unified-signatures: Can't unify rest parameters

src/rules/unifiedSignaturesRule.ts

@@ -206,7 +206,11 @@ function signaturesDifferBySingleParameter(types1: ts.ParameterDeclaration[], ty
 
  const a = types1[index];
  const b = types2[index];
- return parametersHaveEqualSigils(a, b) ? { kind: "single-parameter-difference", p0: a, p1: b } : undefined;
+ // Can unify `a?: string` and `b?: number`. Can't unify `...args: string[]` and `...args: number[]`.
+ // See https://github.com/Microsoft/TypeScript/issues/5077
+ return parametersHaveEqualSigils(a, b) && a.dotDotDotToken === undefined
+ ? { kind: "single-parameter-difference", p0: a, p1: b }
+ : undefined;
 }
 
 /**

test/rules/unified-signatures/test.d.ts.lint

@@ -36,10 +36,9 @@ interface I {
  b2(x: string): void;
  b2(...x: number[]): void;
 
- // Error if both are rest parameters.
+ // No error if both are rest parameters. (https://github.com/Microsoft/TypeScript/issues/5077)
  b3(...x: number[]): void;
  b3(...x: string[]): void;
- ~~~~~~~~~~~~~~ [These overloads can be combined into one signature taking `number[] | string[]`.]
 
  // Error if only one defines an optional parameter.
  c(): void;