Preserve partially typed tuple names in more places (microsoft#55789)

Author: jakebailey

src/compiler/checker.ts

@@ -33356,8 +33356,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (arg.kind === SyntaxKind.SyntheticExpression && (arg as SyntheticExpression).tupleNameSource) {
                 names.push((arg as SyntheticExpression).tupleNameSource!);
             }
+            else {
+                names.push(undefined);
+            }
         }
-        return createTupleType(types, flags, inConstContext && !someType(restType, isMutableArrayLikeType), length(names) === length(types) ? names : undefined);
+        return createTupleType(types, flags, inConstContext && !someType(restType, isMutableArrayLikeType), names);
     }
 
     function checkTypeArguments(signature: Signature, typeArgumentNodes: readonly TypeNode[], reportErrors: boolean, headMessage?: DiagnosticMessage): Type[] | undefined {
@@ -35741,12 +35744,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 types.push(restType);
                 flags.push(ElementFlags.Variadic);
             }
-            const name = getNameableDeclarationAtPosition(source, i);
-            if (name) {
-                names.push(name);
-            }
+            names.push(getNameableDeclarationAtPosition(source, i));
         }
-        return createTupleType(types, flags, readonly, length(names) === length(types) ? names : undefined);
+        return createTupleType(types, flags, readonly, names);
     }
 
     // Return the number of parameters in a signature. The rest parameter, if present, counts as one

tests/baselines/reference/argumentsReferenceInFunction1_Js.errors.txt

@@ -1,5 +1,5 @@
 index.js(1,25): error TS7006: Parameter 'f' implicitly has an 'any' type.
-index.js(13,29): error TS2345: Argument of type 'IArguments' is not assignable to parameter of type '[any?, ...any[]]'.
+index.js(13,29): error TS2345: Argument of type 'IArguments' is not assignable to parameter of type '[f?: any, ...any[]]'.
 
 
 ==== index.js (2 errors) ====
@@ -19,6 +19,6 @@ index.js(13,29): error TS2345: Argument of type 'IArguments' is not assignable t
     const debuglog = function() {
       return format.apply(null, arguments);
                                 ~~~~~~~~~
-!!! error TS2345: Argument of type 'IArguments' is not assignable to parameter of type '[any?, ...any[]]'.
+!!! error TS2345: Argument of type 'IArguments' is not assignable to parameter of type '[f?: any, ...any[]]'.
     };
 

tests/baselines/reference/partiallyNamedTuples3.js

@@ -0,0 +1,17 @@
+//// [tests/cases/conformance/types/tuple/named/partiallyNamedTuples3.ts] ////
+
+//// [partiallyNamedTuples3.ts]
+declare const tuple: [number, name: string, boolean, value: number, string];
+
+const output = ((...args) => args)(...tuple);
+
+
+//// [partiallyNamedTuples3.js]
+"use strict";
+var output = (function () {
+    var args = [];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        args[_i] = arguments[_i];
+    }
+    return args;
+}).apply(void 0, tuple);

tests/baselines/reference/partiallyNamedTuples3.symbols

@@ -0,0 +1,12 @@
+//// [tests/cases/conformance/types/tuple/named/partiallyNamedTuples3.ts] ////
+
+=== partiallyNamedTuples3.ts ===
+declare const tuple: [number, name: string, boolean, value: number, string];
+>tuple : Symbol(tuple, Decl(partiallyNamedTuples3.ts, 0, 13))
+
+const output = ((...args) => args)(...tuple);
+>output : Symbol(output, Decl(partiallyNamedTuples3.ts, 2, 5))
+>args : Symbol(args, Decl(partiallyNamedTuples3.ts, 2, 17))
+>args : Symbol(args, Decl(partiallyNamedTuples3.ts, 2, 17))
+>tuple : Symbol(tuple, Decl(partiallyNamedTuples3.ts, 0, 13))
+

tests/baselines/reference/partiallyNamedTuples3.types

@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/types/tuple/named/partiallyNamedTuples3.ts] ////
+
+=== partiallyNamedTuples3.ts ===
+declare const tuple: [number, name: string, boolean, value: number, string];
+>tuple : [number, name: string, boolean, value: number, string]
+
+const output = ((...args) => args)(...tuple);
+>output : [number, name: string, boolean, value: number, string]
+>((...args) => args)(...tuple) : [number, name: string, boolean, value: number, string]
+>((...args) => args) : (args_0: number, name: string, args_2: boolean, value: number, args_4: string) => [number, name: string, boolean, value: number, string]
+>(...args) => args : (args_0: number, name: string, args_2: boolean, value: number, args_4: string) => [number, name: string, boolean, value: number, string]
+>args : [number, name: string, boolean, value: number, string]
+>args : [number, name: string, boolean, value: number, string]
+>...tuple : string | number | boolean
+>tuple : [number, name: string, boolean, value: number, string]
+

tests/baselines/reference/restTuplesFromContextualTypes.types

@@ -265,8 +265,8 @@ f3((a, b, c) => {})
 f3((...x) => {})
 >f3((...x) => {}) : void
 >f3 : (cb: (x: number, args_0: boolean, ...args_1: string[]) => void) => void
->(...x) => {} : (x_0: number, x_1: boolean, ...x_2: string[]) => void
->x : [number, boolean, ...string[]]
+>(...x) => {} : (x: number, x_1: boolean, ...x_2: string[]) => void
+>x : [x: number, boolean, ...string[]]
 
 f3((a, ...x) => {})
 >f3((a, ...x) => {}) : void

tests/cases/conformance/types/tuple/named/partiallyNamedTuples3.ts

@@ -0,0 +1,6 @@
+// @strict: true
+// @lib: esnext
+
+declare const tuple: [number, name: string, boolean, value: number, string];
+
+const output = ((...args) => args)(...tuple);