Consistently add undefined/missing to optional tuple element types (#…

…50831)

* Consistently add undefined/missing type to optional tuple elements

* Accept new baselines

* Add regression test

src/compiler/checker.ts

@@ -14660,7 +14660,7 @@ namespace ts {
                 if (flags & (ElementFlags.Optional | ElementFlags.Rest)) {
                     lastOptionalOrRestIndex = expandedFlags.length;
                 }
-                expandedTypes.push(type);
+                expandedTypes.push(flags & ElementFlags.Optional ? addOptionality(type, /*isProperty*/ true) : type);
                 expandedFlags.push(flags);
                 if (expandedDeclarations && declaration) {
                     expandedDeclarations.push(declaration);
@@ -21705,7 +21705,8 @@ namespace ts {
 
         function getOptionalType(type: Type, isProperty = false): Type {
             Debug.assert(strictNullChecks);
-            return type.flags & TypeFlags.Undefined ? type : getUnionType([type, isProperty ? missingType : undefinedType]);
+            const missingOrUndefined = isProperty ? missingType : undefinedType;
+            return type.flags & TypeFlags.Undefined || type.flags & TypeFlags.Union && (type as UnionType).types[0] === missingOrUndefined ? type : getUnionType([type, missingOrUndefined]);
         }
 
         function getGlobalNonNullableTypeInstantiation(type: Type) {

tests/baselines/reference/mappedTypesArraysTuples.types

@@ -7,7 +7,7 @@ type Boxified<T> = { [P in keyof T]: Box<T[P]> };
 >Boxified : Boxified<T>
 
 type T00 = Boxified<[number, string?, ...boolean[]]>;
->T00 : [Box<number>, Box<string | undefined>?, ...Box<boolean>[]]
+>T00 : [Box<number>, (Box<string | undefined> | undefined)?, ...Box<boolean>[]]
 
 type T01 = Partial<[number, string?, ...boolean[]]>;
 >T01 : [(number | undefined)?, (string | undefined)?, ...(boolean | undefined)[]]

tests/baselines/reference/optionalTupleElementsAndUndefined.js

@@ -0,0 +1,33 @@
+//// [optionalTupleElementsAndUndefined.ts]
+// Repro from #50753
+
+type UnNullify<T> = { [K in keyof T]: NonNullable<T[K]> };
+
+type Foo = UnNullify<[a: 1, b?: 2 | undefined]>;
+
+type Test = [a: 1, b?: 2] extends Foo ? true : false;  // true
+
+// Types in the following declarations should be identical
+
+var v: [1, 2?];
+var v: [1, (2 | undefined)?];
+var v: [a: 1, b?: 2];
+var v: [a: 1, b?: 2 | undefined];
+var v: UnNullify<[1, 2?]>;
+var v: UnNullify<[1, (2 | undefined)?]>;
+var v: UnNullify<[a: 1, b?: 2]>;
+var v: UnNullify<[a: 1, b?: 2 | undefined]>;
+
+
+//// [optionalTupleElementsAndUndefined.js]
+"use strict";
+// Repro from #50753
+// Types in the following declarations should be identical
+var v;
+var v;
+var v;
+var v;
+var v;
+var v;
+var v;
+var v;

tests/baselines/reference/optionalTupleElementsAndUndefined.symbols

@@ -0,0 +1,50 @@
+=== tests/cases/compiler/optionalTupleElementsAndUndefined.ts ===
+// Repro from #50753
+
+type UnNullify<T> = { [K in keyof T]: NonNullable<T[K]> };
+>UnNullify : Symbol(UnNullify, Decl(optionalTupleElementsAndUndefined.ts, 0, 0))
+>T : Symbol(T, Decl(optionalTupleElementsAndUndefined.ts, 2, 15))
+>K : Symbol(K, Decl(optionalTupleElementsAndUndefined.ts, 2, 23))
+>T : Symbol(T, Decl(optionalTupleElementsAndUndefined.ts, 2, 15))
+>NonNullable : Symbol(NonNullable, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(optionalTupleElementsAndUndefined.ts, 2, 15))
+>K : Symbol(K, Decl(optionalTupleElementsAndUndefined.ts, 2, 23))
+
+type Foo = UnNullify<[a: 1, b?: 2 | undefined]>;
+>Foo : Symbol(Foo, Decl(optionalTupleElementsAndUndefined.ts, 2, 58))
+>UnNullify : Symbol(UnNullify, Decl(optionalTupleElementsAndUndefined.ts, 0, 0))
+
+type Test = [a: 1, b?: 2] extends Foo ? true : false;  // true
+>Test : Symbol(Test, Decl(optionalTupleElementsAndUndefined.ts, 4, 48))
+>Foo : Symbol(Foo, Decl(optionalTupleElementsAndUndefined.ts, 2, 58))
+
+// Types in the following declarations should be identical
+
+var v: [1, 2?];
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+
+var v: [1, (2 | undefined)?];
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+
+var v: [a: 1, b?: 2];
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+
+var v: [a: 1, b?: 2 | undefined];
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+
+var v: UnNullify<[1, 2?]>;
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+>UnNullify : Symbol(UnNullify, Decl(optionalTupleElementsAndUndefined.ts, 0, 0))
+
+var v: UnNullify<[1, (2 | undefined)?]>;
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+>UnNullify : Symbol(UnNullify, Decl(optionalTupleElementsAndUndefined.ts, 0, 0))
+
+var v: UnNullify<[a: 1, b?: 2]>;
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+>UnNullify : Symbol(UnNullify, Decl(optionalTupleElementsAndUndefined.ts, 0, 0))
+
+var v: UnNullify<[a: 1, b?: 2 | undefined]>;
+>v : Symbol(v, Decl(optionalTupleElementsAndUndefined.ts, 10, 3), Decl(optionalTupleElementsAndUndefined.ts, 11, 3), Decl(optionalTupleElementsAndUndefined.ts, 12, 3), Decl(optionalTupleElementsAndUndefined.ts, 13, 3), Decl(optionalTupleElementsAndUndefined.ts, 14, 3) ... and 3 more)
+>UnNullify : Symbol(UnNullify, Decl(optionalTupleElementsAndUndefined.ts, 0, 0))
+

tests/baselines/reference/optionalTupleElementsAndUndefined.types

@@ -0,0 +1,40 @@
+=== tests/cases/compiler/optionalTupleElementsAndUndefined.ts ===
+// Repro from #50753
+
+type UnNullify<T> = { [K in keyof T]: NonNullable<T[K]> };
+>UnNullify : UnNullify<T>
+
+type Foo = UnNullify<[a: 1, b?: 2 | undefined]>;
+>Foo : [a: 1, b?: 2 | undefined]
+
+type Test = [a: 1, b?: 2] extends Foo ? true : false;  // true
+>Test : true
+>true : true
+>false : false
+
+// Types in the following declarations should be identical
+
+var v: [1, 2?];
+>v : [1, (2 | undefined)?]
+
+var v: [1, (2 | undefined)?];
+>v : [1, (2 | undefined)?]
+
+var v: [a: 1, b?: 2];
+>v : [1, (2 | undefined)?]
+
+var v: [a: 1, b?: 2 | undefined];
+>v : [1, (2 | undefined)?]
+
+var v: UnNullify<[1, 2?]>;
+>v : [1, (2 | undefined)?]
+
+var v: UnNullify<[1, (2 | undefined)?]>;
+>v : [1, (2 | undefined)?]
+
+var v: UnNullify<[a: 1, b?: 2]>;
+>v : [1, (2 | undefined)?]
+
+var v: UnNullify<[a: 1, b?: 2 | undefined]>;
+>v : [1, (2 | undefined)?]
+

tests/baselines/reference/variadicTuples1.types

@@ -409,7 +409,7 @@ type Arrayify<T> = { [P in keyof T]: T[P][] };
 >Arrayify : Arrayify<T>
 
 type TM1<U extends unknown[]> = Arrayify<readonly [string, number?, ...U, ...boolean[]]>;  // [string[], (number | undefined)[]?, Arrayify<U>, ...boolean[][]]
->TM1 : readonly [string[], (number | undefined)[]?, ...Arrayify<U>, ...boolean[][]]
+>TM1 : readonly [string[], ((number | undefined)[] | undefined)?, ...Arrayify<U>, ...boolean[][]]
 
 type TP1<T extends unknown[]> = Partial<[string, ...T, number]>;  // [string?, Partial<T>, number?]
 >TP1 : [(string | undefined)?, ...Partial<T>, (number | undefined)?]

tests/cases/compiler/optionalTupleElementsAndUndefined.ts

@@ -0,0 +1,20 @@
+// @strict: true
+
+// Repro from #50753
+
+type UnNullify<T> = { [K in keyof T]: NonNullable<T[K]> };
+
+type Foo = UnNullify<[a: 1, b?: 2 | undefined]>;
+
+type Test = [a: 1, b?: 2] extends Foo ? true : false;  // true
+
+// Types in the following declarations should be identical
+
+var v: [1, 2?];
+var v: [1, (2 | undefined)?];
+var v: [a: 1, b?: 2];
+var v: [a: 1, b?: 2 | undefined];
+var v: UnNullify<[1, 2?]>;
+var v: UnNullify<[1, (2 | undefined)?]>;
+var v: UnNullify<[a: 1, b?: 2]>;
+var v: UnNullify<[a: 1, b?: 2 | undefined]>;