Accepted baselines.

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

@@ -2136,6 +2136,7 @@ declare namespace ts {
         OmitParameterModifiers = 8192,
         UseAliasDefinedOutsideCurrentScope = 16384,
         UseSingleQuotesForStringLiteralType = 268435456,
+        PreserveVacuousIntersections = 536870912,
         AllowThisInObjectLiteral = 32768,
         AllowQualifedNameInPlaceOfIdentifier = 65536,
         AllowAnonymousIdentifier = 131072,
@@ -2164,6 +2165,7 @@ declare namespace ts {
         OmitParameterModifiers = 8192,
         UseAliasDefinedOutsideCurrentScope = 16384,
         UseSingleQuotesForStringLiteralType = 268435456,
+        PreserveVacuousIntersections = 536870912,
         AllowUniqueESSymbolType = 1048576,
         AddUndefined = 131072,
         WriteArrowStyleSignature = 262144,
@@ -2172,7 +2174,7 @@ declare namespace ts {
         InFirstTypeArgument = 4194304,
         InTypeAlias = 8388608,
         /** @deprecated */ WriteOwnNameForAnyLike = 0,
-        NodeBuilderFlagsMask = 277904747
+        NodeBuilderFlagsMask = 814775659
     }
     export enum SymbolFormatFlags {
         None = 0,

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

@@ -2136,6 +2136,7 @@ declare namespace ts {
         OmitParameterModifiers = 8192,
         UseAliasDefinedOutsideCurrentScope = 16384,
         UseSingleQuotesForStringLiteralType = 268435456,
+        PreserveVacuousIntersections = 536870912,
         AllowThisInObjectLiteral = 32768,
         AllowQualifedNameInPlaceOfIdentifier = 65536,
         AllowAnonymousIdentifier = 131072,
@@ -2164,6 +2165,7 @@ declare namespace ts {
         OmitParameterModifiers = 8192,
         UseAliasDefinedOutsideCurrentScope = 16384,
         UseSingleQuotesForStringLiteralType = 268435456,
+        PreserveVacuousIntersections = 536870912,
         AllowUniqueESSymbolType = 1048576,
         AddUndefined = 131072,
         WriteArrowStyleSignature = 262144,
@@ -2172,7 +2174,7 @@ declare namespace ts {
         InFirstTypeArgument = 4194304,
         InTypeAlias = 8388608,
         /** @deprecated */ WriteOwnNameForAnyLike = 0,
-        NodeBuilderFlagsMask = 277904747
+        NodeBuilderFlagsMask = 814775659
     }
     export enum SymbolFormatFlags {
         None = 0,

tests/baselines/reference/intersectionReduction.errors.txt

@@ -1,9 +1,12 @@
 tests/cases/conformance/types/intersection/intersectionReduction.ts(38,4): error TS2339: Property 'kind' does not exist on type 'never'.
-tests/cases/conformance/types/intersection/intersectionReduction.ts(80,1): error TS2322: Type 'any' is not assignable to type 'never'.
+  The type 'never' was reduced from the intersection 'A & B'. Each type of that intersection has properties that conflict, so values of that type can never exist.
+tests/cases/conformance/types/intersection/intersectionReduction.ts(39,1): error TS2322: Type '42' is not assignable to type 'never'.
+  The type 'never' was reduced from the intersection 'A & B'. Each type of that intersection has properties that conflict, so values of that type can never exist.
 tests/cases/conformance/types/intersection/intersectionReduction.ts(81,1): error TS2322: Type 'any' is not assignable to type 'never'.
+tests/cases/conformance/types/intersection/intersectionReduction.ts(82,1): error TS2322: Type 'any' is not assignable to type 'never'.
 
 
-==== tests/cases/conformance/types/intersection/intersectionReduction.ts (3 errors) ====
+==== tests/cases/conformance/types/intersection/intersectionReduction.ts (4 errors) ====
     declare const sym1: unique symbol;
     declare const sym2: unique symbol;
     
@@ -44,6 +47,11 @@ tests/cases/conformance/types/intersection/intersectionReduction.ts(81,1): error
     ab.kind;  // Error
        ~~~~
 !!! error TS2339: Property 'kind' does not exist on type 'never'.
+!!! error TS2339:   The type 'never' was reduced from the intersection 'A & B'. Each type of that intersection has properties that conflict, so values of that type can never exist.
+    ab = 42;
+    ~~
+!!! error TS2322: Type '42' is not assignable to type 'never'.
+!!! error TS2322:   The type 'never' was reduced from the intersection 'A & B'. Each type of that intersection has properties that conflict, so values of that type can never exist.
     
     declare let x: A | (B & C);  // A
     let a: A = x;

tests/baselines/reference/intersectionReduction.js

@@ -37,6 +37,7 @@ type C = { kind: 'c', foo: number };
 
 declare let ab: A & B;
 ab.kind;  // Error
+ab = 42;
 
 declare let x: A | (B & C);  // A
 let a: A = x;
@@ -111,6 +112,7 @@ const f4 = (t: number | (Container<"b"> & { dataB: boolean } & Container<"a">)):
 
 //// [intersectionReduction.js]
 ab.kind; // Error
+ab = 42;
 var a = x;
 var r1 = f10(a1); // unknown
 var r2 = f10(a2); // string

tests/baselines/reference/intersectionReduction.symbols

@@ -116,260 +116,263 @@ declare let ab: A & B;
 ab.kind;  // Error
 >ab : Symbol(ab, Decl(intersectionReduction.ts, 36, 11))
 
+ab = 42;
+>ab : Symbol(ab, Decl(intersectionReduction.ts, 36, 11))
+
 declare let x: A | (B & C);  // A
->x : Symbol(x, Decl(intersectionReduction.ts, 39, 11))
+>x : Symbol(x, Decl(intersectionReduction.ts, 40, 11))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 >C : Symbol(C, Decl(intersectionReduction.ts, 33, 36))
 
 let a: A = x;
->a : Symbol(a, Decl(intersectionReduction.ts, 40, 3))
+>a : Symbol(a, Decl(intersectionReduction.ts, 41, 3))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
->x : Symbol(x, Decl(intersectionReduction.ts, 39, 11))
+>x : Symbol(x, Decl(intersectionReduction.ts, 40, 11))
 
 type AB = A & B;  // never
->AB : Symbol(AB, Decl(intersectionReduction.ts, 40, 13))
+>AB : Symbol(AB, Decl(intersectionReduction.ts, 41, 13))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 
 type BC = B & C;  // never
->BC : Symbol(BC, Decl(intersectionReduction.ts, 42, 16))
+>BC : Symbol(BC, Decl(intersectionReduction.ts, 43, 16))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 >C : Symbol(C, Decl(intersectionReduction.ts, 33, 36))
 
 type U1 = Partial<A & B>;  // never
->U1 : Symbol(U1, Decl(intersectionReduction.ts, 43, 16))
+>U1 : Symbol(U1, Decl(intersectionReduction.ts, 44, 16))
 >Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 
 type U2 = Readonly<A & B>;  // never
->U2 : Symbol(U2, Decl(intersectionReduction.ts, 45, 25))
+>U2 : Symbol(U2, Decl(intersectionReduction.ts, 46, 25))
 >Readonly : Symbol(Readonly, Decl(lib.es5.d.ts, --, --))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 
 type U3 = (A & B)['kind'];  // never
->U3 : Symbol(U3, Decl(intersectionReduction.ts, 46, 26))
+>U3 : Symbol(U3, Decl(intersectionReduction.ts, 47, 26))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 
 type U4 = A & B | B & C;  // never
->U4 : Symbol(U4, Decl(intersectionReduction.ts, 47, 26))
+>U4 : Symbol(U4, Decl(intersectionReduction.ts, 48, 26))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 >C : Symbol(C, Decl(intersectionReduction.ts, 33, 36))
 
 type U5 = A | B & C;  // A
->U5 : Symbol(U5, Decl(intersectionReduction.ts, 48, 24))
+>U5 : Symbol(U5, Decl(intersectionReduction.ts, 49, 24))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 >C : Symbol(C, Decl(intersectionReduction.ts, 33, 36))
 
 type K1 = keyof (A & B);  // string | number | symbol
->K1 : Symbol(K1, Decl(intersectionReduction.ts, 49, 20))
+>K1 : Symbol(K1, Decl(intersectionReduction.ts, 50, 20))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 
 type K2 = keyof A | keyof B;  // 'kind' | 'foo'
->K2 : Symbol(K2, Decl(intersectionReduction.ts, 51, 24))
+>K2 : Symbol(K2, Decl(intersectionReduction.ts, 52, 24))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
 >B : Symbol(B, Decl(intersectionReduction.ts, 32, 36))
 
 type Merge1<T, U> = { [P in keyof (T & U)]: P extends keyof T ? T[P] : U[P & keyof U] }
->Merge1 : Symbol(Merge1, Decl(intersectionReduction.ts, 52, 28))
->T : Symbol(T, Decl(intersectionReduction.ts, 54, 12))
->U : Symbol(U, Decl(intersectionReduction.ts, 54, 14))
->P : Symbol(P, Decl(intersectionReduction.ts, 54, 23))
->T : Symbol(T, Decl(intersectionReduction.ts, 54, 12))
->U : Symbol(U, Decl(intersectionReduction.ts, 54, 14))
->P : Symbol(P, Decl(intersectionReduction.ts, 54, 23))
->T : Symbol(T, Decl(intersectionReduction.ts, 54, 12))
->T : Symbol(T, Decl(intersectionReduction.ts, 54, 12))
->P : Symbol(P, Decl(intersectionReduction.ts, 54, 23))
->U : Symbol(U, Decl(intersectionReduction.ts, 54, 14))
->P : Symbol(P, Decl(intersectionReduction.ts, 54, 23))
->U : Symbol(U, Decl(intersectionReduction.ts, 54, 14))
+>Merge1 : Symbol(Merge1, Decl(intersectionReduction.ts, 53, 28))
+>T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
+>U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
+>P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
+>T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
+>U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
+>P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
+>T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
+>T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
+>P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
+>U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
+>P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
+>U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
 
 type Merge2<T, U> = { [P in keyof T | keyof U]: P extends keyof T ? T[P] : U[P & keyof U] }
->Merge2 : Symbol(Merge2, Decl(intersectionReduction.ts, 54, 87))
->T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
->U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
->P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
->T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
->U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
->P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
->T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
->T : Symbol(T, Decl(intersectionReduction.ts, 55, 12))
->P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
->U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
->P : Symbol(P, Decl(intersectionReduction.ts, 55, 23))
->U : Symbol(U, Decl(intersectionReduction.ts, 55, 14))
+>Merge2 : Symbol(Merge2, Decl(intersectionReduction.ts, 55, 87))
+>T : Symbol(T, Decl(intersectionReduction.ts, 56, 12))
+>U : Symbol(U, Decl(intersectionReduction.ts, 56, 14))
+>P : Symbol(P, Decl(intersectionReduction.ts, 56, 23))
+>T : Symbol(T, Decl(intersectionReduction.ts, 56, 12))
+>U : Symbol(U, Decl(intersectionReduction.ts, 56, 14))
+>P : Symbol(P, Decl(intersectionReduction.ts, 56, 23))
+>T : Symbol(T, Decl(intersectionReduction.ts, 56, 12))
+>T : Symbol(T, Decl(intersectionReduction.ts, 56, 12))
+>P : Symbol(P, Decl(intersectionReduction.ts, 56, 23))
+>U : Symbol(U, Decl(intersectionReduction.ts, 56, 14))
+>P : Symbol(P, Decl(intersectionReduction.ts, 56, 23))
+>U : Symbol(U, Decl(intersectionReduction.ts, 56, 14))
 
 type M1 = { a: 1, b: 2 } & { a: 2, c: 3 };  // never
->M1 : Symbol(M1, Decl(intersectionReduction.ts, 55, 91))
->a : Symbol(a, Decl(intersectionReduction.ts, 57, 11))
->b : Symbol(b, Decl(intersectionReduction.ts, 57, 17))
->a : Symbol(a, Decl(intersectionReduction.ts, 57, 28))
->c : Symbol(c, Decl(intersectionReduction.ts, 57, 34))
+>M1 : Symbol(M1, Decl(intersectionReduction.ts, 56, 91))
+>a : Symbol(a, Decl(intersectionReduction.ts, 58, 11))
+>b : Symbol(b, Decl(intersectionReduction.ts, 58, 17))
+>a : Symbol(a, Decl(intersectionReduction.ts, 58, 28))
+>c : Symbol(c, Decl(intersectionReduction.ts, 58, 34))
 
 type M2 = Merge1<{ a: 1, b: 2 }, { a: 2, c: 3 }>;  // {}
->M2 : Symbol(M2, Decl(intersectionReduction.ts, 57, 42))
->Merge1 : Symbol(Merge1, Decl(intersectionReduction.ts, 52, 28))
->a : Symbol(a, Decl(intersectionReduction.ts, 58, 18))
->b : Symbol(b, Decl(intersectionReduction.ts, 58, 24))
->a : Symbol(a, Decl(intersectionReduction.ts, 58, 34))
->c : Symbol(c, Decl(intersectionReduction.ts, 58, 40))
-
-type M3 = Merge2<{ a: 1, b: 2 }, { a: 2, c: 3 }>;  // { a: 1, b: 2, c: 3 }
->M3 : Symbol(M3, Decl(intersectionReduction.ts, 58, 49))
->Merge2 : Symbol(Merge2, Decl(intersectionReduction.ts, 54, 87))
+>M2 : Symbol(M2, Decl(intersectionReduction.ts, 58, 42))
+>Merge1 : Symbol(Merge1, Decl(intersectionReduction.ts, 53, 28))
 >a : Symbol(a, Decl(intersectionReduction.ts, 59, 18))
 >b : Symbol(b, Decl(intersectionReduction.ts, 59, 24))
 >a : Symbol(a, Decl(intersectionReduction.ts, 59, 34))
 >c : Symbol(c, Decl(intersectionReduction.ts, 59, 40))
 
-type D = { kind: 'd', foo: unknown };
->D : Symbol(D, Decl(intersectionReduction.ts, 59, 49))
->kind : Symbol(kind, Decl(intersectionReduction.ts, 61, 10))
->foo : Symbol(foo, Decl(intersectionReduction.ts, 61, 21))
+type M3 = Merge2<{ a: 1, b: 2 }, { a: 2, c: 3 }>;  // { a: 1, b: 2, c: 3 }
+>M3 : Symbol(M3, Decl(intersectionReduction.ts, 59, 49))
+>Merge2 : Symbol(Merge2, Decl(intersectionReduction.ts, 55, 87))
+>a : Symbol(a, Decl(intersectionReduction.ts, 60, 18))
+>b : Symbol(b, Decl(intersectionReduction.ts, 60, 24))
+>a : Symbol(a, Decl(intersectionReduction.ts, 60, 34))
+>c : Symbol(c, Decl(intersectionReduction.ts, 60, 40))
 
-type E = { kind: 'e', foo: unknown };
->E : Symbol(E, Decl(intersectionReduction.ts, 61, 37))
+type D = { kind: 'd', foo: unknown };
+>D : Symbol(D, Decl(intersectionReduction.ts, 60, 49))
 >kind : Symbol(kind, Decl(intersectionReduction.ts, 62, 10))
 >foo : Symbol(foo, Decl(intersectionReduction.ts, 62, 21))
 
+type E = { kind: 'e', foo: unknown };
+>E : Symbol(E, Decl(intersectionReduction.ts, 62, 37))
+>kind : Symbol(kind, Decl(intersectionReduction.ts, 63, 10))
+>foo : Symbol(foo, Decl(intersectionReduction.ts, 63, 21))
+
 declare function f10<T>(x: { foo: T }): T;
->f10 : Symbol(f10, Decl(intersectionReduction.ts, 62, 37))
->T : Symbol(T, Decl(intersectionReduction.ts, 64, 21))
->x : Symbol(x, Decl(intersectionReduction.ts, 64, 24))
->foo : Symbol(foo, Decl(intersectionReduction.ts, 64, 28))
->T : Symbol(T, Decl(intersectionReduction.ts, 64, 21))
->T : Symbol(T, Decl(intersectionReduction.ts, 64, 21))
+>f10 : Symbol(f10, Decl(intersectionReduction.ts, 63, 37))
+>T : Symbol(T, Decl(intersectionReduction.ts, 65, 21))
+>x : Symbol(x, Decl(intersectionReduction.ts, 65, 24))
+>foo : Symbol(foo, Decl(intersectionReduction.ts, 65, 28))
+>T : Symbol(T, Decl(intersectionReduction.ts, 65, 21))
+>T : Symbol(T, Decl(intersectionReduction.ts, 65, 21))
 
 declare let a1: A | D;
->a1 : Symbol(a1, Decl(intersectionReduction.ts, 66, 11))
+>a1 : Symbol(a1, Decl(intersectionReduction.ts, 67, 11))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
->D : Symbol(D, Decl(intersectionReduction.ts, 59, 49))
+>D : Symbol(D, Decl(intersectionReduction.ts, 60, 49))
 
 declare let a2: A | D & E;
->a2 : Symbol(a2, Decl(intersectionReduction.ts, 67, 11))
+>a2 : Symbol(a2, Decl(intersectionReduction.ts, 68, 11))
 >A : Symbol(A, Decl(intersectionReduction.ts, 30, 28))
->D : Symbol(D, Decl(intersectionReduction.ts, 59, 49))
->E : Symbol(E, Decl(intersectionReduction.ts, 61, 37))
+>D : Symbol(D, Decl(intersectionReduction.ts, 60, 49))
+>E : Symbol(E, Decl(intersectionReduction.ts, 62, 37))
 
 let r1 = f10(a1);  // unknown
->r1 : Symbol(r1, Decl(intersectionReduction.ts, 69, 3))
->f10 : Symbol(f10, Decl(intersectionReduction.ts, 62, 37))
->a1 : Symbol(a1, Decl(intersectionReduction.ts, 66, 11))
+>r1 : Symbol(r1, Decl(intersectionReduction.ts, 70, 3))
+>f10 : Symbol(f10, Decl(intersectionReduction.ts, 63, 37))
+>a1 : Symbol(a1, Decl(intersectionReduction.ts, 67, 11))
 
 let r2 = f10(a2);  // string
->r2 : Symbol(r2, Decl(intersectionReduction.ts, 70, 3))
->f10 : Symbol(f10, Decl(intersectionReduction.ts, 62, 37))
->a2 : Symbol(a2, Decl(intersectionReduction.ts, 67, 11))
+>r2 : Symbol(r2, Decl(intersectionReduction.ts, 71, 3))
+>f10 : Symbol(f10, Decl(intersectionReduction.ts, 63, 37))
+>a2 : Symbol(a2, Decl(intersectionReduction.ts, 68, 11))
 
 // Repro from #31663
 
 const x1 = { a: 'foo', b: 42 };
->x1 : Symbol(x1, Decl(intersectionReduction.ts, 74, 5))
->a : Symbol(a, Decl(intersectionReduction.ts, 74, 12))
->b : Symbol(b, Decl(intersectionReduction.ts, 74, 22))
-
-const x2 = { a: 'foo', b: true };
->x2 : Symbol(x2, Decl(intersectionReduction.ts, 75, 5))
+>x1 : Symbol(x1, Decl(intersectionReduction.ts, 75, 5))
 >a : Symbol(a, Decl(intersectionReduction.ts, 75, 12))
 >b : Symbol(b, Decl(intersectionReduction.ts, 75, 22))
 
+const x2 = { a: 'foo', b: true };
+>x2 : Symbol(x2, Decl(intersectionReduction.ts, 76, 5))
+>a : Symbol(a, Decl(intersectionReduction.ts, 76, 12))
+>b : Symbol(b, Decl(intersectionReduction.ts, 76, 22))
+
 declare let k: 'a' | 'b';
->k : Symbol(k, Decl(intersectionReduction.ts, 77, 11))
+>k : Symbol(k, Decl(intersectionReduction.ts, 78, 11))
 
 x1[k] = 'bar' as any;  // Error
->x1 : Symbol(x1, Decl(intersectionReduction.ts, 74, 5))
->k : Symbol(k, Decl(intersectionReduction.ts, 77, 11))
+>x1 : Symbol(x1, Decl(intersectionReduction.ts, 75, 5))
+>k : Symbol(k, Decl(intersectionReduction.ts, 78, 11))
 
 x2[k] = 'bar' as any;  // Error
->x2 : Symbol(x2, Decl(intersectionReduction.ts, 75, 5))
->k : Symbol(k, Decl(intersectionReduction.ts, 77, 11))
+>x2 : Symbol(x2, Decl(intersectionReduction.ts, 76, 5))
+>k : Symbol(k, Decl(intersectionReduction.ts, 78, 11))
 
 const enum Tag1 {}
->Tag1 : Symbol(Tag1, Decl(intersectionReduction.ts, 80, 21))
+>Tag1 : Symbol(Tag1, Decl(intersectionReduction.ts, 81, 21))
 
 const enum Tag2 {}
->Tag2 : Symbol(Tag2, Decl(intersectionReduction.ts, 82, 18))
+>Tag2 : Symbol(Tag2, Decl(intersectionReduction.ts, 83, 18))
 
 declare let s1: string & Tag1;
->s1 : Symbol(s1, Decl(intersectionReduction.ts, 85, 11))
->Tag1 : Symbol(Tag1, Decl(intersectionReduction.ts, 80, 21))
+>s1 : Symbol(s1, Decl(intersectionReduction.ts, 86, 11))
+>Tag1 : Symbol(Tag1, Decl(intersectionReduction.ts, 81, 21))
 
 declare let s2: string & Tag2;
->s2 : Symbol(s2, Decl(intersectionReduction.ts, 86, 11))
->Tag2 : Symbol(Tag2, Decl(intersectionReduction.ts, 82, 18))
+>s2 : Symbol(s2, Decl(intersectionReduction.ts, 87, 11))
+>Tag2 : Symbol(Tag2, Decl(intersectionReduction.ts, 83, 18))
 
 declare let t1: string & Tag1 | undefined;
->t1 : Symbol(t1, Decl(intersectionReduction.ts, 88, 11))
->Tag1 : Symbol(Tag1, Decl(intersectionReduction.ts, 80, 21))
+>t1 : Symbol(t1, Decl(intersectionReduction.ts, 89, 11))
+>Tag1 : Symbol(Tag1, Decl(intersectionReduction.ts, 81, 21))
 
 declare let t2: string & Tag2 | undefined;
->t2 : Symbol(t2, Decl(intersectionReduction.ts, 89, 11))
->Tag2 : Symbol(Tag2, Decl(intersectionReduction.ts, 82, 18))
+>t2 : Symbol(t2, Decl(intersectionReduction.ts, 90, 11))
+>Tag2 : Symbol(Tag2, Decl(intersectionReduction.ts, 83, 18))
 
 s1 = s2;
->s1 : Symbol(s1, Decl(intersectionReduction.ts, 85, 11))
->s2 : Symbol(s2, Decl(intersectionReduction.ts, 86, 11))
+>s1 : Symbol(s1, Decl(intersectionReduction.ts, 86, 11))
+>s2 : Symbol(s2, Decl(intersectionReduction.ts, 87, 11))
 
 s2 = s1;
->s2 : Symbol(s2, Decl(intersectionReduction.ts, 86, 11))
->s1 : Symbol(s1, Decl(intersectionReduction.ts, 85, 11))
+>s2 : Symbol(s2, Decl(intersectionReduction.ts, 87, 11))
+>s1 : Symbol(s1, Decl(intersectionReduction.ts, 86, 11))
 
 t1 = t2;
->t1 : Symbol(t1, Decl(intersectionReduction.ts, 88, 11))
->t2 : Symbol(t2, Decl(intersectionReduction.ts, 89, 11))
+>t1 : Symbol(t1, Decl(intersectionReduction.ts, 89, 11))
+>t2 : Symbol(t2, Decl(intersectionReduction.ts, 90, 11))
 
 t2 = t1;
->t2 : Symbol(t2, Decl(intersectionReduction.ts, 89, 11))
->t1 : Symbol(t1, Decl(intersectionReduction.ts, 88, 11))
+>t2 : Symbol(t2, Decl(intersectionReduction.ts, 90, 11))
+>t1 : Symbol(t1, Decl(intersectionReduction.ts, 89, 11))
 
 // Repro from #36736
 
 const f1 = (t: "a" | ("b" & "c")): "a" => t;
->f1 : Symbol(f1, Decl(intersectionReduction.ts, 99, 5))
->t : Symbol(t, Decl(intersectionReduction.ts, 99, 12))
->t : Symbol(t, Decl(intersectionReduction.ts, 99, 12))
+>f1 : Symbol(f1, Decl(intersectionReduction.ts, 100, 5))
+>t : Symbol(t, Decl(intersectionReduction.ts, 100, 12))
+>t : Symbol(t, Decl(intersectionReduction.ts, 100, 12))
 
 type Container<Type extends string> = {
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->Type : Symbol(Type, Decl(intersectionReduction.ts, 101, 15))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>Type : Symbol(Type, Decl(intersectionReduction.ts, 102, 15))
 
     type: Type;
->type : Symbol(type, Decl(intersectionReduction.ts, 101, 39))
->Type : Symbol(Type, Decl(intersectionReduction.ts, 101, 15))
+>type : Symbol(type, Decl(intersectionReduction.ts, 102, 39))
+>Type : Symbol(Type, Decl(intersectionReduction.ts, 102, 15))
 }
 
 const f2 = (t: Container<"a"> | (Container<"b"> & Container<"c">)): Container<"a"> => t;
->f2 : Symbol(f2, Decl(intersectionReduction.ts, 105, 5))
->t : Symbol(t, Decl(intersectionReduction.ts, 105, 12))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->t : Symbol(t, Decl(intersectionReduction.ts, 105, 12))
+>f2 : Symbol(f2, Decl(intersectionReduction.ts, 106, 5))
+>t : Symbol(t, Decl(intersectionReduction.ts, 106, 12))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>t : Symbol(t, Decl(intersectionReduction.ts, 106, 12))
 
 const f3 = (t: Container<"a"> | (Container<"b"> & { dataB: boolean } & Container<"a">)): Container<"a"> => t;
->f3 : Symbol(f3, Decl(intersectionReduction.ts, 106, 5))
->t : Symbol(t, Decl(intersectionReduction.ts, 106, 12))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->dataB : Symbol(dataB, Decl(intersectionReduction.ts, 106, 51))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->t : Symbol(t, Decl(intersectionReduction.ts, 106, 12))
+>f3 : Symbol(f3, Decl(intersectionReduction.ts, 107, 5))
+>t : Symbol(t, Decl(intersectionReduction.ts, 107, 12))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>dataB : Symbol(dataB, Decl(intersectionReduction.ts, 107, 51))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>t : Symbol(t, Decl(intersectionReduction.ts, 107, 12))
 
 const f4 = (t: number | (Container<"b"> & { dataB: boolean } & Container<"a">)): number => t;
->f4 : Symbol(f4, Decl(intersectionReduction.ts, 107, 5))
->t : Symbol(t, Decl(intersectionReduction.ts, 107, 12))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->dataB : Symbol(dataB, Decl(intersectionReduction.ts, 107, 43))
->Container : Symbol(Container, Decl(intersectionReduction.ts, 99, 44))
->t : Symbol(t, Decl(intersectionReduction.ts, 107, 12))
+>f4 : Symbol(f4, Decl(intersectionReduction.ts, 108, 5))
+>t : Symbol(t, Decl(intersectionReduction.ts, 108, 12))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>dataB : Symbol(dataB, Decl(intersectionReduction.ts, 108, 43))
+>Container : Symbol(Container, Decl(intersectionReduction.ts, 100, 44))
+>t : Symbol(t, Decl(intersectionReduction.ts, 108, 12))
 

tests/baselines/reference/intersectionReduction.types

@@ -111,6 +111,11 @@ ab.kind;  // Error
 >ab : never
 >kind : any
 
+ab = 42;
+>ab = 42 : 42
+>ab : never
+>42 : 42
+
 declare let x: A | (B & C);  // A
 >x : A
 

tests/baselines/reference/intersectionReductionStrict.errors.txt

@@ -1,4 +1,5 @@
 tests/cases/conformance/types/intersection/intersectionReductionStrict.ts(38,4): error TS2339: Property 'kind' does not exist on type 'never'.
+  The type 'never' was reduced from the intersection 'A & B'. Each type of that intersection has properties that conflict, so values of that type can never exist.
 tests/cases/conformance/types/intersection/intersectionReductionStrict.ts(69,1): error TS2322: Type 'any' is not assignable to type 'never'.
 tests/cases/conformance/types/intersection/intersectionReductionStrict.ts(70,1): error TS2322: Type 'any' is not assignable to type 'never'.
 
@@ -44,6 +45,7 @@ tests/cases/conformance/types/intersection/intersectionReductionStrict.ts(70,1):
     ab.kind;  // Error
        ~~~~
 !!! error TS2339: Property 'kind' does not exist on type 'never'.
+!!! error TS2339:   The type 'never' was reduced from the intersection 'A & B'. Each type of that intersection has properties that conflict, so values of that type can never exist.
     
     declare let x: A | (B & C);  // A
     let a: A = x;

tests/baselines/reference/typeGuardsWithInstanceOf.errors.txt

@@ -1,4 +1,5 @@
 tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts(7,20): error TS2339: Property 'global' does not exist on type 'never'.
+  The type 'never' was reduced from the intersection 'I & RegExp'. Each type of that intersection has properties that conflict, so values of that type can never exist.
 
 
 ==== tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts (1 errors) ====
@@ -11,4 +12,5 @@ tests/cases/conformance/expressions/typeGuards/typeGuardsWithInstanceOf.ts(7,20)
     } else if (!result.global) {
                        ~~~~~~
 !!! error TS2339: Property 'global' does not exist on type 'never'.
+!!! error TS2339:   The type 'never' was reduced from the intersection 'I & RegExp'. Each type of that intersection has properties that conflict, so values of that type can never exist.
     }