Avoid elaborating object literals against array-likes

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) {

tests/baselines/reference/objectLiteralsAgainstUnionsOfArrays01.errors.txt

@@ -0,0 +1,30 @@
+tests/cases/compiler/objectLiteralsAgainstUnionsOfArrays01.ts(9,5): error TS2322: Type '{ bar: { prop: number; }; }[]' is not assignable to type 'Foo[]'.
+  Type '{ bar: { prop: number; }; }' is not assignable to type 'Foo'.
+    Types of property 'bar' are incompatible.
+      Type '{ prop: number; }' is not assignable to type 'Bar | Bar[]'.
+        Type '{ prop: number; }' is not assignable to type 'Bar'.
+          Types of property 'prop' are incompatible.
+            Type 'number' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/objectLiteralsAgainstUnionsOfArrays01.ts (1 errors) ====
+    interface Foo {
+      bar: Bar | Bar[];
+    }
+
+    interface Bar {
+      prop: string;
+    }
+
+    let x: Foo[] = [
+        ~
+!!! error TS2322: Type '{ bar: { prop: number; }; }[]' is not assignable to type 'Foo[]'.
+!!! error TS2322:   Type '{ bar: { prop: number; }; }' is not assignable to type 'Foo'.
+!!! error TS2322:     Types of property 'bar' are incompatible.
+!!! error TS2322:       Type '{ prop: number; }' is not assignable to type 'Bar | Bar[]'.
+!!! error TS2322:         Type '{ prop: number; }' is not assignable to type 'Bar'.
+!!! error TS2322:           Types of property 'prop' are incompatible.
+!!! error TS2322:             Type 'number' is not assignable to type 'string'.
+      { bar: { prop: 100 } }
+    ]
+

tests/baselines/reference/objectLiteralsAgainstUnionsOfArrays01.js

@@ -0,0 +1,18 @@
+//// [objectLiteralsAgainstUnionsOfArrays01.ts]
+interface Foo {
+  bar: Bar | Bar[];
+}
+
+interface Bar {
+  prop: string;
+}
+
+let x: Foo[] = [
+  { bar: { prop: 100 } }
+]
+
+
+//// [objectLiteralsAgainstUnionsOfArrays01.js]
+var x = [
+    { bar: { prop: 100 } }
+];

tests/baselines/reference/objectLiteralsAgainstUnionsOfArrays01.symbols

@@ -0,0 +1,27 @@
+=== tests/cases/compiler/objectLiteralsAgainstUnionsOfArrays01.ts ===
+interface Foo {
+>Foo : Symbol(Foo, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 0, 0))
+
+  bar: Bar | Bar[];
+>bar : Symbol(Foo.bar, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 0, 15))
+>Bar : Symbol(Bar, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 2, 1))
+>Bar : Symbol(Bar, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 2, 1))
+}
+
+interface Bar {
+>Bar : Symbol(Bar, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 2, 1))
+
+  prop: string;
+>prop : Symbol(Bar.prop, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 4, 15))
+}
+
+let x: Foo[] = [
+>x : Symbol(x, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 8, 3))
+>Foo : Symbol(Foo, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 0, 0))
+
+  { bar: { prop: 100 } }
+>bar : Symbol(bar, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 9, 3))
+>prop : Symbol(prop, Decl(objectLiteralsAgainstUnionsOfArrays01.ts, 9, 10))
+
+]
+

tests/baselines/reference/objectLiteralsAgainstUnionsOfArrays01.types

@@ -0,0 +1,31 @@
+=== tests/cases/compiler/objectLiteralsAgainstUnionsOfArrays01.ts ===
+interface Foo {
+>Foo : Foo
+
+  bar: Bar | Bar[];
+>bar : Bar | Bar[]
+>Bar : Bar
+>Bar : Bar
+}
+
+interface Bar {
+>Bar : Bar
+
+  prop: string;
+>prop : string
+}
+
+let x: Foo[] = [
+>x : Foo[]
+>Foo : Foo
+>[  { bar: { prop: 100 } }] : { bar: { prop: number; }; }[]
+
+  { bar: { prop: 100 } }
+>{ bar: { prop: 100 } } : { bar: { prop: number; }; }
+>bar : { prop: number; }
+>{ prop: 100 } : { prop: number; }
+>prop : number
+>100 : 100
+
+]
+

tests/cases/compiler/objectLiteralsAgainstUnionsOfArrays01.ts

@@ -0,0 +1,11 @@
+interface Foo {
+  bar: Bar | Bar[];
+}
+
+interface Bar {
+  prop: string;
+}
+
+let x: Foo[] = [
+  { bar: { prop: 100 } }
+]