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Merge pull request #20882 from Microsoft/fixNarrowTypeBySwitch

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Fix narrowing of type variable in switch statement
This commit is contained in:
Anders Hejlsberg
2017-12-28 09:22:26 -08:00
committed by GitHub
parent 9e9d7d57fa d1befefab9
commit ff4f03c51d
5 changed files with 105 additions and 1 deletions
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src/compiler/checker.ts
+1 -1
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@@ -12923,7 +12923,7 @@ namespace ts {
const discriminantType = getUnionType(clauseTypes);
const caseType =
discriminantType.flags & TypeFlags.Never ? neverType :
replacePrimitivesWithLiterals(filterType(type, t => isTypeComparableTo(discriminantType, t)), discriminantType);
replacePrimitivesWithLiterals(filterType(type, t => areTypesComparable(discriminantType, t)), discriminantType);
if (!hasDefaultClause) {
return caseType;
}
tests/baselines/reference/switchWithConstrainedTypeVariable.js
+28
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@@ -0,0 +1,28 @@
//// [switchWithConstrainedTypeVariable.ts]
// Repro from #20840
function function1<T extends 'a' | 'b'>(key: T) {
switch (key) {
case 'a':
key.toLowerCase();
break;
default:
key.toLowerCase();
break;
}
}
//// [switchWithConstrainedTypeVariable.js]
"use strict";
// Repro from #20840
function function1(key) {
switch (key) {
case 'a':
key.toLowerCase();
break;
default:
key.toLowerCase();
break;
}
}
tests/baselines/reference/switchWithConstrainedTypeVariable.symbols
+29
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@@ -0,0 +1,29 @@
=== tests/cases/conformance/controlFlow/switchWithConstrainedTypeVariable.ts ===
// Repro from #20840
function function1<T extends 'a' | 'b'>(key: T) {
>function1 : Symbol(function1, Decl(switchWithConstrainedTypeVariable.ts, 0, 0))
>T : Symbol(T, Decl(switchWithConstrainedTypeVariable.ts, 2, 19))
>key : Symbol(key, Decl(switchWithConstrainedTypeVariable.ts, 2, 40))
>T : Symbol(T, Decl(switchWithConstrainedTypeVariable.ts, 2, 19))
switch (key) {
>key : Symbol(key, Decl(switchWithConstrainedTypeVariable.ts, 2, 40))
case 'a':
key.toLowerCase();
>key.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
>key : Symbol(key, Decl(switchWithConstrainedTypeVariable.ts, 2, 40))
>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
break;
default:
key.toLowerCase();
>key.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
>key : Symbol(key, Decl(switchWithConstrainedTypeVariable.ts, 2, 40))
>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
break;
}
}
tests/baselines/reference/switchWithConstrainedTypeVariable.types
+33
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@@ -0,0 +1,33 @@
=== tests/cases/conformance/controlFlow/switchWithConstrainedTypeVariable.ts ===
// Repro from #20840
function function1<T extends 'a' | 'b'>(key: T) {
>function1 : <T extends "a" | "b">(key: T) => void
>T : T
>key : T
>T : T
switch (key) {
>key : T
case 'a':
>'a' : "a"
key.toLowerCase();
>key.toLowerCase() : string
>key.toLowerCase : () => string
>key : T
>toLowerCase : () => string
break;
default:
key.toLowerCase();
>key.toLowerCase() : string
>key.toLowerCase : () => string
>key : T
>toLowerCase : () => string
break;
}
}
tests/cases/conformance/controlFlow/switchWithConstrainedTypeVariable.ts
+14
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@@ -0,0 +1,14 @@
// @strict: true
// Repro from #20840
function function1<T extends 'a' | 'b'>(key: T) {
switch (key) {
case 'a':
key.toLowerCase();
break;
default:
key.toLowerCase();
break;
}
}