Properly instantiate true type when extends type is any or unknown

ahejlsberg · ahejlsberg · commit 5a567ad56dac · 2019-04-27T09:56:01.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -10383,7 +10383,7 @@ namespace ts {
             // We attempt to resolve the conditional type only when the check and extends types are non-generic
             if (!checkTypeInstantiable && !maybeTypeOfKind(inferredExtendsType, TypeFlags.Instantiable | TypeFlags.GenericMappedType)) {
                 if (inferredExtendsType.flags & TypeFlags.AnyOrUnknown) {
-                    return trueType;
+                    return instantiateType(root.trueType, combinedMapper || mapper);
                 }
                 // Return union of trueType and falseType for 'any' since it matches anything
                 if (checkType.flags & TypeFlags.Any) {

Original file line number	Diff line number	Diff line change
`@@ -10383,7 +10383,7 @@ namespace ts {`
`10383`	`10383`	`// We attempt to resolve the conditional type only when the check and extends types are non-generic`
`10384`	`10384`	`if (!checkTypeInstantiable && !maybeTypeOfKind(inferredExtendsType, TypeFlags.Instantiable \| TypeFlags.GenericMappedType)) {`
`10385`	`10385`	`if (inferredExtendsType.flags & TypeFlags.AnyOrUnknown) {`
`10386`		`- return trueType;`
	`10386`	`+ return instantiateType(root.trueType, combinedMapper \|\| mapper);`
`10387`	`10387`	`}`
`10388`	`10388`	`// Return union of trueType and falseType for 'any' since it matches anything`
`10389`	`10389`	`if (checkType.flags & TypeFlags.Any) {`