Type guard by deep property

src/compiler/sys.ts

@@ -1283,8 +1283,8 @@ namespace ts {
 
  const platform: string = _os.platform();
  const useCaseSensitiveFileNames = isFileSystemCaseSensitive();
- const realpathSync = _fs.realpathSync.native ?? _fs.realpathSync;
-
+ // Use `any` to avoid type narrow.
+ const realpathSync = (_fs as any).realpathSync.native ?? _fs.realpathSync;
  const fsSupportsRecursiveFsWatch = isNode4OrLater && (process.platform === "win32" || process.platform === "darwin");
  const getCurrentDirectory = memoize(() => process.cwd());
  const { watchFile, watchDirectory } = createSystemWatchFunctions({

src/server/session.ts

@@ -1516,7 +1516,8 @@ namespace ts.server {
  // filter handles case when 'projects' is undefined
  projects = filter(projects, p => p.languageServiceEnabled && !p.isOrphan());
  if (!ignoreNoProjectError && (!projects || !projects.length) && !symLinkedProjects) {
- this.projectService.logErrorForScriptInfoNotFound(args.file ?? args.projectFileName);
+ // use `any` to avoid type narrow
+ this.projectService.logErrorForScriptInfoNotFound((args as any).file ?? args.projectFileName);
  return Errors.ThrowNoProject();
  }
  return symLinkedProjects ? { projects: projects!, symLinkedProjects } : projects!; // TODO: GH#18217

tests/baselines/reference/controlFlowOptionalChain.errors.txt

@@ -57,11 +57,10 @@ tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(463,9): error TS
 tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(498,13): error TS2532: Object is possibly 'undefined'.
 tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(501,13): error TS2532: Object is possibly 'undefined'.
 tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(515,13): error TS2532: Object is possibly 'undefined'.
-tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(518,13): error TS2532: Object is possibly 'undefined'.
 tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(567,21): error TS2532: Object is possibly 'undefined'.
 
 
-==== tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts (61 errors) ====
+==== tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts (60 errors) ====
  // assignments in shortcutting chain
  declare const o: undefined | {
  [key: string]: any;
@@ -697,9 +696,7 @@ tests/cases/conformance/controlFlow/controlFlowOptionalChain.ts(567,21): error T
 !!! error TS2532: Object is possibly 'undefined'.
  break;
  default:
- o.foo; // Error
- ~
-!!! error TS2532: Object is possibly 'undefined'.
+ o.foo;
  break;
  }
  }

tests/baselines/reference/controlFlowOptionalChain.js

@@ -516,7 +516,7 @@ function f41(o: Thing | undefined) {
  o.foo; // Error
  break;
  default:
- o.foo; // Error
+ o.foo;
  break;
  }
 }
@@ -1049,7 +1049,7 @@ function f41(o) {
  o.foo; // Error
  break;
  default:
- o.foo; // Error
+ o.foo;
  break;
  }
 }

tests/baselines/reference/controlFlowOptionalChain.symbols

@@ -1438,9 +1438,7 @@ function f23(o: Thing | undefined) {
 >foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 
  o.foo; // Error
->o.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 439, 13))
->foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
  }
  else {
  o.foo;
@@ -1460,19 +1458,15 @@ function f23(o: Thing | undefined) {
  }
  else {
  o.foo; // Error
->o.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 439, 13))
->foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
  }
  if (typeof o?.foo == "undefined") {
 >o?.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 439, 13))
 >foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 
  o.foo; // Error
->o.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 439, 13))
->foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
  }
  else {
  o.foo;
@@ -1492,9 +1486,7 @@ function f23(o: Thing | undefined) {
  }
  else {
  o.foo; // Error
->o.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 439, 13))
->foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
  }
 }
 
@@ -1636,13 +1628,11 @@ function f41(o: Thing | undefined) {
  break;
  case "undefined":
  o.foo; // Error
->o.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 505, 13))
->foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 
  break;
  default:
- o.foo; // Error
+ o.foo;
 >o.foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))
 >o : Symbol(o, Decl(controlFlowOptionalChain.ts, 505, 13))
 >foo : Symbol(foo, Decl(controlFlowOptionalChain.ts, 161, 14))

tests/baselines/reference/controlFlowOptionalChain.types

@@ -1618,9 +1618,9 @@ function f23(o: Thing | undefined) {
 >"undefined" : "undefined"
 
  o.foo; // Error
->o.foo : never
->o : Thing | undefined
->foo : never
+>o.foo : any
+>o : undefined
+>foo : any
  }
  else {
  o.foo;
@@ -1643,9 +1643,9 @@ function f23(o: Thing | undefined) {
  }
  else {
  o.foo; // Error
->o.foo : never
->o : Thing | undefined
->foo : never
+>o.foo : any
+>o : undefined
+>foo : any
  }
  if (typeof o?.foo == "undefined") {
 >typeof o?.foo == "undefined" : boolean
@@ -1656,9 +1656,9 @@ function f23(o: Thing | undefined) {
 >"undefined" : "undefined"
 
  o.foo; // Error
->o.foo : never
->o : Thing | undefined
->foo : never
+>o.foo : any
+>o : undefined
+>foo : any
  }
  else {
  o.foo;
@@ -1681,9 +1681,9 @@ function f23(o: Thing | undefined) {
  }
  else {
  o.foo; // Error
->o.foo : never
->o : Thing | undefined
->foo : never
+>o.foo : any
+>o : undefined
+>foo : any
  }
 }
 
@@ -1852,15 +1852,15 @@ function f41(o: Thing | undefined) {
 >"undefined" : "undefined"
 
  o.foo; // Error
->o.foo : never
->o : Thing | undefined
->foo : never
+>o.foo : any
+>o : undefined
+>foo : any
 
  break;
  default:
- o.foo; // Error
+ o.foo;
 >o.foo : never
->o : Thing | undefined
+>o : Thing
 >foo : never
 
  break;

tests/baselines/reference/destructuringControlFlow.types

@@ -63,34 +63,34 @@ function f2(obj: [number, string] | null[]) {
 >obj[0] : number | null
 >obj : [number, string] | null[]
 >0 : 0
->obj[1] : string | null
->obj : [number, string] | null[]
+>obj[1] : string
+>obj : [number, string]
 >1 : 1
 
  let c0 = obj[0]; // number
 >c0 : number
 >obj[0] : number
->obj : [number, string] | null[]
+>obj : [number, string]
 >0 : 0
 
  let c1 = obj[1]; // string
 >c1 : string
 >obj[1] : string
->obj : [number, string] | null[]
+>obj : [number, string]
 >1 : 1
 
  let [d0, d1] = obj;
 >d0 : number
 >d1 : string
->obj : [number, string] | null[]
+>obj : [number, string]
 
  ([c0, c1] = obj);
->([c0, c1] = obj) : [number, string] | null[]
->[c0, c1] = obj : [number, string] | null[]
+>([c0, c1] = obj) : [number, string]
+>[c0, c1] = obj : [number, string]
 >[c0, c1] : [number, string]
 >c0 : number
 >c1 : string
->obj : [number, string] | null[]
+>obj : [number, string]
  }
 }
 

tests/baselines/reference/discriminatedUnionTypes2.errors.txt

@@ -2,9 +2,10 @@ tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(27,30): error TS
  Object literal may only specify known properties, and 'c' does not exist in type '{ a: null; b: string; }'.
 tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(32,11): error TS2339: Property 'b' does not exist on type '{ a: 0; b: string; } | { a: T; c: number; }'.
  Property 'b' does not exist on type '{ a: T; c: number; }'.
+tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(132,11): error TS2339: Property 'value' does not exist on type 'never'.
 
 
-==== tests/cases/conformance/types/union/discriminatedUnionTypes2.ts (2 errors) ====
+==== tests/cases/conformance/types/union/discriminatedUnionTypes2.ts (3 errors) ====
  function f10(x : { kind: false, a: string } | { kind: true, b: string } | { kind: string, c: string }) {
  if (x.kind === false) {
  x.a;
@@ -142,7 +143,9 @@ tests/cases/conformance/types/union/discriminatedUnionTypes2.ts(32,11): error TS
  x.value; // number
  }
  else {
- x.value; // number
+ x.value; // Error, x is never
+ ~~~~~
+!!! error TS2339: Property 'value' does not exist on type 'never'.
  }
  }
 

tests/baselines/reference/discriminatedUnionTypes2.js

@@ -130,7 +130,7 @@ function foo1(x: RuntimeValue & { type: 'number' }) {
  x.value; // number
  }
  else {
- x.value; // number
+ x.value; // Error, x is never
  }
 }
 
@@ -226,7 +226,7 @@ function foo1(x) {
  x.value; // number
  }
  else {
- x.value; // number
+ x.value; // Error, x is never
  }
 }
 function foo2(x) {

tests/baselines/reference/discriminatedUnionTypes2.symbols

@@ -366,10 +366,8 @@ function foo1(x: RuntimeValue & { type: 'number' }) {
 >value : Symbol(value, Decl(discriminatedUnionTypes2.ts, 122, 23))
  }
  else {
- x.value; // number
->x.value : Symbol(value, Decl(discriminatedUnionTypes2.ts, 122, 23))
+ x.value; // Error, x is never
 >x : Symbol(x, Decl(discriminatedUnionTypes2.ts, 126, 14))
->value : Symbol(value, Decl(discriminatedUnionTypes2.ts, 122, 23))
  }
 }
 

tests/baselines/reference/discriminatedUnionTypes2.types

@@ -379,10 +379,10 @@ function foo1(x: RuntimeValue & { type: 'number' }) {
 >value : number
  }
  else {
- x.value; // number
->x.value : number
->x : { type: "number"; value: number; } & { type: "number"; }
->value : number
+ x.value; // Error, x is never
+>x.value : any
+>x : never
+>value : any
  }
 }
 

tests/baselines/reference/discriminatedUnionTypes3.errors.txt

@@ -0,0 +1,91 @@
+tests/cases/conformance/types/union/discriminatedUnionTypes3.ts(59,11): error TS2339: Property 's' does not exist on type 'T'.
+tests/cases/conformance/types/union/discriminatedUnionTypes3.ts(78,10): error TS2339: Property 'property' does not exist on type 'SomeReturnType'.
+ Property 'property' does not exist on type 'Err'.
+
+
+==== tests/cases/conformance/types/union/discriminatedUnionTypes3.ts (2 errors) ====
+ type A = { type2: "a", a: number }
+ type B = { type2: "b", b: number }
+ type C = { type2: "c", b: number | string }
+
+ type X = { type1: A, x: string }
+ type Y = { type1: B, y: string }
+ type Z = { type1: C, z: string }
+ type W = { type1: undefined }
+
+ function f32(x: X | Y) {
+ switch (x.type1.type2) {
+ case "a":
+ x.x // typeof x is X
+ break;
+ case "b":
+ x.y // typeof x is Y
+ break;
+ }
+ }
+
+ function f33(x: A | B) {
+ switch (x.type2) {
+ case "a":
+ x // typeof x is X
+ break;
+ case "b":
+ x // typeof x is Y
+ break;
+ }
+ }
+
+ function f34(x: X | Y) {
+ if (x.type1.type2 === "a") {
+ x.x // typeof x is X
+ } else if (x.type1.type2 === "b") {
+ x.y // typeof x is Y
+ }
+ }
+
+ function f35(x: X | W) {
+ if (x.type1?.type2 === "a") {
+ x.x
+ }
+ }
+
+ function f36(x: X | W) {
+ x.type1?.type2 ?? x;
+ }
+
+ type S = { sub: { type0: X }, s: string }
+ type T = { sub: { type0: Y }, t: string }
+
+ function f37(s: S | T) {
+ if (s.sub.type0.type1.type2 === "a") {
+ s.s // typeof s is S
+ s.sub.type0.x // type of s.sub.type is X
+ s.sub.type0.type1.a // type of s.sub.type.type is A
+ } else {
+ s.s // type error!
+ ~
+!!! error TS2339: Property 's' does not exist on type 'T'.
+ }
+ }
+
+ // Repro from #44435
+
+ type Correct = {
+ code: string
+ property: true
+ err: undefined
+ }
+ type Err = {
+ err: `${string} is wrong!`
+ }
+ type SomeReturnType = Correct | Err;
+
+ const example: SomeReturnType = {} as SomeReturnType;
+
+ if (example.err === undefined) {
+ example.property; // true
+ ~~~~~~~~
+!!! error TS2339: Property 'property' does not exist on type 'SomeReturnType'.
+!!! error TS2339: Property 'property' does not exist on type 'Err'.
+ }
+