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Fix issues + Support template literal types as discriminants #46137

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Sep 30, 2021
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Fix issues + Support template literal types as discriminants #46137

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7f34792
Fix issues + Support template literal types in discriminants
ahejlsberg Sep 29, 2021
e1907a2
Add tests
ahejlsberg Sep 29, 2021
955fda5
Address CR feedback
ahejlsberg Sep 29, 2021
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44 changes: 30 additions & 14 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -12029,7 +12029,7 @@ namespace ts {
else if (type !== firstType) {
checkFlags |= CheckFlags.HasNonUniformType;
}
if (isLiteralType(type)) {
if (isLiteralType(type) || isPatternLiteralType(type)) {
checkFlags |= CheckFlags.HasLiteralType;
}
if (type.flags & TypeFlags.Never) {
Expand Down Expand Up @@ -18935,6 +18935,9 @@ namespace ts {
}
else if (target.flags & TypeFlags.TemplateLiteral) {
if (source.flags & TypeFlags.TemplateLiteral) {
if (relation === comparableRelation) {
return templateLiteralTypesDefinitelyUnrelated(source as TemplateLiteralType, target as TemplateLiteralType) ? Ternary.False : Ternary.True;
}
// Report unreliable variance for type variables referenced in template literal type placeholders.
// For example, `foo-${number}` is related to `foo-${string}` even though number isn't related to string.
instantiateType(source, makeFunctionTypeMapper(reportUnreliableMarkers));
Expand Down Expand Up @@ -18974,11 +18977,10 @@ namespace ts {
return result;
}
}
else if (source.flags & TypeFlags.TemplateLiteral) {
else if (source.flags & TypeFlags.TemplateLiteral && !(target.flags & TypeFlags.Object)) {
if (!(target.flags & TypeFlags.TemplateLiteral)) {
const baseConstraint = getBaseConstraintOfType(source);
const constraint = baseConstraint && baseConstraint !== source ? baseConstraint : stringType;
if (result = isRelatedTo(constraint, target, reportErrors)) {
const constraint = getBaseConstraintOfType(source);
if (constraint && constraint !== source && (result = isRelatedTo(constraint, target, reportErrors))) {
resetErrorInfo(saveErrorInfo);
return result;
}
Expand Down Expand Up @@ -21349,6 +21351,18 @@ namespace ts {
return !!(type.symbol && some(type.symbol.declarations, hasSkipDirectInferenceFlag));
}

function templateLiteralTypesDefinitelyUnrelated(source: TemplateLiteralType, target: TemplateLiteralType) {
// Two template literal types with diffences in their starting or ending text spans are definitely unrelated.
const sourceStart = source.texts[0];
const targetStart = target.texts[0];
const sourceEnd = source.texts[source.texts.length - 1];
const targetEnd = target.texts[target.texts.length - 1];
const startLen = Math.min(sourceStart.length, targetStart.length);
const endLen = Math.min(sourceEnd.length, targetEnd.length);
return sourceStart.slice(0, startLen) !== targetStart.slice(0, startLen) ||
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Won't this flag foo-${boolean} and foo-${number} as possibly related? We still need to make sure the holes relate when this returns True, no?

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Yes, it'll flag them as possibly related. Or, rather, not flag them as definitely unrelated. We could potentially check the placeholders that immediately follow identical prefix texts or immediately precede identical suffix texts, but honestly there's very little gained from it. In fact, probably only the boolean vs. number disqualification. I think what is here already is sufficient, and it impacts whether we flag operands as non-overlapping, which isn't super critical to get 100% right.

sourceEnd.slice(sourceEnd.length - endLen) !== targetEnd.slice(targetEnd.length - endLen);
}

function isValidBigIntString(s: string): boolean {
const scanner = createScanner(ScriptTarget.ESNext, /*skipTrivia*/ false);
let success = true;
Expand Down Expand Up @@ -22449,7 +22463,7 @@ namespace ts {
if ((prop as TransientSymbol).isDiscriminantProperty === undefined) {
(prop as TransientSymbol).isDiscriminantProperty =
((prop as TransientSymbol).checkFlags & CheckFlags.Discriminant) === CheckFlags.Discriminant &&
!maybeTypeOfKind(getTypeOfSymbol(prop), TypeFlags.Instantiable & ~TypeFlags.TemplateLiteral);
!isGenericType(getTypeOfSymbol(prop));
}
return !!(prop as TransientSymbol).isDiscriminantProperty;
}
Expand Down Expand Up @@ -23008,15 +23022,17 @@ namespace ts {
return filterType(type, t => (t.flags & kind) !== 0);
}

// Return a new type in which occurrences of the string and number primitive types in
// typeWithPrimitives have been replaced with occurrences of string literals and numeric
// literals in typeWithLiterals, respectively.
// Return a new type in which occurrences of the string, number and bigint primitives and placeholder template
// literal types in typeWithPrimitives have been replaced with occurrences of compatible and more specific types
// from typeWithLiterals. This is essentially a limited form of intersection between the two types. We avoid a
// true intersection because it is more costly and, when applied to union types, generates a large number of
// types we don't actually care about.
function replacePrimitivesWithLiterals(typeWithPrimitives: Type, typeWithLiterals: Type) {
if (isTypeSubsetOf(stringType, typeWithPrimitives) && maybeTypeOfKind(typeWithLiterals, TypeFlags.StringLiteral) ||
isTypeSubsetOf(numberType, typeWithPrimitives) && maybeTypeOfKind(typeWithLiterals, TypeFlags.NumberLiteral) ||
isTypeSubsetOf(bigintType, typeWithPrimitives) && maybeTypeOfKind(typeWithLiterals, TypeFlags.BigIntLiteral)) {
if (maybeTypeOfKind(typeWithPrimitives, TypeFlags.String | TypeFlags.TemplateLiteral | TypeFlags.Number | TypeFlags.BigInt) &&
maybeTypeOfKind(typeWithLiterals, TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping | TypeFlags.NumberLiteral | TypeFlags.BigIntLiteral)) {
return mapType(typeWithPrimitives, t =>
t.flags & TypeFlags.String ? extractTypesOfKind(typeWithLiterals, TypeFlags.String | TypeFlags.StringLiteral) :
t.flags & TypeFlags.String ? extractTypesOfKind(typeWithLiterals, TypeFlags.String | TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) :
isPatternLiteralType(t) && !maybeTypeOfKind(typeWithLiterals, TypeFlags.String | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) ? extractTypesOfKind(typeWithLiterals, TypeFlags.StringLiteral) :
t.flags & TypeFlags.Number ? extractTypesOfKind(typeWithLiterals, TypeFlags.Number | TypeFlags.NumberLiteral) :
t.flags & TypeFlags.BigInt ? extractTypesOfKind(typeWithLiterals, TypeFlags.BigInt | TypeFlags.BigIntLiteral) : t);
}
Expand Down Expand Up @@ -23859,7 +23875,7 @@ namespace ts {
const narrowedPropType = narrowType(propType);
return filterType(type, t => {
const discriminantType = getTypeOfPropertyOrIndexSignature(t, propName);
return !(discriminantType.flags & TypeFlags.Never) && isTypeComparableTo(discriminantType, narrowedPropType);
return !(narrowedPropType.flags & TypeFlags.Never) && isTypeComparableTo(narrowedPropType, discriminantType);
});
}

Expand Down
43 changes: 42 additions & 1 deletion tests/baselines/reference/templateLiteralTypes3.errors.txt
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Expand Up @@ -5,9 +5,10 @@ tests/cases/conformance/types/literal/templateLiteralTypes3.ts(71,5): error TS23
tests/cases/conformance/types/literal/templateLiteralTypes3.ts(72,5): error TS2322: Type '`*${string}*`' is not assignable to type '`*${number}*`'.
tests/cases/conformance/types/literal/templateLiteralTypes3.ts(74,5): error TS2322: Type '"*false*" | "*true*"' is not assignable to type '`*${number}*`'.
Type '"*false*"' is not assignable to type '`*${number}*`'.
tests/cases/conformance/types/literal/templateLiteralTypes3.ts(133,9): error TS2367: This condition will always return 'false' since the types '`foo-${string}`' and '`baz-${string}`' have no overlap.


==== tests/cases/conformance/types/literal/templateLiteralTypes3.ts (6 errors) ====
==== tests/cases/conformance/types/literal/templateLiteralTypes3.ts (7 errors) ====
// Inference from template literal type to template literal type

type Foo1<T> = T extends `*${infer U}*` ? U : never;
Expand Down Expand Up @@ -146,4 +147,44 @@ tests/cases/conformance/types/literal/templateLiteralTypes3.ts(74,5): error TS23
declare function chain<F extends keyof Schema>(field: F | `${F}.${F}`): void;

chain("a");

// Repro from #46125

function ff1<T extends string>(x: `foo-${string}`, y: `${string}-bar`, z: `baz-${string}`) {
if (x === y) {
x; // `foo-${string}`
}
if (x === z) { // Error
~~~~~~~
!!! error TS2367: This condition will always return 'false' since the types '`foo-${string}`' and '`baz-${string}`' have no overlap.
}
}

function ff2(x: string, y: `foo-${string}` | 'bar') {
if (x === y) {
x; // `foo-${string}` | 'bar'
}
}

function ff3(x: string, y: `foo-${string}`) {
if (x === 'foo-test') {
x; // 'foo-test'
}
if (y === 'foo-test') {
y; // 'foo-test'
}
}

// Repro from #46045

export type Action =
| { type: `${string}_REQUEST` }
| { type: `${string}_SUCCESS`, response: string };

export function reducer(action: Action) {
if (action.type === 'FOO_SUCCESS') {
action.type;
action.response;
}
}

126 changes: 74 additions & 52 deletions tests/baselines/reference/templateLiteralTypes3.js
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Expand Up @@ -124,11 +124,51 @@ type Schema = { a: { b: { c: number } } };
declare function chain<F extends keyof Schema>(field: F | `${F}.${F}`): void;

chain("a");

// Repro from #46125

function ff1<T extends string>(x: `foo-${string}`, y: `${string}-bar`, z: `baz-${string}`) {
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Before I forget, can we also get a copy of this test with a signature like

function ff1<T extends string>(x: `foo-${T}`, y: `${T}-bar`, z: `baz-${T}`) {

? I figure it should behave the same, but, y'know, coverage. Maybe it can just be more cases on this signature, since it already has a generic parameter for some reason~

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Will do.

if (x === y) {
x; // `foo-${string}`
}
if (x === z) { // Error
}
}

function ff2(x: string, y: `foo-${string}` | 'bar') {
if (x === y) {
x; // `foo-${string}` | 'bar'
}
}

function ff3(x: string, y: `foo-${string}`) {
if (x === 'foo-test') {
x; // 'foo-test'
}
if (y === 'foo-test') {
y; // 'foo-test'
}
}

// Repro from #46045

export type Action =
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We probably want to remove the export from this and the other line to keep around the declaration emit in the test.

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Yeah, for sure.

| { type: `${string}_REQUEST` }
| { type: `${string}_SUCCESS`, response: string };

export function reducer(action: Action) {
if (action.type === 'FOO_SUCCESS') {
action.type;
action.response;
}
}


//// [templateLiteralTypes3.js]
"use strict";
// Inference from template literal type to template literal type
exports.__esModule = true;
exports.reducer = void 0;
function f1(s, n, b, t) {
var x1 = foo1('hello'); // Error
var x2 = foo1('*hello*');
Expand Down Expand Up @@ -177,59 +217,41 @@ var templated1 = value1 + " abc";
var value2 = "abc";
var templated2 = value2 + " abc";
chain("a");
// Repro from #46125
function ff1(x, y, z) {
if (x === y) {
x; // `foo-${string}`
}
if (x === z) { // Error
}
}
function ff2(x, y) {
if (x === y) {
x; // `foo-${string}` | 'bar'
}
}
function ff3(x, y) {
if (x === 'foo-test') {
x; // 'foo-test'
}
if (y === 'foo-test') {
y; // 'foo-test'
}
}
function reducer(action) {
if (action.type === 'FOO_SUCCESS') {
action.type;
action.response;
}
}
exports.reducer = reducer;


//// [templateLiteralTypes3.d.ts]
declare type Foo1<T> = T extends `*${infer U}*` ? U : never;
declare type T01 = Foo1<'hello'>;
declare type T02 = Foo1<'*hello*'>;
declare type T03 = Foo1<'**hello**'>;
declare type T04 = Foo1<`*${string}*`>;
declare type T05 = Foo1<`*${number}*`>;
declare type T06 = Foo1<`*${bigint}*`>;
declare type T07 = Foo1<`*${any}*`>;
declare type T08 = Foo1<`**${string}**`>;
declare type T09 = Foo1<`**${string}**${string}**`>;
declare type T10 = Foo1<`**${'a' | 'b' | 'c'}**`>;
declare type T11 = Foo1<`**${boolean}**${boolean}**`>;
declare function foo1<V extends string>(arg: `*${V}*`): V;
declare function f1<T extends string>(s: string, n: number, b: boolean, t: T): void;
declare type Parts<T> = T extends '' ? [] : T extends `${infer Head}${infer Tail}` ? [Head, ...Parts<Tail>] : never;
declare type T20 = Parts<`abc`>;
declare type T21 = Parts<`*${string}*`>;
declare type T22 = Parts<`*${number}*`>;
declare type T23 = Parts<`*${number}*${string}*${bigint}*`>;
declare function f2(): void;
declare function f3<T extends string>(s: string, n: number, b: boolean, t: T): void;
declare function f4<T extends number>(s: string, n: number, b: boolean, t: T): void;
declare type A<T> = T extends `${infer U}.${infer V}` ? U | V : never;
declare type B = A<`test.1024`>;
declare type C = A<`test.${number}`>;
declare type D<T> = T extends `${infer U}.${number}` ? U : never;
declare type E = D<`test.1024`>;
declare type F = D<`test.${number}`>;
declare type G<T> = T extends `${infer U}.${infer V}` ? U | V : never;
declare type H = G<`test.hoge`>;
declare type I = G<`test.${string}`>;
declare type J<T> = T extends `${infer U}.${string}` ? U : never;
declare type K = J<`test.hoge`>;
declare type L = J<`test.${string}`>;
declare type Templated = `${string} ${string}`;
declare const value1: string;
declare const templated1: Templated;
declare const value2 = "abc";
declare const templated2: Templated;
declare type Prefixes = "foo" | "bar";
declare type AllPrefixData = "foo:baz" | "bar:baz";
declare type PrefixData<P extends Prefixes> = `${P}:baz`;
interface ITest<P extends Prefixes, E extends AllPrefixData = PrefixData<P>> {
blah: string;
}
declare type Schema = {
a: {
b: {
c: number;
};
};
export declare type Action = {
type: `${string}_REQUEST`;
} | {
type: `${string}_SUCCESS`;
response: string;
};
declare function chain<F extends keyof Schema>(field: F | `${F}.${F}`): void;
export declare function reducer(action: Action): void;
89 changes: 89 additions & 0 deletions tests/baselines/reference/templateLiteralTypes3.symbols
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Expand Up @@ -405,3 +405,92 @@ declare function chain<F extends keyof Schema>(field: F | `${F}.${F}`): void;
chain("a");
>chain : Symbol(chain, Decl(templateLiteralTypes3.ts, 120, 42))

// Repro from #46125

function ff1<T extends string>(x: `foo-${string}`, y: `${string}-bar`, z: `baz-${string}`) {
>ff1 : Symbol(ff1, Decl(templateLiteralTypes3.ts, 124, 11))
>T : Symbol(T, Decl(templateLiteralTypes3.ts, 128, 13))
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 128, 31))
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 128, 50))
>z : Symbol(z, Decl(templateLiteralTypes3.ts, 128, 70))

if (x === y) {
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 128, 31))
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 128, 50))

x; // `foo-${string}`
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 128, 31))
}
if (x === z) { // Error
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 128, 31))
>z : Symbol(z, Decl(templateLiteralTypes3.ts, 128, 70))
}
}

function ff2(x: string, y: `foo-${string}` | 'bar') {
>ff2 : Symbol(ff2, Decl(templateLiteralTypes3.ts, 134, 1))
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 136, 13))
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 136, 23))

if (x === y) {
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 136, 13))
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 136, 23))

x; // `foo-${string}` | 'bar'
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 136, 13))
}
}

function ff3(x: string, y: `foo-${string}`) {
>ff3 : Symbol(ff3, Decl(templateLiteralTypes3.ts, 140, 1))
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 142, 13))
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 142, 23))

if (x === 'foo-test') {
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 142, 13))

x; // 'foo-test'
>x : Symbol(x, Decl(templateLiteralTypes3.ts, 142, 13))
}
if (y === 'foo-test') {
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 142, 23))

y; // 'foo-test'
>y : Symbol(y, Decl(templateLiteralTypes3.ts, 142, 23))
}
}

// Repro from #46045

export type Action =
>Action : Symbol(Action, Decl(templateLiteralTypes3.ts, 149, 1))

| { type: `${string}_REQUEST` }
>type : Symbol(type, Decl(templateLiteralTypes3.ts, 154, 7))

| { type: `${string}_SUCCESS`, response: string };
>type : Symbol(type, Decl(templateLiteralTypes3.ts, 155, 7))
>response : Symbol(response, Decl(templateLiteralTypes3.ts, 155, 34))

export function reducer(action: Action) {
>reducer : Symbol(reducer, Decl(templateLiteralTypes3.ts, 155, 54))
>action : Symbol(action, Decl(templateLiteralTypes3.ts, 157, 24))
>Action : Symbol(Action, Decl(templateLiteralTypes3.ts, 149, 1))

if (action.type === 'FOO_SUCCESS') {
>action.type : Symbol(type, Decl(templateLiteralTypes3.ts, 154, 7), Decl(templateLiteralTypes3.ts, 155, 7))
>action : Symbol(action, Decl(templateLiteralTypes3.ts, 157, 24))
>type : Symbol(type, Decl(templateLiteralTypes3.ts, 154, 7), Decl(templateLiteralTypes3.ts, 155, 7))

action.type;
>action.type : Symbol(type, Decl(templateLiteralTypes3.ts, 155, 7))
>action : Symbol(action, Decl(templateLiteralTypes3.ts, 157, 24))
>type : Symbol(type, Decl(templateLiteralTypes3.ts, 155, 7))

action.response;
>action.response : Symbol(response, Decl(templateLiteralTypes3.ts, 155, 34))
>action : Symbol(action, Decl(templateLiteralTypes3.ts, 157, 24))
>response : Symbol(response, Decl(templateLiteralTypes3.ts, 155, 34))
}
}

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