Port babel-parser changes from 2020-04-12 to 2020-07-22

src/parser/plugins/typescript.ts

@@ -367,6 +367,7 @@ function tsParseMappedType(): void {
 function tsParseTupleType(): void {
   expect(tt.bracketL);
   while (!eat(tt.bracketR) && !state.error) {
+    // Do not validate presence of either none or only labeled elements
     tsParseTupleElementType();
     eat(tt.comma);
   }
@@ -376,11 +377,17 @@ function tsParseTupleElementType(): void {
   // parses `...TsType[]`
   if (eat(tt.ellipsis)) {
     tsParseType();
-    return;
+  } else {
+    // parses `TsType?`
+    tsParseType();
+    eat(tt.question);
+  }
+
+  // The type we parsed above was actually a label
+  if (eat(tt.colon)) {
+    // Labeled tuple types must affix the label with `...` or `?`, so no need to handle those here
+    tsParseType();
   }
-  // parses `TsType?`
-  tsParseType();
-  eat(tt.question);
 }
 
 function tsParseParenthesizedType(): void {

test/typescript-test.ts

@@ -2200,4 +2200,17 @@ describe("typescript transform", () => {
     `,
     );
   });
+
+  it("properly removes labeled tuple types", () => {
+    assertTypeScriptResult(
+      `
+      type T1 = [x: number, y?: number, ...rest: number[]];
+      function f(args: [s?: string, ...ns: number[]]) {}
+    `,
+      `"use strict";
+
+      function f(args) {}
+    `,
+    );
+  });
 });