Simplify mapped-type handling in computeBaseConstraint

sandersn · sandersn · commit a187b17e97fe · 2017-08-17T13:09:21.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -5968,7 +5968,7 @@ namespace ts {
             function computeBaseConstraint(t: Type): Type {
                 if (t.flags & TypeFlags.TypeParameter) {
                     const constraint = getConstraintFromTypeParameter(<TypeParameter>t);
-                    return ((t as TypeParameter).isThisType || !constraint || getObjectFlags(constraint) & ObjectFlags.Mapped) ?
+                    return (t as TypeParameter).isThisType || !constraint ?
                         constraint :
                         getBaseConstraint(constraint);
                 }
@@ -5998,9 +5998,6 @@ namespace ts {
                     const baseIndexedAccess = baseObjectType && baseIndexType ? getIndexedAccessType(baseObjectType, baseIndexType) : undefined;
                     return baseIndexedAccess && baseIndexedAccess !== unknownType ? getBaseConstraint(baseIndexedAccess) : undefined;
                 }
-                if (isGenericMappedType(t)) {
-                    return emptyObjectType;
-                }
                 return t;
             }
         }

Original file line number	Diff line number	Diff line change
`@@ -5968,7 +5968,7 @@ namespace ts {`
`5968`	`5968`	`function computeBaseConstraint(t: Type): Type {`
`5969`	`5969`	`if (t.flags & TypeFlags.TypeParameter) {`
`5970`	`5970`	`const constraint = getConstraintFromTypeParameter(<TypeParameter>t);`
`5971`		`- return ((t as TypeParameter).isThisType \|\| !constraint \|\| getObjectFlags(constraint) & ObjectFlags.Mapped) ?`
	`5971`	`+ return (t as TypeParameter).isThisType \|\| !constraint ?`
`5972`	`5972`	`constraint :`
`5973`	`5973`	`getBaseConstraint(constraint);`
`5974`	`5974`	`}`
`@@ -5998,9 +5998,6 @@ namespace ts {`
`5998`	`5998`	`const baseIndexedAccess = baseObjectType && baseIndexType ? getIndexedAccessType(baseObjectType, baseIndexType) : undefined;`
`5999`	`5999`	`return baseIndexedAccess && baseIndexedAccess !== unknownType ? getBaseConstraint(baseIndexedAccess) : undefined;`
`6000`	`6000`	`}`
`6001`		`- if (isGenericMappedType(t)) {`
`6002`		`- return emptyObjectType;`
`6003`		`- }`
`6004`	`6001`	`return t;`
`6005`	`6002`	`}`
`6006`	`6003`	`}`