Fix narrowTypeBySwitchOnDiscriminant function

ahejlsberg · ahejlsberg · commit 5d3ecaebadf7 · 2017-12-23T19:12:49.000-08:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -12914,7 +12914,7 @@ 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;
                 }

Original file line number	Diff line number	Diff line change
`@@ -12914,7 +12914,7 @@ namespace ts {`
`12914`	`12914`	`const discriminantType = getUnionType(clauseTypes);`
`12915`	`12915`	`const caseType =`
`12916`	`12916`	`discriminantType.flags & TypeFlags.Never ? neverType :`
`12917`		`- replacePrimitivesWithLiterals(filterType(type, t => isTypeComparableTo(discriminantType, t)), discriminantType);`
	`12917`	`+ replacePrimitivesWithLiterals(filterType(type, t => areTypesComparable(discriminantType, t)), discriminantType);`
`12918`	`12918`	`if (!hasDefaultClause) {`
`12919`	`12919`	`return caseType;`
`12920`	`12920`	`}`