Use removeDefinitelyFalsyTypes for building partial type

src/compiler/checker.ts

@@ -7923,15 +7923,10 @@ namespace ts {
 
         function getPartialTypeFromFalsyUnion(type: UnionType): Type | undefined {
             if (type.types.length === 2) {
-                // getFalsyFlagsOfTypes
-                // getTypeFacts
-                const i = Math.max(type.types.indexOf(falseType),
-                         type.types.indexOf(zeroType),
-                         type.types.indexOf(emptyStringType));
-                if (i > -1) {
+                const truthy = removeDefinitelyFalsyTypes(type);
+                if (truthy !== type) {
                     const members = createSymbolTable();
-                    const other = type.types[i === 0 ? 1 : 0];
-                    for (const prop of getPropertiesOfType(other)) {
+                    for (const prop of getPropertiesOfType(truthy)) {
                         if (prop.flags & SymbolFlags.Optional) {
                             members.set(prop.escapedName, prop);
                         }
@@ -7943,7 +7938,7 @@ namespace ts {
                             members.set(prop.escapedName, result);
                         }
                     }
-                    return createAnonymousType(undefined, members, emptyArray, emptyArray, getIndexInfoOfType(other, IndexKind.String), getIndexInfoOfType(other, IndexKind.Number));
+                    return createAnonymousType(undefined, members, emptyArray, emptyArray, getIndexInfoOfType(truthy, IndexKind.String), getIndexInfoOfType(truthy, IndexKind.Number));
                 }
             }
         }

tests/baselines/reference/spreadUnion2.js

@@ -3,20 +3,20 @@ declare const undefinedUnion: { a: number } | undefined;
 declare const nullUnion: { b: number } | null;
 declare const nullAndUndefinedUnion: null | undefined;
 
-var o1: {} | { a: number };
+var o1: { a?: number | undefined };
 var o1 = { ...undefinedUnion };
 
-var o2: {} | { b: number };
+var o2: { b?: number | undefined };
 var o2 = { ...nullUnion };
 
-var o3: {} | { b: number } | { a: number } | { a: number, b: number };
+var o3: { a?: number | undefined, b?: number | undefined };
 var o3 = { ...undefinedUnion, ...nullUnion };
 var o3 = { ...nullUnion, ...undefinedUnion };
 
-var o4: {} | { a: number };
+var o4: { a?: number | undefined };
 var o4 = { ...undefinedUnion, ...undefinedUnion };
 
-var o5: {} | { b: number };
+var o5: { b?: number | undefined };
 var o5 = { ...nullUnion, ...nullUnion };
 
 var o6 = { ...nullAndUndefinedUnion, ...nullAndUndefinedUnion };

tests/baselines/reference/spreadUnion2.symbols

@@ -10,28 +10,26 @@ declare const nullUnion: { b: number } | null;
 declare const nullAndUndefinedUnion: null | undefined;
 >nullAndUndefinedUnion : Symbol(nullAndUndefinedUnion, Decl(spreadUnion2.ts, 2, 13))
 
-var o1: {} | { a: number };
+var o1: { a?: number | undefined };
 >o1 : Symbol(o1, Decl(spreadUnion2.ts, 4, 3), Decl(spreadUnion2.ts, 5, 3))
->a : Symbol(a, Decl(spreadUnion2.ts, 4, 14))
+>a : Symbol(a, Decl(spreadUnion2.ts, 4, 9))
 
 var o1 = { ...undefinedUnion };
 >o1 : Symbol(o1, Decl(spreadUnion2.ts, 4, 3), Decl(spreadUnion2.ts, 5, 3))
 >undefinedUnion : Symbol(undefinedUnion, Decl(spreadUnion2.ts, 0, 13))
 
-var o2: {} | { b: number };
+var o2: { b?: number | undefined };
 >o2 : Symbol(o2, Decl(spreadUnion2.ts, 7, 3), Decl(spreadUnion2.ts, 8, 3))
->b : Symbol(b, Decl(spreadUnion2.ts, 7, 14))
+>b : Symbol(b, Decl(spreadUnion2.ts, 7, 9))
 
 var o2 = { ...nullUnion };
 >o2 : Symbol(o2, Decl(spreadUnion2.ts, 7, 3), Decl(spreadUnion2.ts, 8, 3))
 >nullUnion : Symbol(nullUnion, Decl(spreadUnion2.ts, 1, 13))
 
-var o3: {} | { b: number } | { a: number } | { a: number, b: number };
+var o3: { a?: number | undefined, b?: number | undefined };
 >o3 : Symbol(o3, Decl(spreadUnion2.ts, 10, 3), Decl(spreadUnion2.ts, 11, 3), Decl(spreadUnion2.ts, 12, 3))
->b : Symbol(b, Decl(spreadUnion2.ts, 10, 14))
->a : Symbol(a, Decl(spreadUnion2.ts, 10, 30))
->a : Symbol(a, Decl(spreadUnion2.ts, 10, 46))
->b : Symbol(b, Decl(spreadUnion2.ts, 10, 57))
+>a : Symbol(a, Decl(spreadUnion2.ts, 10, 9))
+>b : Symbol(b, Decl(spreadUnion2.ts, 10, 33))
 
 var o3 = { ...undefinedUnion, ...nullUnion };
 >o3 : Symbol(o3, Decl(spreadUnion2.ts, 10, 3), Decl(spreadUnion2.ts, 11, 3), Decl(spreadUnion2.ts, 12, 3))
@@ -43,18 +41,18 @@ var o3 = { ...nullUnion, ...undefinedUnion };
 >nullUnion : Symbol(nullUnion, Decl(spreadUnion2.ts, 1, 13))
 >undefinedUnion : Symbol(undefinedUnion, Decl(spreadUnion2.ts, 0, 13))
 
-var o4: {} | { a: number };
+var o4: { a?: number | undefined };
 >o4 : Symbol(o4, Decl(spreadUnion2.ts, 14, 3), Decl(spreadUnion2.ts, 15, 3))
->a : Symbol(a, Decl(spreadUnion2.ts, 14, 14))
+>a : Symbol(a, Decl(spreadUnion2.ts, 14, 9))
 
 var o4 = { ...undefinedUnion, ...undefinedUnion };
 >o4 : Symbol(o4, Decl(spreadUnion2.ts, 14, 3), Decl(spreadUnion2.ts, 15, 3))
 >undefinedUnion : Symbol(undefinedUnion, Decl(spreadUnion2.ts, 0, 13))
 >undefinedUnion : Symbol(undefinedUnion, Decl(spreadUnion2.ts, 0, 13))
 
-var o5: {} | { b: number };
+var o5: { b?: number | undefined };
 >o5 : Symbol(o5, Decl(spreadUnion2.ts, 17, 3), Decl(spreadUnion2.ts, 18, 3))
->b : Symbol(b, Decl(spreadUnion2.ts, 17, 14))
+>b : Symbol(b, Decl(spreadUnion2.ts, 17, 9))
 
 var o5 = { ...nullUnion, ...nullUnion };
 >o5 : Symbol(o5, Decl(spreadUnion2.ts, 17, 3), Decl(spreadUnion2.ts, 18, 3))

tests/baselines/reference/spreadUnion2.types

@@ -12,71 +12,69 @@ declare const nullAndUndefinedUnion: null | undefined;
 >nullAndUndefinedUnion : null | undefined
 >null : null
 
-var o1: {} | { a: number };
->o1 : {} | { a: number; }
->a : number
+var o1: { a?: number | undefined };
+>o1 : { a?: number | undefined; }
+>a : number | undefined
 
 var o1 = { ...undefinedUnion };
->o1 : {} | { a: number; }
->{ ...undefinedUnion } : {} | { a: number; }
+>o1 : { a?: number | undefined; }
+>{ ...undefinedUnion } : { a?: number | undefined; }
 >undefinedUnion : { a: number; } | undefined
 
-var o2: {} | { b: number };
->o2 : {} | { b: number; }
->b : number
+var o2: { b?: number | undefined };
+>o2 : { b?: number | undefined; }
+>b : number | undefined
 
 var o2 = { ...nullUnion };
->o2 : {} | { b: number; }
->{ ...nullUnion } : {} | { b: number; }
+>o2 : { b?: number | undefined; }
+>{ ...nullUnion } : { b?: number | undefined; }
 >nullUnion : { b: number; } | null
 
-var o3: {} | { b: number } | { a: number } | { a: number, b: number };
->o3 : {} | { b: number; } | { a: number; } | { a: number; b: number; }
->b : number
->a : number
->a : number
->b : number
+var o3: { a?: number | undefined, b?: number | undefined };
+>o3 : { a?: number | undefined; b?: number | undefined; }
+>a : number | undefined
+>b : number | undefined
 
 var o3 = { ...undefinedUnion, ...nullUnion };
->o3 : {} | { b: number; } | { a: number; } | { a: number; b: number; }
->{ ...undefinedUnion, ...nullUnion } : {} | { b: number; } | { a: number; } | { b: number; a: number; }
+>o3 : { a?: number | undefined; b?: number | undefined; }
+>{ ...undefinedUnion, ...nullUnion } : { b?: number | undefined; a?: number | undefined; }
 >undefinedUnion : { a: number; } | undefined
 >nullUnion : { b: number; } | null
 
 var o3 = { ...nullUnion, ...undefinedUnion };
->o3 : {} | { b: number; } | { a: number; } | { a: number; b: number; }
->{ ...nullUnion, ...undefinedUnion } : {} | { a: number; } | { b: number; } | { a: number; b: number; }
+>o3 : { a?: number | undefined; b?: number | undefined; }
+>{ ...nullUnion, ...undefinedUnion } : { a?: number | undefined; b?: number | undefined; }
 >nullUnion : { b: number; } | null
 >undefinedUnion : { a: number; } | undefined
 
-var o4: {} | { a: number };
->o4 : {} | { a: number; }
->a : number
+var o4: { a?: number | undefined };
+>o4 : { a?: number | undefined; }
+>a : number | undefined
 
 var o4 = { ...undefinedUnion, ...undefinedUnion };
->o4 : {} | { a: number; }
->{ ...undefinedUnion, ...undefinedUnion } : {} | { a: number; } | { a: number; } | { a: number; }
+>o4 : { a?: number | undefined; }
+>{ ...undefinedUnion, ...undefinedUnion } : { a?: number | undefined; }
 >undefinedUnion : { a: number; } | undefined
 >undefinedUnion : { a: number; } | undefined
 
-var o5: {} | { b: number };
->o5 : {} | { b: number; }
->b : number
+var o5: { b?: number | undefined };
+>o5 : { b?: number | undefined; }
+>b : number | undefined
 
 var o5 = { ...nullUnion, ...nullUnion };
->o5 : {} | { b: number; }
->{ ...nullUnion, ...nullUnion } : {} | { b: number; } | { b: number; } | { b: number; }
+>o5 : { b?: number | undefined; }
+>{ ...nullUnion, ...nullUnion } : { b?: number | undefined; }
 >nullUnion : { b: number; } | null
 >nullUnion : { b: number; } | null
 
 var o6 = { ...nullAndUndefinedUnion, ...nullAndUndefinedUnion };
->o6 : {} | {} | {} | {}
->{ ...nullAndUndefinedUnion, ...nullAndUndefinedUnion } : {} | {} | {} | {}
+>o6 : {}
+>{ ...nullAndUndefinedUnion, ...nullAndUndefinedUnion } : {}
 >nullAndUndefinedUnion : null | undefined
 >nullAndUndefinedUnion : null | undefined
 
 var o7 = { ...nullAndUndefinedUnion };
->o7 : {} | {}
->{ ...nullAndUndefinedUnion } : {} | {}
+>o7 : {}
+>{ ...nullAndUndefinedUnion } : {}
 >nullAndUndefinedUnion : null | undefined
 

tests/baselines/reference/spreadUnion3.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/conformance/types/spread/spreadUnion3.ts(2,5): error TS2322: Type '{ y: number; } | { y: string; }' is not assignable to type '{ y: string; }'.
-  Type '{ y: number; }' is not assignable to type '{ y: string; }'.
-    Types of property 'y' are incompatible.
+tests/cases/conformance/types/spread/spreadUnion3.ts(2,5): error TS2322: Type '{ y: string | number; }' is not assignable to type '{ y: string; }'.
+  Types of property 'y' are incompatible.
+    Type 'string | number' is not assignable to type 'string'.
       Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/spread/spreadUnion3.ts(9,23): error TS2339: Property 'a' does not exist on type '{} | {} | { a: number; }'.
   Property 'a' does not exist on type '{}'.
@@ -10,9 +10,9 @@ tests/cases/conformance/types/spread/spreadUnion3.ts(9,23): error TS2339: Proper
     function f(x: { y: string } | undefined): { y: string } {
         return { y: 123, ...x } // y: string | number
         ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2322: Type '{ y: number; } | { y: string; }' is not assignable to type '{ y: string; }'.
-!!! error TS2322:   Type '{ y: number; }' is not assignable to type '{ y: string; }'.
-!!! error TS2322:     Types of property 'y' are incompatible.
+!!! error TS2322: Type '{ y: string | number; }' is not assignable to type '{ y: string; }'.
+!!! error TS2322:   Types of property 'y' are incompatible.
+!!! error TS2322:     Type 'string | number' is not assignable to type 'string'.
 !!! error TS2322:       Type 'number' is not assignable to type 'string'.
     }
     f(undefined)

tests/cases/conformance/types/spread/spreadUnion2.ts

@@ -4,20 +4,20 @@ declare const undefinedUnion: { a: number } | undefined;
 declare const nullUnion: { b: number } | null;
 declare const nullAndUndefinedUnion: null | undefined;
 
-var o1: {} | { a: number };
+var o1: { a?: number | undefined };
 var o1 = { ...undefinedUnion };
 
-var o2: {} | { b: number };
+var o2: { b?: number | undefined };
 var o2 = { ...nullUnion };
 
-var o3: {} | { b: number } | { a: number } | { a: number, b: number };
+var o3: { a?: number | undefined, b?: number | undefined };
 var o3 = { ...undefinedUnion, ...nullUnion };
 var o3 = { ...nullUnion, ...undefinedUnion };
 
-var o4: {} | { a: number };
+var o4: { a?: number | undefined };
 var o4 = { ...undefinedUnion, ...undefinedUnion };
 
-var o5: {} | { b: number };
+var o5: { b?: number | undefined };
 var o5 = { ...nullUnion, ...nullUnion };
 
 var o6 = { ...nullAndUndefinedUnion, ...nullAndUndefinedUnion };