/
noUnnecessaryGenericsRule.ts
115 lines (104 loc) · 3.17 KB
/
noUnnecessaryGenericsRule.ts
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import * as Lint from "tslint";
import * as ts from "typescript";
import { failure } from "../util";
export class Rule extends Lint.Rules.TypedRule {
static metadata: Lint.IRuleMetadata = {
ruleName: "no-unnecessary-generics",
description: "Forbids signatures using a generic parameter only once.",
optionsDescription: "Not configurable.",
options: null,
type: "style",
typescriptOnly: true,
};
// eslint-disable-next-line @typescript-eslint/naming-convention
static FAILURE_STRING(typeParameter: string) {
return failure(Rule.metadata.ruleName, `Type parameter ${typeParameter} is used only once.`);
}
// eslint-disable-next-line @typescript-eslint/naming-convention
static FAILURE_STRING_NEVER(typeParameter: string) {
return failure(Rule.metadata.ruleName, `Type parameter ${typeParameter} is never used.`);
}
applyWithProgram(sourceFile: ts.SourceFile, program: ts.Program): Lint.RuleFailure[] {
return this.applyWithFunction(sourceFile, (ctx) => walk(ctx, program.getTypeChecker()));
}
}
function walk(ctx: Lint.WalkContext<void>, checker: ts.TypeChecker): void {
const { sourceFile } = ctx;
sourceFile.forEachChild(function cb(node) {
if (ts.isFunctionLike(node)) {
checkSignature(node);
}
node.forEachChild(cb);
});
function checkSignature(sig: ts.SignatureDeclaration) {
if (!sig.typeParameters) {
return;
}
for (const tp of sig.typeParameters) {
const typeParameter = tp.name.text;
const res = getSoleUse(sig, assertDefined(checker.getSymbolAtLocation(tp.name)), checker);
switch (res.type) {
case "ok":
break;
case "sole":
ctx.addFailureAtNode(res.soleUse, Rule.FAILURE_STRING(typeParameter));
break;
case "never":
ctx.addFailureAtNode(tp, Rule.FAILURE_STRING_NEVER(typeParameter));
break;
default:
assertNever(res);
}
}
}
}
type Result = { type: "ok" | "never" } | { type: "sole"; soleUse: ts.Identifier };
function getSoleUse(sig: ts.SignatureDeclaration, typeParameterSymbol: ts.Symbol, checker: ts.TypeChecker): Result {
const exit = {};
let soleUse: ts.Identifier | undefined;
try {
if (sig.typeParameters) {
for (const tp of sig.typeParameters) {
if (tp.constraint) {
recur(tp.constraint);
}
}
}
for (const param of sig.parameters) {
if (param.type) {
recur(param.type);
}
}
if (sig.type) {
recur(sig.type);
}
} catch (err) {
if (err === exit) {
return { type: "ok" };
}
throw err;
}
return soleUse ? { type: "sole", soleUse } : { type: "never" };
function recur(node: ts.Node): void {
if (ts.isIdentifier(node)) {
if (checker.getSymbolAtLocation(node) === typeParameterSymbol) {
if (soleUse === undefined) {
soleUse = node;
} else {
throw exit;
}
}
} else {
node.forEachChild(recur);
}
}
}
function assertDefined<T>(value: T | undefined): T {
if (value === undefined) {
throw new Error("unreachable");
}
return value;
}
function assertNever(_: never) {
throw new Error("unreachable");
}