Do not materialize optional undefined properties inside actual types

src/compiler/types.ts

@@ -3890,7 +3890,9 @@ namespace ts {
         /* @internal */
         EmptyObject = ContainsAnyFunctionType,
         /* @internal */
-        ConstructionFlags = NonWideningType | Wildcard | EmptyObject,
+        AllFresh = EnumLiteral,
+        /* @internal */
+        ConstructionFlags = NonWideningType | Wildcard | EmptyObject | AllFresh,
         // The following flag is used for different purposes by maybeTypeOfKind
         /* @internal */
         GenericMappedType = ContainsWideningType
@@ -3988,6 +3990,8 @@ namespace ts {
         /* @internal */ constructSignatures?: ReadonlyArray<Signature>; // Construct signatures of type
         /* @internal */ stringIndexInfo?: IndexInfo;      // String indexing info
         /* @internal */ numberIndexInfo?: IndexInfo;      // Numeric indexing info
+        /* @internal */ regularType?: this;
+        /* @internal */ freshType?: this;
     }
 
     /** Class and interface types (ObjectFlags.Class and ObjectFlags.Interface). */
@@ -4071,9 +4075,22 @@ namespace ts {
         couldContainTypeVariables: boolean;
     }
 
+    /* @internal */
+    export const enum UnionFlags {
+        PrimitiveOnly           = 1 << 0,
+        FreshObjectsOnly        = 1 << 1,
+        WidenedFreshObjectsOnly = 1 << 2,
+    }
+
     export interface UnionType extends UnionOrIntersectionType {
         /* @internal */
-        primitiveTypesOnly: boolean;
+        unionFlags: UnionFlags;
+        /* @internal */
+        propertyNameCache?: UnderscoreEscapedMap<true>;       // Cache of possible property names
+        /* @internal */
+        freshType?: this; // Pointer back to the original `FreshObjectsOnly` union for `WidenedFreshObjectsOnly` unions
+        /* @internal */
+        regularType?: this; // Pointer to the widened union for `FreshObjectsOnly` unions, if it has been made
     }
 
     export interface IntersectionType extends UnionOrIntersectionType {
@@ -4122,14 +4139,6 @@ namespace ts {
         constructSignatures: ReadonlyArray<Signature>; // Construct signatures of type
     }
 
-    /* @internal */
-    // Object literals are initially marked fresh. Freshness disappears following an assignment,
-    // before a type assertion, or when an object literal's type is widened. The regular
-    // version of a fresh type is identical except for the TypeFlags.FreshObjectLiteral flag.
-    export interface FreshObjectLiteralType extends ResolvedType {
-        regularType: ResolvedType;  // Regular version of fresh type
-    }
-
     // Just a place to cache element types of iterables and iterators
     /* @internal */
     export interface IterableOrIteratorType extends ObjectType, UnionType {

src/compiler/utilities.ts

@@ -20,6 +20,7 @@ namespace ts {
     export const externalHelpersModuleNameText = "tslib";
 
     export const defaultMaximumTruncationLength = 160;
+    export const defaultHardCapTrunctionLength = 100000; // Trunction limit used even when `noErrorTruncation` is on to avoid OOM when printing huge types
 
     export function getDeclarationOfKind<T extends Declaration>(symbol: Symbol, kind: T["kind"]): T | undefined {
         const declarations = symbol.declarations;

src/harness/harness.ts

@@ -1107,7 +1107,8 @@ namespace Harness {
             { name: "symlink", type: "string" },
             { name: "link", type: "string" },
             // Emitted js baseline will print full paths for every output file
-            { name: "fullEmitPaths", type: "boolean" }
+            { name: "fullEmitPaths", type: "boolean" },
+            { name: "skipTypeAndSymbol", type: "boolean" }
         ];
 
         let optionsIndex: ts.Map<ts.CommandLineOption>;

src/testRunner/compilerRunner.ts

@@ -246,6 +246,9 @@ class CompilerTest {
     }
 
     public verifyTypesAndSymbols() {
+        if (this.harnessSettings.skipTypeAndSymbol) {
+            return;
+        }
         if (this.fileName.indexOf("APISample") >= 0) {
             return;
         }

tests/baselines/reference/conditionalTypeDoesntSpinForever.types

@@ -449,22 +449,22 @@ export enum PubSubRecordIsStoredInRedisAsA {
 >{} : {}
 
     buildNameFieldConstructor(soFar),
->buildNameFieldConstructor(soFar) : { name?: undefined; } | { name: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { name: TYPE; }>; }
+>buildNameFieldConstructor(soFar) : {} | { name: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { name: TYPE; }>; }
 >buildNameFieldConstructor : <SO_FAR>(soFar: SO_FAR) => { name?: undefined; } | { name: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { name: TYPE; }>; }
 >soFar : SO_FAR
 
     buildIdentifierFieldConstructor(soFar),
->buildIdentifierFieldConstructor(soFar) : { identifier?: undefined; } | { identifier: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { identifier: TYPE; }>; }
+>buildIdentifierFieldConstructor(soFar) : {} | { identifier: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { identifier: TYPE; }>; }
 >buildIdentifierFieldConstructor : <SO_FAR>(soFar: SO_FAR) => { identifier?: undefined; } | { identifier: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { identifier: TYPE; }>; }
 >soFar : SO_FAR
 
     buildRecordFieldConstructor(soFar),
->buildRecordFieldConstructor(soFar) : { record?: undefined; } | { record: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { record: TYPE; }>; }
+>buildRecordFieldConstructor(soFar) : {} | { record: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { record: TYPE; }>; }
 >buildRecordFieldConstructor : <SO_FAR>(soFar: SO_FAR) => { record?: undefined; } | { record: <TYPE>(instance?: TYPE) => BuildPubSubRecordType<SO_FAR & { record: TYPE; }>; }
 >soFar : SO_FAR
 
     buildStoredAsConstructor(soFar),
->buildStoredAsConstructor(soFar) : { storedAsJsonEncodedRedisString?: undefined; storedAsRedisHash?: undefined; } | { storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & { storedAs: PubSubRecordIsStoredInRedisAsA.jsonEncodedRedisString; }>; storedAsRedisHash: () => BuildPubSubRecordType<SO_FAR & { storedAs: PubSubRecordIsStoredInRedisAsA.redisHash; }>; }
+>buildStoredAsConstructor(soFar) : {} | { storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & { storedAs: PubSubRecordIsStoredInRedisAsA.jsonEncodedRedisString; }>; storedAsRedisHash: () => BuildPubSubRecordType<SO_FAR & { storedAs: PubSubRecordIsStoredInRedisAsA.redisHash; }>; }
 >buildStoredAsConstructor : <SO_FAR>(soFar: SO_FAR) => { storedAsJsonEncodedRedisString?: undefined; storedAsRedisHash?: undefined; } | { storedAsJsonEncodedRedisString: () => BuildPubSubRecordType<SO_FAR & { storedAs: PubSubRecordIsStoredInRedisAsA.jsonEncodedRedisString; }>; storedAsRedisHash: () => BuildPubSubRecordType<SO_FAR & { storedAs: PubSubRecordIsStoredInRedisAsA.redisHash; }>; }
 >soFar : SO_FAR
 
@@ -474,7 +474,7 @@ export enum PubSubRecordIsStoredInRedisAsA {
 >soFar : SO_FAR
 
     buildType(soFar)
->buildType(soFar) : { type?: undefined; fields?: undefined; hasField?: undefined; } | { type: SO_FAR; fields: () => Set<keyof SO_FAR>; hasField: (fieldName: string | number | symbol) => boolean; }
+>buildType(soFar) : {} | { type: SO_FAR; fields: () => Set<keyof SO_FAR>; hasField: (fieldName: string | number | symbol) => boolean; }
 >buildType : <SO_FAR>(soFar: SO_FAR) => { type?: undefined; fields?: undefined; hasField?: undefined; } | { type: SO_FAR; fields: () => Set<keyof SO_FAR>; hasField: (fieldName: string | number | symbol) => boolean; }
 >soFar : SO_FAR
 

tests/baselines/reference/objectLiteralNormalization.errors.txt

@@ -4,9 +4,9 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(9,1): error TS2322: Type '{ c: true; }' is not assignable to type '{ a: number; b?: undefined; c?: undefined; } | { a: number; b: string; c?: undefined; } | { a: number; b: string; c: boolean; }'.
   Type '{ c: true; }' is missing the following properties from type '{ a: number; b: string; c: boolean; }': a, b
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(17,1): error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
-  Type '{ a: string; b: number; }' is not assignable to type '{ a?: undefined; b?: undefined; }'.
+  Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; }'.
     Types of property 'a' are incompatible.
-      Type 'string' is not assignable to type 'undefined'.
+      Type 'string' is not assignable to type 'number'.
 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts(18,1): error TS2322: Type '{ a: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
   Property 'b' is missing in type '{ a: number; }' but required in type '{ a: number; b: number; }'.
 
@@ -21,7 +21,7 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
     a1 = { a: 0, b: 0 };  // Error
                  ~
 !!! error TS2322: Type 'number' is not assignable to type 'string | undefined'.
-!!! related TS6500 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts:2:47: The expected type comes from property 'b' which is declared here on type '{ a: number; b?: undefined; c?: undefined; } | { a: number; b: string; c?: undefined; } | { a: number; b: string; c: boolean; }'
+!!! related TS6500 tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts:2:29: The expected type comes from property 'b' which is declared here on type '{ a: number; b?: undefined; c?: undefined; } | { a: number; b: string; c?: undefined; } | { a: number; b: string; c: boolean; }'
     a1 = { b: "y" };  // Error
     ~~
 !!! error TS2322: Type '{ b: string; }' is not assignable to type '{ a: number; b?: undefined; c?: undefined; } | { a: number; b: string; c?: undefined; } | { a: number; b: string; c: boolean; }'.
@@ -40,9 +40,9 @@ tests/cases/conformance/expressions/objectLiterals/objectLiteralNormalization.ts
     a2 = { a: "def", b: 20 };  // Error
     ~~
 !!! error TS2322: Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.
-!!! error TS2322:   Type '{ a: string; b: number; }' is not assignable to type '{ a?: undefined; b?: undefined; }'.
+!!! error TS2322:   Type '{ a: string; b: number; }' is not assignable to type '{ a: number; b: number; }'.
 !!! error TS2322:     Types of property 'a' are incompatible.
-!!! error TS2322:       Type 'string' is not assignable to type 'undefined'.
+!!! error TS2322:       Type 'string' is not assignable to type 'number'.
     a2 = { a: 1 };  // Error
     ~~
 !!! error TS2322: Type '{ a: number; }' is not assignable to type '{ a: number; b: number; } | { a: string; b?: undefined; } | { a?: undefined; b?: undefined; }'.

tests/baselines/reference/objectLiteralNormalization.symbols

@@ -15,14 +15,14 @@ a1.a;  // number
 >a : Symbol(a, Decl(objectLiteralNormalization.ts, 1, 11), Decl(objectLiteralNormalization.ts, 1, 21), Decl(objectLiteralNormalization.ts, 1, 39))
 
 a1.b;  // string | undefined
->a1.b : Symbol(b, Decl(objectLiteralNormalization.ts, 1, 45), Decl(objectLiteralNormalization.ts, 1, 27), Decl(objectLiteralNormalization.ts, 1, 45))
+>a1.b : Symbol(b, Decl(objectLiteralNormalization.ts, 1, 27), Decl(objectLiteralNormalization.ts, 1, 45))
 >a1 : Symbol(a1, Decl(objectLiteralNormalization.ts, 1, 3))
->b : Symbol(b, Decl(objectLiteralNormalization.ts, 1, 45), Decl(objectLiteralNormalization.ts, 1, 27), Decl(objectLiteralNormalization.ts, 1, 45))
+>b : Symbol(b, Decl(objectLiteralNormalization.ts, 1, 27), Decl(objectLiteralNormalization.ts, 1, 45))
 
 a1.c;  // boolean | undefined
->a1.c : Symbol(c, Decl(objectLiteralNormalization.ts, 1, 53), Decl(objectLiteralNormalization.ts, 1, 53))
+>a1.c : Symbol(c, Decl(objectLiteralNormalization.ts, 1, 53))
 >a1 : Symbol(a1, Decl(objectLiteralNormalization.ts, 1, 3))
->c : Symbol(c, Decl(objectLiteralNormalization.ts, 1, 53), Decl(objectLiteralNormalization.ts, 1, 53))
+>c : Symbol(c, Decl(objectLiteralNormalization.ts, 1, 53))
 
 a1 = { a: 1 };
 >a1 : Symbol(a1, Decl(objectLiteralNormalization.ts, 1, 3))
@@ -48,14 +48,14 @@ let a2 = [{ a: 1, b: 2 }, { a: "abc" }, {}][0];
 >a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 27))
 
 a2.a;  // string | number | undefined
->a2.a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 11), Decl(objectLiteralNormalization.ts, 10, 27), Decl(objectLiteralNormalization.ts, 10, 27))
+>a2.a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 11), Decl(objectLiteralNormalization.ts, 10, 27))
 >a2 : Symbol(a2, Decl(objectLiteralNormalization.ts, 10, 3))
->a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 11), Decl(objectLiteralNormalization.ts, 10, 27), Decl(objectLiteralNormalization.ts, 10, 27))
+>a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 11), Decl(objectLiteralNormalization.ts, 10, 27))
 
 a2.b;  // number | undefined
->a2.b : Symbol(b, Decl(objectLiteralNormalization.ts, 10, 17), Decl(objectLiteralNormalization.ts, 1, 45))
+>a2.b : Symbol(b, Decl(objectLiteralNormalization.ts, 10, 17))
 >a2 : Symbol(a2, Decl(objectLiteralNormalization.ts, 10, 3))
->b : Symbol(b, Decl(objectLiteralNormalization.ts, 10, 17), Decl(objectLiteralNormalization.ts, 1, 45))
+>b : Symbol(b, Decl(objectLiteralNormalization.ts, 10, 17))
 
 a2 = { a: 10, b: 20 };
 >a2 : Symbol(a2, Decl(objectLiteralNormalization.ts, 10, 3))
@@ -144,32 +144,32 @@ d1.pos;
 >pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
 
 d1.pos.x;
->d1.pos.x : Symbol(x, Decl(objectLiteralNormalization.ts, 33, 29), Decl(objectLiteralNormalization.ts, 33, 29))
+>d1.pos.x : Symbol(x, Decl(objectLiteralNormalization.ts, 33, 29))
 >d1.pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
 >d1 : Symbol(d1, Decl(objectLiteralNormalization.ts, 33, 3))
 >pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
->x : Symbol(x, Decl(objectLiteralNormalization.ts, 33, 29), Decl(objectLiteralNormalization.ts, 33, 29))
+>x : Symbol(x, Decl(objectLiteralNormalization.ts, 33, 29))
 
 d1.pos.y;
->d1.pos.y : Symbol(y, Decl(objectLiteralNormalization.ts, 33, 35), Decl(objectLiteralNormalization.ts, 33, 35))
+>d1.pos.y : Symbol(y, Decl(objectLiteralNormalization.ts, 33, 35))
 >d1.pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
 >d1 : Symbol(d1, Decl(objectLiteralNormalization.ts, 33, 3))
 >pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
->y : Symbol(y, Decl(objectLiteralNormalization.ts, 33, 35), Decl(objectLiteralNormalization.ts, 33, 35))
+>y : Symbol(y, Decl(objectLiteralNormalization.ts, 33, 35))
 
 d1.pos.a;
->d1.pos.a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 27), Decl(objectLiteralNormalization.ts, 33, 73))
+>d1.pos.a : Symbol(a, Decl(objectLiteralNormalization.ts, 33, 73))
 >d1.pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
 >d1 : Symbol(d1, Decl(objectLiteralNormalization.ts, 33, 3))
 >pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
->a : Symbol(a, Decl(objectLiteralNormalization.ts, 10, 27), Decl(objectLiteralNormalization.ts, 33, 73))
+>a : Symbol(a, Decl(objectLiteralNormalization.ts, 33, 73))
 
 d1.pos.b;
->d1.pos.b : Symbol(b, Decl(objectLiteralNormalization.ts, 1, 45), Decl(objectLiteralNormalization.ts, 33, 86))
+>d1.pos.b : Symbol(b, Decl(objectLiteralNormalization.ts, 33, 86))
 >d1.pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
 >d1 : Symbol(d1, Decl(objectLiteralNormalization.ts, 33, 3))
 >pos : Symbol(pos, Decl(objectLiteralNormalization.ts, 33, 22), Decl(objectLiteralNormalization.ts, 33, 58))
->b : Symbol(b, Decl(objectLiteralNormalization.ts, 1, 45), Decl(objectLiteralNormalization.ts, 33, 86))
+>b : Symbol(b, Decl(objectLiteralNormalization.ts, 33, 86))
 
 declare function f<T>(...items: T[]): T;
 >f : Symbol(f, Decl(objectLiteralNormalization.ts, 39, 9))

tests/baselines/reference/typeFromPropertyAssignment29.symbols

@@ -66,11 +66,11 @@ ExpandoExpr.m = function(n: number) {
 }
 var n = (ExpandoExpr.prop.x || 0) + ExpandoExpr.m(12) + ExpandoExpr(101).length
 >n : Symbol(n, Decl(typeFromPropertyAssignment29.ts, 7, 3), Decl(typeFromPropertyAssignment29.ts, 17, 3), Decl(typeFromPropertyAssignment29.ts, 45, 3), Decl(typeFromPropertyAssignment29.ts, 63, 3), Decl(typeFromPropertyAssignment29.ts, 73, 3) ... and 1 more)
->ExpandoExpr.prop.x : Symbol(x, Decl(typeFromPropertyAssignment29.ts, 12, 20))
+>ExpandoExpr.prop.x : Symbol(x)
 >ExpandoExpr.prop : Symbol(ExpandoExpr.prop, Decl(typeFromPropertyAssignment29.ts, 11, 1), Decl(typeFromPropertyAssignment29.ts, 12, 27))
 >ExpandoExpr : Symbol(ExpandoExpr, Decl(typeFromPropertyAssignment29.ts, 9, 5), Decl(typeFromPropertyAssignment29.ts, 11, 1))
 >prop : Symbol(ExpandoExpr.prop, Decl(typeFromPropertyAssignment29.ts, 11, 1), Decl(typeFromPropertyAssignment29.ts, 12, 27))
->x : Symbol(x, Decl(typeFromPropertyAssignment29.ts, 12, 20))
+>x : Symbol(x)
 >ExpandoExpr.m : Symbol(ExpandoExpr.m, Decl(typeFromPropertyAssignment29.ts, 13, 28))
 >ExpandoExpr : Symbol(ExpandoExpr, Decl(typeFromPropertyAssignment29.ts, 9, 5), Decl(typeFromPropertyAssignment29.ts, 11, 1))
 >m : Symbol(ExpandoExpr.m, Decl(typeFromPropertyAssignment29.ts, 13, 28))

tests/baselines/reference/typeFromPropertyAssignment29.types

@@ -96,9 +96,9 @@ var n = (ExpandoExpr.prop.x || 0) + ExpandoExpr.m(12) + ExpandoExpr(101).length
 >(ExpandoExpr.prop.x || 0) : 0
 >ExpandoExpr.prop.x || 0 : 0
 >ExpandoExpr.prop.x : undefined
->ExpandoExpr.prop : { y: string; x?: undefined; }
+>ExpandoExpr.prop : { y: string; }
 >ExpandoExpr : { (n: number): string; prop: { x: number; y?: undefined; } | { y: string; x?: undefined; }; m(n: number): number; }
->prop : { y: string; x?: undefined; }
+>prop : { y: string; }
 >x : undefined
 >0 : 0
 >ExpandoExpr.m(12) : number