Use const context in intersections containing const type variables (#55779)

src/compiler/checker.ts

@@ -13912,7 +13912,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     function isConstTypeVariable(type: Type | undefined, depth = 0): boolean {
         return depth < 5 && !!(type && (
             type.flags & TypeFlags.TypeParameter && some((type as TypeParameter).symbol?.declarations, d => hasSyntacticModifier(d, ModifierFlags.Const)) ||
-            type.flags & TypeFlags.Union && some((type as UnionType).types, t => isConstTypeVariable(t, depth)) ||
+            type.flags & TypeFlags.UnionOrIntersection && some((type as UnionOrIntersectionType).types, t => isConstTypeVariable(t, depth)) ||
             type.flags & TypeFlags.IndexedAccess && isConstTypeVariable((type as IndexedAccessType).objectType, depth + 1) ||
             type.flags & TypeFlags.Conditional && isConstTypeVariable(getConstraintOfConditionalType(type as ConditionalType), depth + 1) ||
             type.flags & TypeFlags.Substitution && isConstTypeVariable((type as SubstitutionType).baseType, depth) ||

tests/baselines/reference/typeParameterConstModifiersWithIntersection.symbols

@@ -0,0 +1,56 @@
+//// [tests/cases/conformance/types/typeParameters/typeParameterLists/typeParameterConstModifiersWithIntersection.ts] ////
+
+=== typeParameterConstModifiersWithIntersection.ts ===
+// https://github.com/microsoft/TypeScript/issues/55778
+
+interface Config<T1 extends { type: string }> {
+>Config : Symbol(Config, Decl(typeParameterConstModifiersWithIntersection.ts, 0, 0))
+>T1 : Symbol(T1, Decl(typeParameterConstModifiersWithIntersection.ts, 2, 17))
+>type : Symbol(type, Decl(typeParameterConstModifiersWithIntersection.ts, 2, 29))
+
+  useIt: T1;
+>useIt : Symbol(Config.useIt, Decl(typeParameterConstModifiersWithIntersection.ts, 2, 47))
+>T1 : Symbol(T1, Decl(typeParameterConstModifiersWithIntersection.ts, 2, 17))
+}
+
+declare function test<
+>test : Symbol(test, Decl(typeParameterConstModifiersWithIntersection.ts, 4, 1))
+
+  T1 extends { type: string },
+>T1 : Symbol(T1, Decl(typeParameterConstModifiersWithIntersection.ts, 6, 22))
+>type : Symbol(type, Decl(typeParameterConstModifiersWithIntersection.ts, 7, 14))
+
+  const TConfig extends Config<T1>,
+>TConfig : Symbol(TConfig, Decl(typeParameterConstModifiersWithIntersection.ts, 7, 30))
+>Config : Symbol(Config, Decl(typeParameterConstModifiersWithIntersection.ts, 0, 0))
+>T1 : Symbol(T1, Decl(typeParameterConstModifiersWithIntersection.ts, 6, 22))
+
+>(config: { produceThing: T1 } & TConfig): TConfig;
+>config : Symbol(config, Decl(typeParameterConstModifiersWithIntersection.ts, 9, 2))
+>produceThing : Symbol(produceThing, Decl(typeParameterConstModifiersWithIntersection.ts, 9, 11))
+>T1 : Symbol(T1, Decl(typeParameterConstModifiersWithIntersection.ts, 6, 22))
+>TConfig : Symbol(TConfig, Decl(typeParameterConstModifiersWithIntersection.ts, 7, 30))
+>TConfig : Symbol(TConfig, Decl(typeParameterConstModifiersWithIntersection.ts, 7, 30))
+
+const result = test({
+>result : Symbol(result, Decl(typeParameterConstModifiersWithIntersection.ts, 11, 5))
+>test : Symbol(test, Decl(typeParameterConstModifiersWithIntersection.ts, 4, 1))
+
+  produceThing: {} as {
+>produceThing : Symbol(produceThing, Decl(typeParameterConstModifiersWithIntersection.ts, 11, 21))
+
+    type: "foo";
+>type : Symbol(type, Decl(typeParameterConstModifiersWithIntersection.ts, 12, 23))
+
+  },
+  useIt: {
+>useIt : Symbol(useIt, Decl(typeParameterConstModifiersWithIntersection.ts, 14, 4))
+
+    type: "foo",
+>type : Symbol(type, Decl(typeParameterConstModifiersWithIntersection.ts, 15, 10))
+
+  },
+  extra: 10,
+>extra : Symbol(extra, Decl(typeParameterConstModifiersWithIntersection.ts, 17, 4))
+
+});

tests/baselines/reference/typeParameterConstModifiersWithIntersection.types

@@ -0,0 +1,52 @@
+//// [tests/cases/conformance/types/typeParameters/typeParameterLists/typeParameterConstModifiersWithIntersection.ts] ////
+
+=== typeParameterConstModifiersWithIntersection.ts ===
+// https://github.com/microsoft/TypeScript/issues/55778
+
+interface Config<T1 extends { type: string }> {
+>type : string
+
+  useIt: T1;
+>useIt : T1
+}
+
+declare function test<
+>test : <T1 extends { type: string; }, const TConfig extends Config<T1>>(config: {    produceThing: T1;} & TConfig) => TConfig
+
+  T1 extends { type: string },
+>type : string
+
+  const TConfig extends Config<T1>,
+>(config: { produceThing: T1 } & TConfig): TConfig;
+>config : { produceThing: T1; } & TConfig
+>produceThing : T1
+
+const result = test({
+>result : { readonly produceThing: { type: "foo"; }; readonly useIt: { readonly type: "foo"; }; readonly extra: 10; }
+>test({  produceThing: {} as {    type: "foo";  },  useIt: {    type: "foo",  },  extra: 10,}) : { readonly produceThing: { type: "foo"; }; readonly useIt: { readonly type: "foo"; }; readonly extra: 10; }
+>test : <T1 extends { type: string; }, const TConfig extends Config<T1>>(config: { produceThing: T1; } & TConfig) => TConfig
+>{  produceThing: {} as {    type: "foo";  },  useIt: {    type: "foo",  },  extra: 10,} : { produceThing: { type: "foo"; }; useIt: { type: "foo"; }; extra: 10; }
+
+  produceThing: {} as {
+>produceThing : { type: "foo"; }
+>{} as {    type: "foo";  } : { type: "foo"; }
+>{} : {}
+
+    type: "foo";
+>type : "foo"
+
+  },
+  useIt: {
+>useIt : { type: "foo"; }
+>{    type: "foo",  } : { type: "foo"; }
+
+    type: "foo",
+>type : "foo"
+>"foo" : "foo"
+
+  },
+  extra: 10,
+>extra : 10
+>10 : 10
+
+});

tests/cases/conformance/types/typeParameters/typeParameterLists/typeParameterConstModifiersWithIntersection.ts

@@ -0,0 +1,23 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/TypeScript/issues/55778
+
+interface Config<T1 extends { type: string }> {
+  useIt: T1;
+}
+
+declare function test<
+  T1 extends { type: string },
+  const TConfig extends Config<T1>,
+>(config: { produceThing: T1 } & TConfig): TConfig;
+
+const result = test({
+  produceThing: {} as {
+    type: "foo";
+  },
+  useIt: {
+    type: "foo",
+  },
+  extra: 10,
+});