Fix caching of union constituent instantiations that share a declaration

src/compiler/checker.ts

@@ -15073,7 +15073,6 @@ namespace ts {
                 links.outerTypeParameters = typeParameters;
                 if (typeParameters.length) {
                     links.instantiations = new Map<string, Type>();
-                    links.instantiations.set(getTypeListId(typeParameters), target);
                 }
             }
             if (typeParameters.length) {
@@ -15083,6 +15082,10 @@ namespace ts {
                 const combinedMapper = combineTypeMappers(type.mapper, mapper);
                 const typeArguments = map(typeParameters, t => getMappedType(t, combinedMapper));
                 const id = getTypeListId(typeArguments);
+                if (id === getTypeListId(typeParameters)) {
+                    return target;
+                }
+
                 let result = links.instantiations!.get(id);
                 if (!result) {
                     const newMapper = createTypeMapper(typeParameters, typeArguments);

tests/baselines/reference/objectInstantiationFromUnionSpread.js

@@ -0,0 +1,41 @@
+//// [objectInstantiationFromUnionSpread.ts]
+// #40995
+
+interface Success {
+  isSuccess: true;
+}
+
+interface Fail {
+  isSuccess: false;
+}
+
+type Item = Success | Fail;
+
+function f1(a: Item[]) {
+  a.map(item => ({ ...item })).filter(value => {});
+}
+
+function f2<T>(a: Item[]) {
+  a.map(item => ({ ...item })).filter(value => {});
+}
+
+
+//// [objectInstantiationFromUnionSpread.js]
+// #40995
+var __assign = (this && this.__assign) || function () {
+    __assign = Object.assign || function(t) {
+        for (var s, i = 1, n = arguments.length; i < n; i++) {
+            s = arguments[i];
+            for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p))
+                t[p] = s[p];
+        }
+        return t;
+    };
+    return __assign.apply(this, arguments);
+};
+function f1(a) {
+    a.map(function (item) { return (__assign({}, item)); }).filter(function (value) { });
+}
+function f2(a) {
+    a.map(function (item) { return (__assign({}, item)); }).filter(function (value) { });
+}

tests/baselines/reference/objectInstantiationFromUnionSpread.symbols

@@ -0,0 +1,55 @@
+=== tests/cases/compiler/objectInstantiationFromUnionSpread.ts ===
+// #40995
+
+interface Success {
+>Success : Symbol(Success, Decl(objectInstantiationFromUnionSpread.ts, 0, 0))
+
+  isSuccess: true;
+>isSuccess : Symbol(Success.isSuccess, Decl(objectInstantiationFromUnionSpread.ts, 2, 19))
+}
+
+interface Fail {
+>Fail : Symbol(Fail, Decl(objectInstantiationFromUnionSpread.ts, 4, 1))
+
+  isSuccess: false;
+>isSuccess : Symbol(Fail.isSuccess, Decl(objectInstantiationFromUnionSpread.ts, 6, 16))
+}
+
+type Item = Success | Fail;
+>Item : Symbol(Item, Decl(objectInstantiationFromUnionSpread.ts, 8, 1))
+>Success : Symbol(Success, Decl(objectInstantiationFromUnionSpread.ts, 0, 0))
+>Fail : Symbol(Fail, Decl(objectInstantiationFromUnionSpread.ts, 4, 1))
+
+function f1(a: Item[]) {
+>f1 : Symbol(f1, Decl(objectInstantiationFromUnionSpread.ts, 10, 27))
+>a : Symbol(a, Decl(objectInstantiationFromUnionSpread.ts, 12, 12))
+>Item : Symbol(Item, Decl(objectInstantiationFromUnionSpread.ts, 8, 1))
+
+  a.map(item => ({ ...item })).filter(value => {});
+>a.map(item => ({ ...item })).filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>a.map : Symbol(Array.map, Decl(lib.es5.d.ts, --, --))
+>a : Symbol(a, Decl(objectInstantiationFromUnionSpread.ts, 12, 12))
+>map : Symbol(Array.map, Decl(lib.es5.d.ts, --, --))
+>item : Symbol(item, Decl(objectInstantiationFromUnionSpread.ts, 13, 8))
+>item : Symbol(item, Decl(objectInstantiationFromUnionSpread.ts, 13, 8))
+>filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>value : Symbol(value, Decl(objectInstantiationFromUnionSpread.ts, 13, 38))
+}
+
+function f2<T>(a: Item[]) {
+>f2 : Symbol(f2, Decl(objectInstantiationFromUnionSpread.ts, 14, 1))
+>T : Symbol(T, Decl(objectInstantiationFromUnionSpread.ts, 16, 12))
+>a : Symbol(a, Decl(objectInstantiationFromUnionSpread.ts, 16, 15))
+>Item : Symbol(Item, Decl(objectInstantiationFromUnionSpread.ts, 8, 1))
+
+  a.map(item => ({ ...item })).filter(value => {});
+>a.map(item => ({ ...item })).filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>a.map : Symbol(Array.map, Decl(lib.es5.d.ts, --, --))
+>a : Symbol(a, Decl(objectInstantiationFromUnionSpread.ts, 16, 15))
+>map : Symbol(Array.map, Decl(lib.es5.d.ts, --, --))
+>item : Symbol(item, Decl(objectInstantiationFromUnionSpread.ts, 17, 8))
+>item : Symbol(item, Decl(objectInstantiationFromUnionSpread.ts, 17, 8))
+>filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>value : Symbol(value, Decl(objectInstantiationFromUnionSpread.ts, 17, 38))
+}
+

tests/baselines/reference/objectInstantiationFromUnionSpread.types

@@ -0,0 +1,60 @@
+=== tests/cases/compiler/objectInstantiationFromUnionSpread.ts ===
+// #40995
+
+interface Success {
+  isSuccess: true;
+>isSuccess : true
+>true : true
+}
+
+interface Fail {
+  isSuccess: false;
+>isSuccess : false
+>false : false
+}
+
+type Item = Success | Fail;
+>Item : Item
+
+function f1(a: Item[]) {
+>f1 : (a: Item[]) => void
+>a : Item[]
+
+  a.map(item => ({ ...item })).filter(value => {});
+>a.map(item => ({ ...item })).filter(value => {}) : ({ isSuccess: true; } | { isSuccess: false; })[]
+>a.map(item => ({ ...item })).filter : { <S extends { isSuccess: true; } | { isSuccess: false; }>(predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => value is S, thisArg?: any): S[]; (predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => unknown, thisArg?: any): ({ isSuccess: true; } | { isSuccess: false; })[]; }
+>a.map(item => ({ ...item })) : ({ isSuccess: true; } | { isSuccess: false; })[]
+>a.map : <U>(callbackfn: (value: Item, index: number, array: Item[]) => U, thisArg?: any) => U[]
+>a : Item[]
+>map : <U>(callbackfn: (value: Item, index: number, array: Item[]) => U, thisArg?: any) => U[]
+>item => ({ ...item }) : (item: Item) => { isSuccess: true; } | { isSuccess: false; }
+>item : Item
+>({ ...item }) : { isSuccess: true; } | { isSuccess: false; }
+>{ ...item } : { isSuccess: true; } | { isSuccess: false; }
+>item : Item
+>filter : { <S extends { isSuccess: true; } | { isSuccess: false; }>(predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => value is S, thisArg?: any): S[]; (predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => unknown, thisArg?: any): ({ isSuccess: true; } | { isSuccess: false; })[]; }
+>value => {} : (value: { isSuccess: true; } | { isSuccess: false; }) => void
+>value : { isSuccess: true; } | { isSuccess: false; }
+}
+
+function f2<T>(a: Item[]) {
+>f2 : <T>(a: Item[]) => void
+>a : Item[]
+
+  a.map(item => ({ ...item })).filter(value => {});
+>a.map(item => ({ ...item })).filter(value => {}) : ({ isSuccess: true; } | { isSuccess: false; })[]
+>a.map(item => ({ ...item })).filter : { <S extends { isSuccess: true; } | { isSuccess: false; }>(predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => value is S, thisArg?: any): S[]; (predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => unknown, thisArg?: any): ({ isSuccess: true; } | { isSuccess: false; })[]; }
+>a.map(item => ({ ...item })) : ({ isSuccess: true; } | { isSuccess: false; })[]
+>a.map : <U>(callbackfn: (value: Item, index: number, array: Item[]) => U, thisArg?: any) => U[]
+>a : Item[]
+>map : <U>(callbackfn: (value: Item, index: number, array: Item[]) => U, thisArg?: any) => U[]
+>item => ({ ...item }) : (item: Item) => { isSuccess: true; } | { isSuccess: false; }
+>item : Item
+>({ ...item }) : { isSuccess: true; } | { isSuccess: false; }
+>{ ...item } : { isSuccess: true; } | { isSuccess: false; }
+>item : Item
+>filter : { <S extends { isSuccess: true; } | { isSuccess: false; }>(predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => value is S, thisArg?: any): S[]; (predicate: (value: { isSuccess: true; } | { isSuccess: false; }, index: number, array: ({ isSuccess: true; } | { isSuccess: false; })[]) => unknown, thisArg?: any): ({ isSuccess: true; } | { isSuccess: false; })[]; }
+>value => {} : (value: { isSuccess: true; } | { isSuccess: false; }) => void
+>value : { isSuccess: true; } | { isSuccess: false; }
+}
+

tests/cases/compiler/objectInstantiationFromUnionSpread.ts

@@ -0,0 +1,21 @@
+// @strictFunctionTypes: true
+
+// #40995
+
+interface Success {
+  isSuccess: true;
+}
+
+interface Fail {
+  isSuccess: false;
+}
+
+type Item = Success | Fail;
+
+function f1(a: Item[]) {
+  a.map(item => ({ ...item })).filter(value => {});
+}
+
+function f2<T>(a: Item[]) {
+  a.map(item => ({ ...item })).filter(value => {});
+}