Elaborate on the first non-array type when object literals are compared against 'T | T[]'.

DanielRosenwasser · DanielRosenwasser · commit 649f2944137b · 2018-07-17T21:54:33.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -11182,7 +11182,8 @@ namespace ts {
                 if (reportErrors) {
                     const bestMatchingType =
                         findMatchingDiscriminantType(source, target) ||
-                        findMatchingTypeReferenceOrTypeAliasReference(source, target);
+                        findMatchingTypeReferenceOrTypeAliasReference(source, target) ||
+                        findBestTypeForObjectLiteral(source, target);
 
                     isRelatedTo(source, bestMatchingType || targetTypes[targetTypes.length - 1], /*reportErrors*/ true);
                 }
@@ -11207,6 +11208,11 @@ namespace ts {
                 }
             }
 
+            function findBestTypeForObjectLiteral(source: Type, unionTarget: UnionOrIntersectionType) {
+                if (getObjectFlags(source) & ObjectFlags.ObjectLiteral && forEachType(unionTarget, isArrayLikeType)) {
+                    return find(unionTarget.types, t => !isArrayLikeType(t));
+                }
+            }
 
             // Keep this up-to-date with the same logic within `getApparentTypeOfContextualType`, since they should behave similarly
             function findMatchingDiscriminantType(source: Type, target: UnionOrIntersectionType) {

Original file line number	Diff line number	Diff line change
`@@ -11182,7 +11182,8 @@ namespace ts {`
`11182`	`11182`	`if (reportErrors) {`
`11183`	`11183`	`const bestMatchingType =`
`11184`	`11184`	`findMatchingDiscriminantType(source, target) \|\|`
`11185`		`- findMatchingTypeReferenceOrTypeAliasReference(source, target);`
	`11185`	`+ findMatchingTypeReferenceOrTypeAliasReference(source, target) \|\|`
	`11186`	`+ findBestTypeForObjectLiteral(source, target);`
`11186`	`11187`
`11187`	`11188`	`isRelatedTo(source, bestMatchingType \|\| targetTypes[targetTypes.length - 1], /reportErrors/ true);`
`11188`	`11189`	`}`
`@@ -11207,6 +11208,11 @@ namespace ts {`
`11207`	`11208`	`}`
`11208`	`11209`	`}`
`11209`	`11210`
	`11211`	`+ function findBestTypeForObjectLiteral(source: Type, unionTarget: UnionOrIntersectionType) {`
	`11212`	`+ if (getObjectFlags(source) & ObjectFlags.ObjectLiteral && forEachType(unionTarget, isArrayLikeType)) {`
	`11213`	`+ return find(unionTarget.types, t => !isArrayLikeType(t));`
	`11214`	`+ }`
	`11215`	`+ }`
`11210`	`11216`
`11211`	`11217`	// Keep this up-to-date with the same logic within `getApparentTypeOfContextualType`, since they should behave similarly
`11212`	`11218`	`function findMatchingDiscriminantType(source: Type, target: UnionOrIntersectionType) {`