[new-rule] Added new invalid-void rule

src/configs/all.ts

@@ -163,6 +163,7 @@ export const rules = {
     "cyclomatic-complexity": true,
     eofline: true,
     indent: { options: ["spaces"] },
+    "invalid-void": true,
     "linebreak-style": { options: "LF" },
     "max-classes-per-file": { options: 1 },
     "max-file-line-count": { options: 1000 },

src/language/rule/abstractRule.ts

@@ -67,7 +67,7 @@ export abstract class AbstractRule implements IRule {
     ): RuleFailure[];
     protected applyWithFunction<T, U>(
         sourceFile: ts.SourceFile,
-        walkFn: (ctx: WalkContext<T | void>, programOrChecker?: U) => void,
+        walkFn: (ctx: WalkContext<T | undefined>, programOrChecker?: U) => void,
         options?: T,
         programOrChecker?: U,
     ): RuleFailure[] {

src/language/walker/walkContext.ts

@@ -19,7 +19,7 @@ import * as ts from "typescript";
 
 import { Fix, RuleFailure } from "../rule/rule";
 
-export class WalkContext<T = void> {
+export class WalkContext<T = undefined> {
     public readonly failures: RuleFailure[] = [];
 
     constructor(

src/language/walker/walker.ts

@@ -27,7 +27,7 @@ export interface IWalker {
     getFailures(): RuleFailure[];
 }
 
-export abstract class AbstractWalker<T = void> extends WalkContext<T> implements IWalker {
+export abstract class AbstractWalker<T = undefined> extends WalkContext<T> implements IWalker {
     public abstract walk(sourceFile: ts.SourceFile): void;
 
     public getSourceFile() {

src/rules/invalidVoidRule.ts

@@ -0,0 +1,86 @@
+/**
+ * @license
+ * Copyright 2019 Palantir Technologies, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as ts from "typescript";
+
+import * as Lint from "../index";
+
+export class Rule extends Lint.Rules.AbstractRule {
+    /* tslint:disable:object-literal-sort-keys */
+    public static metadata: Lint.IRuleMetadata = {
+        ruleName: "invalid-void",
+        description: Lint.Utils.dedent`
+            Disallows usage of \`void\` type outside of return type.
+            If \`void\` is used as return type, it shouldn't be a part of intersection/union type.`,
+        rationale: Lint.Utils.dedent`
+            The \`void\` type means "nothing" or that a function does not return any value,
+            in contra with implicit \`undefined\` type which means that a function returns a value \`undefined\`.
+            So "nothing" cannot be mixed with any other types.
+            If you need this - use \`undefined\` type instead.`,
+        hasFix: false,
+        optionsDescription: "Not configurable.",
+        options: null,
+        optionExamples: [true],
+        type: "maintainability",
+        typescriptOnly: true,
+    };
+    /* tslint:enable:object-literal-sort-keys */
+
+    public static FAILURE_STRING = "void is not a valid type other than return types";
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithFunction(sourceFile, walk);
+    }
+}
+
+const failedKinds = new Set([
+    ts.SyntaxKind.PropertySignature,
+    ts.SyntaxKind.PropertyDeclaration,
+
+    ts.SyntaxKind.VariableDeclaration,
+    ts.SyntaxKind.TypeAliasDeclaration,
+
+    ts.SyntaxKind.IntersectionType,
+    ts.SyntaxKind.UnionType,
+
+    ts.SyntaxKind.Parameter,
+    ts.SyntaxKind.TypeParameter,
+
+    ts.SyntaxKind.AsExpression,
+    ts.SyntaxKind.TypeAssertionExpression,
+
+    ts.SyntaxKind.TypeOperator,
+    ts.SyntaxKind.ArrayType,
+
+    ts.SyntaxKind.MappedType,
+    ts.SyntaxKind.ConditionalType,
+
+    ts.SyntaxKind.TypeReference,
+
+    ts.SyntaxKind.NewExpression,
+    ts.SyntaxKind.CallExpression,
+]);
+
+function walk(ctx: Lint.WalkContext): void {
+    ts.forEachChild(ctx.sourceFile, function cb(node: ts.Node) {
+        if (node.kind === ts.SyntaxKind.VoidKeyword && failedKinds.has(node.parent.kind)) {
+            ctx.addFailureAtNode(node, Rule.FAILURE_STRING);
+        }
+
+        ts.forEachChild(node, cb);
+    });
+}

test/rules/invalid-void/test.ts.lint

@@ -0,0 +1,121 @@
+function func(): void {}
+
+type NormalType = () => void;
+
+let normalArrow = (): void => { }
+
+let ughThisThing = void 0;
+
+function takeThing(thing: undefined) { }
+takeThing(void 0);
+
+function takeVoid(thing: void) { }
+                         ~~~~ [0]
+
+
+const arrowGeneric = <T extends void>(arg: T) => { }
+                                ~~~~ [0]
+#if typescript >= 2.3.0
+const arrowGeneric1 = <T = void>(arg: T) => { }
+                           ~~~~ [0]
+const arrowGeneric2 = <T extends void = void>(arg: T) => { }
+                                 ~~~~ [0]
+                                        ~~~~ [0]
+#endif
+
+#if typescript >= 2.3.0
+function functionGeneric<T extends void>(arg: T) {}
+                                   ~~~~ [0]
+
+function functionGeneric1<T = void>(arg: T) {}
+                              ~~~~ [0]
+function functionGeneric2<T extends void = void>(arg: T) {}
+                                    ~~~~ [0]
+                                           ~~~~ [0]
+#endif
+
+declare function functionDeclaration<T extends void>(arg: T): void;
+                                               ~~~~ [0]
+#if typescript >= 2.3.0
+declare function functionDeclaration1<T = void>(arg: T): void;
+                                          ~~~~ [0]
+declare function functionDeclaration2<T extends void = void>(arg: T): void;
+                                                ~~~~ [0]
+                                                       ~~~~ [0]
+#endif
+
+
+functionGeneric<void>(undefined);
+                ~~~~ [0]
+
+declare function voidArray(args: void[]): void[];
+                                 ~~~~ [0]
+                                          ~~~~ [0]
+
+let value = undefined as void;
+                         ~~~~ [0]
+
+let value = <void>undefined;
+             ~~~~ [0]
+
+function takesThings(...things: void[]): void { }
+                                ~~~~ [0]
+
+type KeyofVoid = keyof void;
+                       ~~~~[0]
+
+interface Interface {
+    lambda: () => void;
+    voidProp: void;
+              ~~~~ [0]
+}
+
+class ClassName {
+    private readonly propName: void;
+                               ~~~~ [0]
+}
+
+let invalidMap: Map<string, void> = new Map<string, void>();
+                            ~~~~ [0]
+                                                    ~~~~ [0]
+
+let letVoid: void;
+             ~~~~ [0]
+
+type VoidType = void;
+                ~~~~ [0]
+
+class OtherClassName {
+    private propName: VoidType;
+}
+
+type UnionType = string | number;
+type UnionType2 = string | number | void;
+                                    ~~~~ [0]
+
+type UnionType3 = string | (number & any | (string | void));
+                                                     ~~~~ [0]
+
+type IntersectionType = string & number & void;
+                                          ~~~~ [0]
+
+#if typescript >= 2.8.0
+type MappedType<T> = {
+    [K in keyof T]: void;
+                    ~~~~ [0]
+}
+type ConditionalType<T> = {
+    [K in keyof T]: T[K] extends string ? void : string;
+                                          ~~~~ [0]
+}
+#endif
+
+#if typescript >= 3.4.0
+type ManyVoid = readonly void[];
+                         ~~~~ [0]
+
+function foo(arr: readonly void[]) { }
+                           ~~~~ [0]
+#endif
+
+[0]: void is not a valid type other than return types

test/rules/invalid-void/tslint.json

@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "invalid-void": true
+  }
+}