " ".repeat(size)).repeat(Math.ceil(match.length / size)));
         return new Lint.Replacement(lineStart, fullLeadingWhitespace.length, replacement);
     }
 }

src/rules/memberOrderingRule.ts

@@ -394,7 +394,7 @@ function categoryFromOption(orderOption: MemberCategoryJson[] | string): MemberC
         return orderOption;
     }
 
-    const preset = PRESETS.get(orderOption as string);
+    const preset = PRESETS.get(orderOption);
     if (preset === undefined) {
         throw new Error(`Bad order: ${JSON.stringify(orderOption)}`);
     }

src/rules/noEmptyInterfaceRule.ts

@@ -46,9 +46,8 @@ function walk(ctx: Lint.WalkContext<void>) {
         if (isInterfaceDeclaration(node) &&
             node.members.length === 0 &&
             (node.heritageClauses === undefined ||
-             node.heritageClauses[0].types === undefined ||
              // allow interfaces that extend 2 or more interfaces
-             node.heritageClauses[0].types!.length < 2)) {
+             node.heritageClauses[0].types.length < 2)) {
             return ctx.addFailureAtNode(node.name,
                 node.heritageClauses !== undefined ? Rule.FAILURE_STRING_FOR_EXTENDS : Rule.FAILURE_STRING);
         }

src/rules/noStringThrowRule.ts

@@ -46,7 +46,7 @@ function walk(ctx: Lint.WalkContext<void>): void {
     const { sourceFile } = ctx;
     return ts.forEachChild(ctx.sourceFile, function cb(node: ts.Node): void {
         if (isThrowStatement(node)) {
-            const { expression } = node as ts.ThrowStatement;
+            const { expression } = node;
             if (isString(expression)) {
                 ctx.addFailureAtNode(node, Rule.FAILURE_STRING, [
                     Lint.Replacement.appendText(expression.getStart(sourceFile), "new Error("),

src/rules/noUnusedVariableRule.ts

@@ -117,7 +117,7 @@ function walk(ctx: Lint.WalkContext<void>, program: ts.Program, { checkParameter
         const failure = ts.flattenDiagnosticMessageText(diag.messageText, "\n");
 
         if (kind === UnusedKind.VARIABLE_OR_PARAMETER) {
-            const importName = findImport(diag.start!, sourceFile);
+            const importName = findImport(diag.start, sourceFile);
             if (importName !== undefined) {
                 if (isImportUsed(importName, sourceFile, checker)) {
                     continue;
@@ -138,7 +138,7 @@ function walk(ctx: Lint.WalkContext<void>, program: ts.Program, { checkParameter
             }
         }
 
-        ctx.addFailureAt(diag.start!, diag.length!, failure);
+        ctx.addFailureAt(diag.start, diag.length, failure);
     }
 
     if (importSpecifierFailures.size !== 0) {

src/rules/onlyArrowFunctionsRule.ts

@@ -100,7 +100,7 @@ function functionIsExempt(node: ts.FunctionLikeDeclaration): boolean {
 function hasThisParameter(node: ts.FunctionLikeDeclaration): boolean {
     const first = node.parameters[0];
     return first !== undefined && first.name.kind === ts.SyntaxKind.Identifier &&
-        (first.name as ts.Identifier).originalKeywordKind === ts.SyntaxKind.ThisKeyword;
+        first.name.originalKeywordKind === ts.SyntaxKind.ThisKeyword;
 }
 
 function usesThisInBody(node: ts.Node): boolean {

src/rules/preferConstRule.ts

@@ -64,8 +64,7 @@ export class Rule extends Lint.Rules.AbstractRule {
 
     public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
         const options: Options = {
-            destructuringAll: this.ruleArguments.length !== 0 &&
-                (this.ruleArguments[0] as any).destructuring === OPTION_DESTRUCTURING_ALL,
+            destructuringAll: this.ruleArguments.length !== 0 && this.ruleArguments[0].destructuring === OPTION_DESTRUCTURING_ALL,
         };
         const preferConstWalker = new PreferConstWalker(sourceFile, this.ruleName, options);
         return this.applyWithWalker(preferConstWalker);
@@ -232,7 +231,7 @@ class PreferConstWalker extends Lint.AbstractWalker<Options> {
                                 this.scope.reassigned.add((property.name as ts.Identifier).text);
                             } else {
                                 // handle `...(variable)`
-                                this.handleExpression(property.expression!);
+                                this.handleExpression(property.expression);
                             }
                             break;
                         default:
@@ -324,7 +323,7 @@ class PreferConstWalker extends Lint.AbstractWalker<Options> {
                     !info.declarationInfo.reassignedSiblings &&
                     info.declarationInfo.isBlockScoped &&
                     !appliedFixes.has(info.declarationInfo.declarationList)) {
-                    fix = new Lint.Replacement(info.declarationInfo.declarationList!.getStart(this.sourceFile), 3, "const");
+                    fix = new Lint.Replacement(info.declarationInfo.declarationList.getStart(this.sourceFile), 3, "const");
                     // add only one fixer per VariableDeclarationList
                     appliedFixes.add(info.declarationInfo.declarationList);
                 }

src/rules/semicolonRule.ts

@@ -129,7 +129,7 @@ abstract class SemicolonWalker extends Lint.AbstractWalker<Options> {
         if (this.sourceFile.text[node.end - 1] !== ";") {
             return;
         }
-        const lastToken = utils.getPreviousToken(node.getLastToken(this.sourceFile)!, this.sourceFile)!;
+        const lastToken = utils.getPreviousToken(node.getLastToken(this.sourceFile), this.sourceFile)!;
         // yield does not continue on the next line if there is no yielded expression
         if (lastToken.kind === ts.SyntaxKind.YieldKeyword && lastToken.parent!.kind === ts.SyntaxKind.YieldExpression ||
             // arrow functions with block as body don't continue on the next line

src/rules/strictBooleanExpressionsRule.ts

@@ -418,7 +418,7 @@ function showLocation(n: Location): string {
         case ts.SyntaxKind.DoStatement:
             return "'do-while' condition";
         case ts.SyntaxKind.BinaryExpression:
-            return `operand for the '${binaryBooleanExpressionKind(n as ts.BinaryExpression)}' operator`;
+            return `operand for the '${binaryBooleanExpressionKind(n)}' operator`;
     }
 }
 

src/rules/trailingCommaRule.ts

@@ -25,7 +25,7 @@ type OptionName = "arrays" | "exports" | "functions" | "imports" | "objects" | "
 type CustomOptionValue = Record<OptionName, OptionValue>;
 type Options = Record<"multiline" | "singleline", CustomOptionValue>;
 
-const defaultOptions: CustomOptionValue = fillOptions("ignore" as "ignore");
+const defaultOptions: CustomOptionValue = fillOptions("ignore" as "ignore"); // tslint:disable-line no-unnecessary-type-assertion
 
 function fillOptions<T>(value: T): Record<OptionName, T> {
     return {

src/runner.ts

@@ -251,7 +251,7 @@ async function tryReadFile(filename: string, logger: Logger): Promise<string | u
 function showDiagnostic({ file, start, category, messageText }: ts.Diagnostic, program: ts.Program, outputAbsolutePaths: boolean): string {
     let message = ts.DiagnosticCategory[category];
     if (file) {
-        const {line, character} = file.getLineAndCharacterOfPosition(start!);
+        const {line, character} = file.getLineAndCharacterOfPosition(start);
         const currentDirectory = program.getCurrentDirectory();
         const filePath = outputAbsolutePaths
             ? path.resolve(currentDirectory, file.fileName)

src/test/lintError.ts

@@ -42,5 +42,5 @@ export function errorComparator(err1: LintError, err2: LintError) {
 }
 
 export function lintSyntaxError(message: string) {
-    return new Error(`Lint File Syntax Error: ${message}`) as Error;
+    return new Error(`Lint File Syntax Error: ${message}`);
 }

src/tslint-cli.ts

@@ -203,7 +203,7 @@ commander.on("--help", () => {
 const parsed = commander.parseOptions(process.argv.slice(2));
 commander.args = parsed.args;
 if (parsed.unknown.length !== 0) {
-    (commander.parseArgs as any)([], parsed.unknown);
+    (commander.parseArgs as (args: string[], unknown: string[]) => void)([], parsed.unknown);
 }
 const argv = commander.opts() as any as Argv;
 

test/configurationTests.ts

@@ -321,8 +321,8 @@ describe("Configuration", () => {
             const config = loadConfigurationFromPath("./test/config/tslint-extends-package-two-levels.json");
 
             assert.lengthOf(config.rulesDirectory, 2);
-            assert.isTrue(fs.existsSync(config.rulesDirectory![0]));
-            assert.isTrue(fs.existsSync(config.rulesDirectory![1]));
+            assert.isTrue(fs.existsSync(config.rulesDirectory[0]));
+            assert.isTrue(fs.existsSync(config.rulesDirectory[1]));
 
             const expectedConfig = getEmptyConfig();
             expectedConfig.rules.set("always-fail", { ruleSeverity: "off" });

tslint.json

@@ -41,7 +41,6 @@
     "no-null-keyword": false,
     "no-require-imports": false,
     "no-unbound-method": false,
-    "no-unnecessary-type-assertion": false,
     "no-unnecessary-qualifier": false,
     "no-use-before-declare": false,
     "no-void-expression": false,