Properly instantiate object types created from rest parameters (#34826)

* Anonymous types of rest variable declarations need instantiation

* Add regression test

* Accept new baselines

* Accept new API baselines

Author: ahejlsberg

src/compiler/checker.ts

@@ -6657,7 +6657,9 @@ namespace ts {
             }
             const stringIndexInfo = getIndexInfoOfType(source, IndexKind.String);
             const numberIndexInfo = getIndexInfoOfType(source, IndexKind.Number);
-            return createAnonymousType(symbol, members, emptyArray, emptyArray, stringIndexInfo, numberIndexInfo);
+            const result = createAnonymousType(symbol, members, emptyArray, emptyArray, stringIndexInfo, numberIndexInfo);
+            result.objectFlags |= ObjectFlags.ObjectRestType;
+            return result;
         }
 
         // Determine the control flow type associated with a destructuring declaration or assignment. The following
@@ -17240,7 +17242,7 @@ namespace ts {
             return !!(type.flags & TypeFlags.Instantiable ||
                 objectFlags & ObjectFlags.Reference && ((<TypeReference>type).node || forEach(getTypeArguments(<TypeReference>type), couldContainTypeVariables)) ||
                 objectFlags & ObjectFlags.Anonymous && type.symbol && type.symbol.flags & (SymbolFlags.Function | SymbolFlags.Method | SymbolFlags.Class | SymbolFlags.TypeLiteral | SymbolFlags.ObjectLiteral) && type.symbol.declarations ||
-                objectFlags & ObjectFlags.Mapped ||
+                objectFlags & (ObjectFlags.Mapped | ObjectFlags.ObjectRestType) ||
                 type.flags & TypeFlags.UnionOrIntersection && !(type.flags & TypeFlags.EnumLiteral) && couldUnionOrIntersectionContainTypeVariables(<UnionOrIntersectionType>type));
         }
 

src/compiler/types.ts

@@ -4352,14 +4352,15 @@ namespace ts {
         JSLiteral        = 1 << 14, // Object type declared in JS - disables errors on read/write of nonexisting members
         FreshLiteral     = 1 << 15, // Fresh object literal
         ArrayLiteral     = 1 << 16, // Originates in an array literal
+        ObjectRestType   = 1 << 17, // Originates in object rest declaration
         /* @internal */
-        PrimitiveUnion   = 1 << 17, // Union of only primitive types
+        PrimitiveUnion   = 1 << 18, // Union of only primitive types
         /* @internal */
-        ContainsWideningType = 1 << 18, // Type is or contains undefined or null widening type
+        ContainsWideningType = 1 << 19, // Type is or contains undefined or null widening type
         /* @internal */
-        ContainsObjectOrArrayLiteral = 1 << 19, // Type is or contains object literal type
+        ContainsObjectOrArrayLiteral = 1 << 20, // Type is or contains object literal type
         /* @internal */
-        NonInferrableType = 1 << 20, // Type is or contains anyFunctionType or silentNeverType
+        NonInferrableType = 1 << 21, // Type is or contains anyFunctionType or silentNeverType
         ClassOrInterface = Class | Interface,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectOrArrayLiteral,

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2378,6 +2378,7 @@ declare namespace ts {
         JSLiteral = 16384,
         FreshLiteral = 32768,
         ArrayLiteral = 65536,
+        ObjectRestType = 131072,
         ClassOrInterface = 3,
     }
     export interface ObjectType extends Type {

tests/baselines/reference/api/typescript.d.ts

@@ -2378,6 +2378,7 @@ declare namespace ts {
         JSLiteral = 16384,
         FreshLiteral = 32768,
         ArrayLiteral = 65536,
+        ObjectRestType = 131072,
         ClassOrInterface = 3,
     }
     export interface ObjectType extends Type {

tests/baselines/reference/restParameterTypeInstantiation.js

@@ -0,0 +1,34 @@
+//// [restParameterTypeInstantiation.ts]
+// Repro from #33823
+
+interface TestGeneric<TG> {
+  f: string
+  g: TG
+}
+
+const removeF = <TX>({ f, ...rest }: TestGeneric<TX>) => {
+  return rest
+}
+
+const result: number = removeF<number>({ f: '', g: 3 }).g
+
+
+//// [restParameterTypeInstantiation.js]
+"use strict";
+// Repro from #33823
+var __rest = (this && this.__rest) || function (s, e) {
+    var t = {};
+    for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)
+        t[p] = s[p];
+    if (s != null && typeof Object.getOwnPropertySymbols === "function")
+        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) {
+            if (e.indexOf(p[i]) < 0 && Object.prototype.propertyIsEnumerable.call(s, p[i]))
+                t[p[i]] = s[p[i]];
+        }
+    return t;
+};
+var removeF = function (_a) {
+    var f = _a.f, rest = __rest(_a, ["f"]);
+    return rest;
+};
+var result = removeF({ f: '', g: 3 }).g;

tests/baselines/reference/restParameterTypeInstantiation.symbols

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/restParameterTypeInstantiation.ts ===
+// Repro from #33823
+
+interface TestGeneric<TG> {
+>TestGeneric : Symbol(TestGeneric, Decl(restParameterTypeInstantiation.ts, 0, 0))
+>TG : Symbol(TG, Decl(restParameterTypeInstantiation.ts, 2, 22))
+
+  f: string
+>f : Symbol(TestGeneric.f, Decl(restParameterTypeInstantiation.ts, 2, 27))
+
+  g: TG
+>g : Symbol(TestGeneric.g, Decl(restParameterTypeInstantiation.ts, 3, 11))
+>TG : Symbol(TG, Decl(restParameterTypeInstantiation.ts, 2, 22))
+}
+
+const removeF = <TX>({ f, ...rest }: TestGeneric<TX>) => {
+>removeF : Symbol(removeF, Decl(restParameterTypeInstantiation.ts, 7, 5))
+>TX : Symbol(TX, Decl(restParameterTypeInstantiation.ts, 7, 17))
+>f : Symbol(f, Decl(restParameterTypeInstantiation.ts, 7, 22))
+>rest : Symbol(rest, Decl(restParameterTypeInstantiation.ts, 7, 25))
+>TestGeneric : Symbol(TestGeneric, Decl(restParameterTypeInstantiation.ts, 0, 0))
+>TX : Symbol(TX, Decl(restParameterTypeInstantiation.ts, 7, 17))
+
+  return rest
+>rest : Symbol(rest, Decl(restParameterTypeInstantiation.ts, 7, 25))
+}
+
+const result: number = removeF<number>({ f: '', g: 3 }).g
+>result : Symbol(result, Decl(restParameterTypeInstantiation.ts, 11, 5))
+>removeF<number>({ f: '', g: 3 }).g : Symbol(TestGeneric.g, Decl(restParameterTypeInstantiation.ts, 3, 11))
+>removeF : Symbol(removeF, Decl(restParameterTypeInstantiation.ts, 7, 5))
+>f : Symbol(f, Decl(restParameterTypeInstantiation.ts, 11, 40))
+>g : Symbol(g, Decl(restParameterTypeInstantiation.ts, 11, 47))
+>g : Symbol(TestGeneric.g, Decl(restParameterTypeInstantiation.ts, 3, 11))
+

tests/baselines/reference/restParameterTypeInstantiation.types

@@ -0,0 +1,33 @@
+=== tests/cases/compiler/restParameterTypeInstantiation.ts ===
+// Repro from #33823
+
+interface TestGeneric<TG> {
+  f: string
+>f : string
+
+  g: TG
+>g : TG
+}
+
+const removeF = <TX>({ f, ...rest }: TestGeneric<TX>) => {
+>removeF : <TX>({ f, ...rest }: TestGeneric<TX>) => { g: TX; }
+><TX>({ f, ...rest }: TestGeneric<TX>) => {  return rest} : <TX>({ f, ...rest }: TestGeneric<TX>) => { g: TX; }
+>f : string
+>rest : { g: TX; }
+
+  return rest
+>rest : { g: TX; }
+}
+
+const result: number = removeF<number>({ f: '', g: 3 }).g
+>result : number
+>removeF<number>({ f: '', g: 3 }).g : number
+>removeF<number>({ f: '', g: 3 }) : { g: number; }
+>removeF : <TX>({ f, ...rest }: TestGeneric<TX>) => { g: TX; }
+>{ f: '', g: 3 } : { f: string; g: number; }
+>f : string
+>'' : ""
+>g : number
+>3 : 3
+>g : number
+

tests/cases/compiler/restParameterTypeInstantiation.ts

@@ -0,0 +1,14 @@
+// @strict: true
+
+// Repro from #33823
+
+interface TestGeneric<TG> {
+  f: string
+  g: TG
+}
+
+const removeF = <TX>({ f, ...rest }: TestGeneric<TX>) => {
+  return rest
+}
+
+const result: number = removeF<number>({ f: '', g: 3 }).g