Merge pull request #19697 from Microsoft/fixFreshLiteralsInIntersections

Fix fresh literals in intersections

Author: ahejlsberg

src/compiler/checker.ts

@@ -7592,11 +7592,11 @@ namespace ts {
             }
         }
 
-        // Add the given types to the given type set. Order is preserved, duplicates are removed,
-        // and nested types of the given kind are flattened into the set.
+        // Add the given types to the given type set. Order is preserved, freshness is removed from literal
+        // types, duplicates are removed, and nested types of the given kind are flattened into the set.
         function addTypesToIntersection(typeSet: TypeSet, types: Type[]) {
             for (const type of types) {
-                addTypeToIntersection(typeSet, type);
+                addTypeToIntersection(typeSet, getRegularTypeOfLiteralType(type));
             }
         }
 

tests/baselines/reference/freshLiteralTypesInIntersections.js

@@ -0,0 +1,13 @@
+//// [freshLiteralTypesInIntersections.ts]
+// Repro from #19657
+
+declare function func<A extends string, B extends A>(a: A, b: B[]): (ab: A & B) => void;
+const q = func("x" as "x" | "y", ["x"]);
+q("x");
+
+
+//// [freshLiteralTypesInIntersections.js]
+"use strict";
+// Repro from #19657
+var q = func("x", ["x"]);
+q("x");

tests/baselines/reference/freshLiteralTypesInIntersections.symbols

@@ -0,0 +1,23 @@
+=== tests/cases/compiler/freshLiteralTypesInIntersections.ts ===
+// Repro from #19657
+
+declare function func<A extends string, B extends A>(a: A, b: B[]): (ab: A & B) => void;
+>func : Symbol(func, Decl(freshLiteralTypesInIntersections.ts, 0, 0))
+>A : Symbol(A, Decl(freshLiteralTypesInIntersections.ts, 2, 22))
+>B : Symbol(B, Decl(freshLiteralTypesInIntersections.ts, 2, 39))
+>A : Symbol(A, Decl(freshLiteralTypesInIntersections.ts, 2, 22))
+>a : Symbol(a, Decl(freshLiteralTypesInIntersections.ts, 2, 53))
+>A : Symbol(A, Decl(freshLiteralTypesInIntersections.ts, 2, 22))
+>b : Symbol(b, Decl(freshLiteralTypesInIntersections.ts, 2, 58))
+>B : Symbol(B, Decl(freshLiteralTypesInIntersections.ts, 2, 39))
+>ab : Symbol(ab, Decl(freshLiteralTypesInIntersections.ts, 2, 69))
+>A : Symbol(A, Decl(freshLiteralTypesInIntersections.ts, 2, 22))
+>B : Symbol(B, Decl(freshLiteralTypesInIntersections.ts, 2, 39))
+
+const q = func("x" as "x" | "y", ["x"]);
+>q : Symbol(q, Decl(freshLiteralTypesInIntersections.ts, 3, 5))
+>func : Symbol(func, Decl(freshLiteralTypesInIntersections.ts, 0, 0))
+
+q("x");
+>q : Symbol(q, Decl(freshLiteralTypesInIntersections.ts, 3, 5))
+

tests/baselines/reference/freshLiteralTypesInIntersections.types

@@ -0,0 +1,30 @@
+=== tests/cases/compiler/freshLiteralTypesInIntersections.ts ===
+// Repro from #19657
+
+declare function func<A extends string, B extends A>(a: A, b: B[]): (ab: A & B) => void;
+>func : <A extends string, B extends A>(a: A, b: B[]) => (ab: A & B) => void
+>A : A
+>B : B
+>A : A
+>a : A
+>A : A
+>b : B[]
+>B : B
+>ab : A & B
+>A : A
+>B : B
+
+const q = func("x" as "x" | "y", ["x"]);
+>q : (ab: "x") => void
+>func("x" as "x" | "y", ["x"]) : (ab: "x") => void
+>func : <A extends string, B extends A>(a: A, b: B[]) => (ab: A & B) => void
+>"x" as "x" | "y" : "x" | "y"
+>"x" : "x"
+>["x"] : "x"[]
+>"x" : "x"
+
+q("x");
+>q("x") : void
+>q : (ab: "x") => void
+>"x" : "x"
+

tests/cases/compiler/freshLiteralTypesInIntersections.ts

@@ -0,0 +1,7 @@
+// @strict: true
+
+// Repro from #19657
+
+declare function func<A extends string, B extends A>(a: A, b: B[]): (ab: A & B) => void;
+const q = func("x" as "x" | "y", ["x"]);
+q("x");