Ignore constraints of generic mapped types in definitelyAssignableRelation

ahejlsberg · ahejlsberg · commit 056c87f289d5 · 2018-08-22T07:08:35.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -11778,6 +11778,9 @@ namespace ts {
                         }
                         return Ternary.False;
                     }
+                    if (relation === definitelyAssignableRelation && isGenericMappedType(source)) {
+                        return Ternary.False;
+                    }
                     const sourceIsPrimitive = !!(source.flags & TypeFlags.Primitive);
                     if (relation !== identityRelation) {
                         source = getApparentType(source);

Original file line number	Diff line number	Diff line change
`@@ -11778,6 +11778,9 @@ namespace ts {`
`11778`	`11778`	`}`
`11779`	`11779`	`return Ternary.False;`
`11780`	`11780`	`}`
	`11781`	`+ if (relation === definitelyAssignableRelation && isGenericMappedType(source)) {`
	`11782`	`+ return Ternary.False;`
	`11783`	`+ }`
`11781`	`11784`	`const sourceIsPrimitive = !!(source.flags & TypeFlags.Primitive);`
`11782`	`11785`	`if (relation !== identityRelation) {`
`11783`	`11786`	`source = getApparentType(source);`