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ahejlsbergahejlsberg
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Merge pull request microsoft#16446 from Microsoft/fixNeverIntersection
Intersection with 'never' is always 'never'
2 parents a404eda + a74b790 commit fd1edd2

5 files changed

Lines changed: 119 additions & 1 deletion

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‎src/compiler/checker.ts‎

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7168,6 +7168,7 @@ namespace ts {
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containsAny?: boolean;
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containsUndefined?: boolean;
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containsNull?: boolean;
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containsNever?: boolean;
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containsNonWideningType?: boolean;
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containsString?: boolean;
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containsNumber?: boolean;
@@ -7369,10 +7370,13 @@ namespace ts {
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else if (type.flags & TypeFlags.Any) {
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typeSet.containsAny = true;
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}
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else if (type.flags & TypeFlags.Never) {
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typeSet.containsNever = true;
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}
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else if (getObjectFlags(type) & ObjectFlags.Anonymous && isEmptyObjectType(type)) {
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typeSet.containsEmptyObject = true;
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}
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else if (!(type.flags & TypeFlags.Never) && (strictNullChecks || !(type.flags & TypeFlags.Nullable)) && !contains(typeSet, type)) {
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else if ((strictNullChecks || !(type.flags & TypeFlags.Nullable)) && !contains(typeSet, type)) {
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if (type.flags & TypeFlags.Object) {
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typeSet.containsObjectType = true;
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}
@@ -7410,6 +7414,9 @@ namespace ts {
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}
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const typeSet = [] as TypeSet;
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addTypesToIntersection(typeSet, types);
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if (typeSet.containsNever) {
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return neverType;
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}
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if (typeSet.containsAny) {
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return anyType;
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}

‎tests/baselines/reference/neverUnionIntersection.js‎

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@@ -0,0 +1,17 @@
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//// [neverUnionIntersection.ts]
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type T01 = string | never;
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type T02 = string & never;
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type T03 = string | number | never;
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type T04 = string & number & never;
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type T05 = any | never;
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type T06 = any & never;
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type T07 = undefined | never;
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type T08 = undefined & never;
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type T09 = null | never;
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type T10 = null & never;
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type T11 = { a: string } | never;
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type T12 = { a: string } & never;
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//// [neverUnionIntersection.js]
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"use strict";

‎tests/baselines/reference/neverUnionIntersection.symbols‎

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@@ -0,0 +1,39 @@
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=== tests/cases/conformance/types/never/neverUnionIntersection.ts ===
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type T01 = string | never;
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>T01 : Symbol(T01, Decl(neverUnionIntersection.ts, 0, 0))
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type T02 = string & never;
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>T02 : Symbol(T02, Decl(neverUnionIntersection.ts, 0, 26))
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type T03 = string | number | never;
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>T03 : Symbol(T03, Decl(neverUnionIntersection.ts, 1, 26))
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type T04 = string & number & never;
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>T04 : Symbol(T04, Decl(neverUnionIntersection.ts, 2, 35))
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type T05 = any | never;
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>T05 : Symbol(T05, Decl(neverUnionIntersection.ts, 3, 35))
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type T06 = any & never;
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>T06 : Symbol(T06, Decl(neverUnionIntersection.ts, 4, 23))
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type T07 = undefined | never;
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>T07 : Symbol(T07, Decl(neverUnionIntersection.ts, 5, 23))
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type T08 = undefined & never;
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>T08 : Symbol(T08, Decl(neverUnionIntersection.ts, 6, 29))
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type T09 = null | never;
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>T09 : Symbol(T09, Decl(neverUnionIntersection.ts, 7, 29))
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type T10 = null & never;
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>T10 : Symbol(T10, Decl(neverUnionIntersection.ts, 8, 24))
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type T11 = { a: string } | never;
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>T11 : Symbol(T11, Decl(neverUnionIntersection.ts, 9, 24))
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>a : Symbol(a, Decl(neverUnionIntersection.ts, 10, 12))
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type T12 = { a: string } & never;
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>T12 : Symbol(T12, Decl(neverUnionIntersection.ts, 10, 33))
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>a : Symbol(a, Decl(neverUnionIntersection.ts, 11, 12))
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‎tests/baselines/reference/neverUnionIntersection.types‎

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@@ -0,0 +1,41 @@
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=== tests/cases/conformance/types/never/neverUnionIntersection.ts ===
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type T01 = string | never;
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>T01 : string
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type T02 = string & never;
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>T02 : never
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type T03 = string | number | never;
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>T03 : T03
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type T04 = string & number & never;
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>T04 : never
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type T05 = any | never;
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>T05 : any
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type T06 = any & never;
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>T06 : never
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type T07 = undefined | never;
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>T07 : undefined
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type T08 = undefined & never;
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>T08 : never
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type T09 = null | never;
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>T09 : null
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>null : null
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type T10 = null & never;
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>T10 : never
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>null : null
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type T11 = { a: string } | never;
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>T11 : { a: string; }
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>a : string
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type T12 = { a: string } & never;
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>T12 : never
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>a : string
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‎tests/cases/conformance/types/never/neverUnionIntersection.ts‎

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@@ -0,0 +1,14 @@
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// @strict: true
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type T01 = string | never;
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type T02 = string & never;
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type T03 = string | number | never;
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type T04 = string & number & never;
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type T05 = any | never;
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type T06 = any & never;
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type T07 = undefined | never;
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type T08 = undefined & never;
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type T09 = null | never;
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type T10 = null & never;
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type T11 = { a: string } | never;
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type T12 = { a: string } & never;

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