Template literal types for contextually typed template literal expressions

src/compiler/checker.ts

@@ -31799,7 +31799,12 @@ namespace ts {
                 texts.push(span.literal.text);
                 types.push(isTypeAssignableTo(type, templateConstraintType) ? type : stringType);
             }
-            return isConstContext(node) ? getTemplateLiteralType(texts, types) : stringType;
+            return isConstContext(node) || someType(getContextualType(node) || unknownType, isTemplateLiteralContextualType) ? getTemplateLiteralType(texts, types) : stringType;
+        }
+
+        function isTemplateLiteralContextualType(type: Type): boolean {
+            return !!(type.flags & (TypeFlags.StringLiteral | TypeFlags.TemplateLiteral) ||
+                type.flags & TypeFlags.InstantiableNonPrimitive && maybeTypeOfKind(getBaseConstraintOfType(type) || unknownType, TypeFlags.StringLike));
         }
 
         function getContextNode(node: Expression): Node {

tests/baselines/reference/stringLiteralTypesWithTemplateStrings02.errors.txt

@@ -1,12 +1,9 @@
 tests/cases/conformance/types/stringLiteral/stringLiteralTypesWithTemplateStrings02.ts(1,5): error TS2322: Type '"AB\nC"' is not assignable to type '"AB\r\nC"'.
-tests/cases/conformance/types/stringLiteral/stringLiteralTypesWithTemplateStrings02.ts(3,5): error TS2322: Type 'string' is not assignable to type '"DE\nF"'.
 
 
-==== tests/cases/conformance/types/stringLiteral/stringLiteralTypesWithTemplateStrings02.ts (2 errors) ====
+==== tests/cases/conformance/types/stringLiteral/stringLiteralTypesWithTemplateStrings02.ts (1 errors) ====
     let abc: "AB\r\nC" = `AB
         ~~~
 !!! error TS2322: Type '"AB\nC"' is not assignable to type '"AB\r\nC"'.
     C`;
-    let de_NEWLINE_f: "DE\nF" = `DE${"\n"}F`;
-        ~~~~~~~~~~~~
-!!! error TS2322: Type 'string' is not assignable to type '"DE\nF"'.
+    let de_NEWLINE_f: "DE\nF" = `DE${"\n"}F`;

tests/baselines/reference/stringLiteralTypesWithTemplateStrings02.types

@@ -6,6 +6,6 @@ let abc: "AB\r\nC" = `AB
 C`;
 let de_NEWLINE_f: "DE\nF" = `DE${"\n"}F`;
 >de_NEWLINE_f : "DE\nF"
->`DE${"\n"}F` : string
+>`DE${"\n"}F` : "DE\nF"
 >"\n" : "\n"
 

tests/baselines/reference/templateLiteralTypes1.types

@@ -8,7 +8,7 @@ const createScopedActionType = <S extends string>(scope: S) => <T extends string
 ><T extends string>(type: T) => `${scope}/${type}` as `${S}/${T}` : <T extends string>(type: T) => `${S}/${T}`
 >type : T
 >`${scope}/${type}` as `${S}/${T}` : `${S}/${T}`
->`${scope}/${type}` : string
+>`${scope}/${type}` : `${S}/${T}`
 >scope : S
 >type : T
 

tests/baselines/reference/templateLiteralTypes2.errors.txt

@@ -1,37 +1,22 @@
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(6,11): error TS2322: Type 'string' is not assignable to type '`abc${string}`'.
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(7,11): error TS2322: Type 'string' is not assignable to type '`abc${number}`'.
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(8,11): error TS2322: Type 'string' is not assignable to type '"abcfoo" | "abcbar" | "abcbaz"'.
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(9,11): error TS2322: Type 'string' is not assignable to type '`abc${T}`'.
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(21,11): error TS2322: Type 'string' is not assignable to type '`abc${string}`'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(23,11): error TS2322: Type 'string' is not assignable to type '`abc${string}`'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(29,11): error TS2322: Type 'string' is not assignable to type '`foo${string}` | `bar${string}`'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(32,11): error TS2322: Type 'string' is not assignable to type '`foo${string}` | `bar${string}` | `baz${string}`'.
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(43,11): error TS2322: Type 'string' is not assignable to type '`foo${string}`'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(67,9): error TS2322: Type '`foo${number}`' is not assignable to type 'String'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(68,9): error TS2322: Type '`foo${number}`' is not assignable to type 'Object'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(69,9): error TS2322: Type '`foo${number}`' is not assignable to type '{}'.
 tests/cases/conformance/types/literal/templateLiteralTypes2.ts(70,9): error TS2322: Type '`foo${number}`' is not assignable to type '{ length: number; }'.
-tests/cases/conformance/types/literal/templateLiteralTypes2.ts(98,7): error TS2322: Type 'string' is not assignable to type '`${number}px`'.
 
 
-==== tests/cases/conformance/types/literal/templateLiteralTypes2.ts (14 errors) ====
+==== tests/cases/conformance/types/literal/templateLiteralTypes2.ts (7 errors) ====
     function ft1<T extends string>(s: string, n: number, u: 'foo' | 'bar' | 'baz', t: T) {
         const c1 = `abc${s}`;  // `abc${string}`
         const c2 = `abc${n}`;  // `abc${number}`
         const c3 = `abc${u}`;  // "abcfoo" | "abcbar" | "abcbaz"
         const c4 = `abc${t}`;  // `abc${T}
         const d1: `abc${string}` = `abc${s}`;
-              ~~
-!!! error TS2322: Type 'string' is not assignable to type '`abc${string}`'.
         const d2: `abc${number}` = `abc${n}`;
-              ~~
-!!! error TS2322: Type 'string' is not assignable to type '`abc${number}`'.
         const d3: `abc${'foo' | 'bar' | 'baz'}` = `abc${u}`;
-              ~~
-!!! error TS2322: Type 'string' is not assignable to type '"abcfoo" | "abcbar" | "abcbaz"'.
         const d4: `abc${T}` = `abc${t}`;
-              ~~
-!!! error TS2322: Type 'string' is not assignable to type '`abc${T}`'.
     }
 
     function ft2(s: string) {
@@ -44,8 +29,6 @@ tests/cases/conformance/types/literal/templateLiteralTypes2.ts(98,7): error TS23
         const c2 = c1;  // Widening type `abc${string}`
         let v2 = c2;  // Type string
         const c3: `abc${string}` = `abc${s}`;
-              ~~
-!!! error TS2322: Type 'string' is not assignable to type '`abc${string}`'.
         let v3 = c3;  // Type `abc${string}`
         const c4: `abc${string}` = c1;  // Type `abc${string}`
               ~~
@@ -74,8 +57,6 @@ tests/cases/conformance/types/literal/templateLiteralTypes2.ts(98,7): error TS23
         const c1 = `foo${s}`;
         let v1 = c1;
         const c2: `foo${string}` = `foo${s}`;
-              ~~
-!!! error TS2322: Type 'string' is not assignable to type '`foo${string}`'.
         let v2 = c2;
         const c3 = `foo${s}` as `foo${string}`;
         let v3 = c3;
@@ -113,6 +94,14 @@ tests/cases/conformance/types/literal/templateLiteralTypes2.ts(98,7): error TS23
 !!! error TS2322: Type '`foo${number}`' is not assignable to type '{ length: number; }'.
     }
 
+    declare function g1<T>(x: T): T;
+    declare function g2<T extends string>(x: T): T;
+
+    function ft20(s: string) {
+        let x1 = g1(`xyz-${s}`);  // string
+        let x2 = g2(`xyz-${s}`);  // `xyz-${string}`
+    }
+
     // Repro from #41631
 
     declare function takesLiteral<T extends string>(literal: T): T extends `foo.bar.${infer R}` ? R : unknown;
@@ -139,6 +128,10 @@ tests/cases/conformance/types/literal/templateLiteralTypes2.ts(98,7): error TS23
     const pixelString: PixelValueType = `22px`;
 
     const pixelStringWithTemplate: PixelValueType = `${pixelValue}px`;
-          ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2322: Type 'string' is not assignable to type '`${number}px`'.
+
+    // Repro from #43143
+
+    function getCardTitle(title: string): `test-${string}` {
+        return `test-${title}`;
+    }
 

tests/baselines/reference/templateLiteralTypes2.js

@@ -71,6 +71,14 @@ function ft14(t: `foo${number}`) {
     let x6: { length: number } = t;
 }
 
+declare function g1<T>(x: T): T;
+declare function g2<T extends string>(x: T): T;
+
+function ft20(s: string) {
+    let x1 = g1(`xyz-${s}`);  // string
+    let x2 = g2(`xyz-${s}`);  // `xyz-${string}`
+}
+
 // Repro from #41631
 
 declare function takesLiteral<T extends string>(literal: T): T extends `foo.bar.${infer R}` ? R : unknown;
@@ -97,6 +105,12 @@ type PixelValueType = `${number}px`;
 const pixelString: PixelValueType = `22px`;
 
 const pixelStringWithTemplate: PixelValueType = `${pixelValue}px`;
+
+// Repro from #43143
+
+function getCardTitle(title: string): `test-${string}` {
+    return `test-${title}`;
+}
 
 
 //// [templateLiteralTypes2.js]
@@ -161,6 +175,10 @@ function ft14(t) {
     var x4 = t;
     var x6 = t;
 }
+function ft20(s) {
+    var x1 = g1("xyz-" + s); // string
+    var x2 = g2("xyz-" + s); // `xyz-${string}`
+}
 var t1 = takesLiteral("foo.bar.baz"); // "baz"
 var id2 = "foo.bar.baz";
 var t2 = takesLiteral(id2); // "baz"
@@ -172,6 +190,10 @@ var t5 = takesLiteral("foo.bar." + someUnion); // "abc" | "def" | "ghi"
 var pixelValue = 22;
 var pixelString = "22px";
 var pixelStringWithTemplate = pixelValue + "px";
+// Repro from #43143
+function getCardTitle(title) {
+    return "test-" + title;
+}
 
 
 //// [templateLiteralTypes2.d.ts]
@@ -185,17 +207,21 @@ declare function nonWidening<T extends string | number | symbol>(x: T): T;
 declare function ft13(s: string, cond: boolean): void;
 declare type T0 = string | `${number}px`;
 declare function ft14(t: `foo${number}`): void;
+declare function g1<T>(x: T): T;
+declare function g2<T extends string>(x: T): T;
+declare function ft20(s: string): void;
 declare function takesLiteral<T extends string>(literal: T): T extends `foo.bar.${infer R}` ? R : unknown;
 declare const t1: "baz";
 declare const id2 = "foo.bar.baz";
 declare const t2: "baz";
 declare const someString: string;
-declare const t3: unknown;
+declare const t3: string;
 declare const id4: string;
 declare const t4: unknown;
 declare const someUnion: 'abc' | 'def' | 'ghi';
-declare const t5: unknown;
+declare const t5: "abc" | "def" | "ghi";
 declare const pixelValue: number;
 declare type PixelValueType = `${number}px`;
 declare const pixelString: PixelValueType;
 declare const pixelStringWithTemplate: PixelValueType;
+declare function getCardTitle(title: string): `test-${string}`;

tests/baselines/reference/templateLiteralTypes2.symbols

@@ -257,68 +257,107 @@ function ft14(t: `foo${number}`) {
 >t : Symbol(t, Decl(templateLiteralTypes2.ts, 64, 14))
 }
 
+declare function g1<T>(x: T): T;
+>g1 : Symbol(g1, Decl(templateLiteralTypes2.ts, 70, 1))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 72, 20))
+>x : Symbol(x, Decl(templateLiteralTypes2.ts, 72, 23))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 72, 20))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 72, 20))
+
+declare function g2<T extends string>(x: T): T;
+>g2 : Symbol(g2, Decl(templateLiteralTypes2.ts, 72, 32))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 73, 20))
+>x : Symbol(x, Decl(templateLiteralTypes2.ts, 73, 38))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 73, 20))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 73, 20))
+
+function ft20(s: string) {
+>ft20 : Symbol(ft20, Decl(templateLiteralTypes2.ts, 73, 47))
+>s : Symbol(s, Decl(templateLiteralTypes2.ts, 75, 14))
+
+    let x1 = g1(`xyz-${s}`);  // string
+>x1 : Symbol(x1, Decl(templateLiteralTypes2.ts, 76, 7))
+>g1 : Symbol(g1, Decl(templateLiteralTypes2.ts, 70, 1))
+>s : Symbol(s, Decl(templateLiteralTypes2.ts, 75, 14))
+
+    let x2 = g2(`xyz-${s}`);  // `xyz-${string}`
+>x2 : Symbol(x2, Decl(templateLiteralTypes2.ts, 77, 7))
+>g2 : Symbol(g2, Decl(templateLiteralTypes2.ts, 72, 32))
+>s : Symbol(s, Decl(templateLiteralTypes2.ts, 75, 14))
+}
+
 // Repro from #41631
 
 declare function takesLiteral<T extends string>(literal: T): T extends `foo.bar.${infer R}` ? R : unknown;
->takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 70, 1))
->T : Symbol(T, Decl(templateLiteralTypes2.ts, 74, 30))
->literal : Symbol(literal, Decl(templateLiteralTypes2.ts, 74, 48))
->T : Symbol(T, Decl(templateLiteralTypes2.ts, 74, 30))
->T : Symbol(T, Decl(templateLiteralTypes2.ts, 74, 30))
->R : Symbol(R, Decl(templateLiteralTypes2.ts, 74, 87))
->R : Symbol(R, Decl(templateLiteralTypes2.ts, 74, 87))
+>takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 78, 1))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 82, 30))
+>literal : Symbol(literal, Decl(templateLiteralTypes2.ts, 82, 48))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 82, 30))
+>T : Symbol(T, Decl(templateLiteralTypes2.ts, 82, 30))
+>R : Symbol(R, Decl(templateLiteralTypes2.ts, 82, 87))
+>R : Symbol(R, Decl(templateLiteralTypes2.ts, 82, 87))
 
 const t1 = takesLiteral("foo.bar.baz"); // "baz"
->t1 : Symbol(t1, Decl(templateLiteralTypes2.ts, 76, 5))
->takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 70, 1))
+>t1 : Symbol(t1, Decl(templateLiteralTypes2.ts, 84, 5))
+>takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 78, 1))
 
 const id2 = "foo.bar.baz";
->id2 : Symbol(id2, Decl(templateLiteralTypes2.ts, 77, 5))
+>id2 : Symbol(id2, Decl(templateLiteralTypes2.ts, 85, 5))
 
 const t2 = takesLiteral(id2); // "baz"
->t2 : Symbol(t2, Decl(templateLiteralTypes2.ts, 78, 5))
->takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 70, 1))
->id2 : Symbol(id2, Decl(templateLiteralTypes2.ts, 77, 5))
+>t2 : Symbol(t2, Decl(templateLiteralTypes2.ts, 86, 5))
+>takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 78, 1))
+>id2 : Symbol(id2, Decl(templateLiteralTypes2.ts, 85, 5))
 
 declare const someString: string;
->someString : Symbol(someString, Decl(templateLiteralTypes2.ts, 80, 13))
+>someString : Symbol(someString, Decl(templateLiteralTypes2.ts, 88, 13))
 
 const t3 = takesLiteral(`foo.bar.${someString}`);  // string
->t3 : Symbol(t3, Decl(templateLiteralTypes2.ts, 81, 5))
->takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 70, 1))
->someString : Symbol(someString, Decl(templateLiteralTypes2.ts, 80, 13))
+>t3 : Symbol(t3, Decl(templateLiteralTypes2.ts, 89, 5))
+>takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 78, 1))
+>someString : Symbol(someString, Decl(templateLiteralTypes2.ts, 88, 13))
 
 const id4 = `foo.bar.${someString}`;
->id4 : Symbol(id4, Decl(templateLiteralTypes2.ts, 83, 5))
->someString : Symbol(someString, Decl(templateLiteralTypes2.ts, 80, 13))
+>id4 : Symbol(id4, Decl(templateLiteralTypes2.ts, 91, 5))
+>someString : Symbol(someString, Decl(templateLiteralTypes2.ts, 88, 13))
 
 const t4 = takesLiteral(id4);  // string
->t4 : Symbol(t4, Decl(templateLiteralTypes2.ts, 84, 5))
->takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 70, 1))
->id4 : Symbol(id4, Decl(templateLiteralTypes2.ts, 83, 5))
+>t4 : Symbol(t4, Decl(templateLiteralTypes2.ts, 92, 5))
+>takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 78, 1))
+>id4 : Symbol(id4, Decl(templateLiteralTypes2.ts, 91, 5))
 
 declare const someUnion: 'abc' | 'def' | 'ghi';
->someUnion : Symbol(someUnion, Decl(templateLiteralTypes2.ts, 86, 13))
+>someUnion : Symbol(someUnion, Decl(templateLiteralTypes2.ts, 94, 13))
 
 const t5 = takesLiteral(`foo.bar.${someUnion}`);  // "abc" | "def" | "ghi"
->t5 : Symbol(t5, Decl(templateLiteralTypes2.ts, 87, 5))
->takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 70, 1))
->someUnion : Symbol(someUnion, Decl(templateLiteralTypes2.ts, 86, 13))
+>t5 : Symbol(t5, Decl(templateLiteralTypes2.ts, 95, 5))
+>takesLiteral : Symbol(takesLiteral, Decl(templateLiteralTypes2.ts, 78, 1))
+>someUnion : Symbol(someUnion, Decl(templateLiteralTypes2.ts, 94, 13))
 
 // Repro from #41732
 
 const pixelValue: number = 22;
->pixelValue : Symbol(pixelValue, Decl(templateLiteralTypes2.ts, 91, 5))
+>pixelValue : Symbol(pixelValue, Decl(templateLiteralTypes2.ts, 99, 5))
 
 type PixelValueType = `${number}px`;
->PixelValueType : Symbol(PixelValueType, Decl(templateLiteralTypes2.ts, 91, 30))
+>PixelValueType : Symbol(PixelValueType, Decl(templateLiteralTypes2.ts, 99, 30))
 
 const pixelString: PixelValueType = `22px`;
->pixelString : Symbol(pixelString, Decl(templateLiteralTypes2.ts, 95, 5))
->PixelValueType : Symbol(PixelValueType, Decl(templateLiteralTypes2.ts, 91, 30))
+>pixelString : Symbol(pixelString, Decl(templateLiteralTypes2.ts, 103, 5))
+>PixelValueType : Symbol(PixelValueType, Decl(templateLiteralTypes2.ts, 99, 30))
 
 const pixelStringWithTemplate: PixelValueType = `${pixelValue}px`;
->pixelStringWithTemplate : Symbol(pixelStringWithTemplate, Decl(templateLiteralTypes2.ts, 97, 5))
->PixelValueType : Symbol(PixelValueType, Decl(templateLiteralTypes2.ts, 91, 30))
->pixelValue : Symbol(pixelValue, Decl(templateLiteralTypes2.ts, 91, 5))
+>pixelStringWithTemplate : Symbol(pixelStringWithTemplate, Decl(templateLiteralTypes2.ts, 105, 5))
+>PixelValueType : Symbol(PixelValueType, Decl(templateLiteralTypes2.ts, 99, 30))
+>pixelValue : Symbol(pixelValue, Decl(templateLiteralTypes2.ts, 99, 5))
+
+// Repro from #43143
+
+function getCardTitle(title: string): `test-${string}` {
+>getCardTitle : Symbol(getCardTitle, Decl(templateLiteralTypes2.ts, 105, 66))
+>title : Symbol(title, Decl(templateLiteralTypes2.ts, 109, 22))
+
+    return `test-${title}`;
+>title : Symbol(title, Decl(templateLiteralTypes2.ts, 109, 22))
+}