Filter primitives from union when checking for mismatched excess props if nonprimitive type is present

src/compiler/checker.ts

@@ -12600,8 +12600,8 @@ namespace ts {
                         result = typeRelatedToSomeType(getRegularTypeOfObjectLiteral(source), <UnionType>target, reportErrors && !(source.flags & TypeFlags.Primitive) && !(target.flags & TypeFlags.Primitive));
                         if (result && isPerformingExcessPropertyChecks) {
                             // Validate against excess props using the original `source`
-                            const discriminantType = target.flags & TypeFlags.Union ? findMatchingDiscriminantType(source, target as UnionType) : undefined;
-                            if (!propertiesRelatedTo(source, discriminantType || target, reportErrors, /*excludedProperties*/ undefined)) {
+                            const discriminantType = findMatchingDiscriminantType(source, target as UnionType) || filterPrimitivesIfContainsNonPrimitive(target as UnionType);
+                            if (!propertiesRelatedTo(source, discriminantType, reportErrors, /*excludedProperties*/ undefined)) {
                                 return Ternary.False;
                             }
                         }
@@ -12872,6 +12872,16 @@ namespace ts {
                 return bestMatch;
             }
 
+            function filterPrimitivesIfContainsNonPrimitive(type: UnionType) {
+                if (maybeTypeOfKind(type, TypeFlags.NonPrimitive)) {
+                    const result = filterType(type, t => !(t.flags & TypeFlags.Primitive));
+                    if (!(result.flags & TypeFlags.Never)) {
+                        return result;
+                    }
+                }
+                return type;
+            }
+
             // Keep this up-to-date with the same logic within `getApparentTypeOfContextualType`, since they should behave similarly
             function findMatchingDiscriminantType(source: Type, target: Type) {
                 if (target.flags & TypeFlags.Union && source.flags & (TypeFlags.Intersection | TypeFlags.Object)) {

tests/baselines/reference/discriminateObjectTypesOnly.errors.txt

@@ -0,0 +1,17 @@
+tests/cases/compiler/discriminateObjectTypesOnly.ts(9,7): error TS2741: Property 'toFixed' is missing in type '{ toString: undefined; }' but required in type '{ toFixed: null; toString: undefined; }'.
+
+
+==== tests/cases/compiler/discriminateObjectTypesOnly.ts (1 errors) ====
+    type Thing = number | object;
+    const k: Thing = { toFixed: null }; // OK, satisfies object
+
+    type Thing2 = number | { toFixed: null } | object;
+    const q: Thing2 = { toFixed: null };
+    const h: Thing2 = { toString: null }; // OK, satisfies object
+
+    type Thing3 = number | { toFixed: null, toString: undefined } | object;
+    const l: Thing3 = { toString: undefined }; // error, toFixed isn't null
+          ~
+!!! error TS2741: Property 'toFixed' is missing in type '{ toString: undefined; }' but required in type '{ toFixed: null; toString: undefined; }'.
+!!! related TS2728 tests/cases/compiler/discriminateObjectTypesOnly.ts:8:26: 'toFixed' is declared here.
+

tests/baselines/reference/discriminateObjectTypesOnly.js

@@ -0,0 +1,18 @@
+//// [discriminateObjectTypesOnly.ts]
+type Thing = number | object;
+const k: Thing = { toFixed: null }; // OK, satisfies object
+
+type Thing2 = number | { toFixed: null } | object;
+const q: Thing2 = { toFixed: null };
+const h: Thing2 = { toString: null }; // OK, satisfies object
+
+type Thing3 = number | { toFixed: null, toString: undefined } | object;
+const l: Thing3 = { toString: undefined }; // error, toFixed isn't null
+
+
+//// [discriminateObjectTypesOnly.js]
+"use strict";
+var k = { toFixed: null }; // OK, satisfies object
+var q = { toFixed: null };
+var h = { toString: null }; // OK, satisfies object
+var l = { toString: undefined }; // error, toFixed isn't null

tests/baselines/reference/discriminateObjectTypesOnly.symbols

@@ -0,0 +1,34 @@
+=== tests/cases/compiler/discriminateObjectTypesOnly.ts ===
+type Thing = number | object;
+>Thing : Symbol(Thing, Decl(discriminateObjectTypesOnly.ts, 0, 0))
+
+const k: Thing = { toFixed: null }; // OK, satisfies object
+>k : Symbol(k, Decl(discriminateObjectTypesOnly.ts, 1, 5))
+>Thing : Symbol(Thing, Decl(discriminateObjectTypesOnly.ts, 0, 0))
+>toFixed : Symbol(toFixed, Decl(discriminateObjectTypesOnly.ts, 1, 18))
+
+type Thing2 = number | { toFixed: null } | object;
+>Thing2 : Symbol(Thing2, Decl(discriminateObjectTypesOnly.ts, 1, 35))
+>toFixed : Symbol(toFixed, Decl(discriminateObjectTypesOnly.ts, 3, 24))
+
+const q: Thing2 = { toFixed: null };
+>q : Symbol(q, Decl(discriminateObjectTypesOnly.ts, 4, 5))
+>Thing2 : Symbol(Thing2, Decl(discriminateObjectTypesOnly.ts, 1, 35))
+>toFixed : Symbol(toFixed, Decl(discriminateObjectTypesOnly.ts, 4, 19))
+
+const h: Thing2 = { toString: null }; // OK, satisfies object
+>h : Symbol(h, Decl(discriminateObjectTypesOnly.ts, 5, 5))
+>Thing2 : Symbol(Thing2, Decl(discriminateObjectTypesOnly.ts, 1, 35))
+>toString : Symbol(toString, Decl(discriminateObjectTypesOnly.ts, 5, 19))
+
+type Thing3 = number | { toFixed: null, toString: undefined } | object;
+>Thing3 : Symbol(Thing3, Decl(discriminateObjectTypesOnly.ts, 5, 37))
+>toFixed : Symbol(toFixed, Decl(discriminateObjectTypesOnly.ts, 7, 24))
+>toString : Symbol(toString, Decl(discriminateObjectTypesOnly.ts, 7, 39))
+
+const l: Thing3 = { toString: undefined }; // error, toFixed isn't null
+>l : Symbol(l, Decl(discriminateObjectTypesOnly.ts, 8, 5))
+>Thing3 : Symbol(Thing3, Decl(discriminateObjectTypesOnly.ts, 5, 37))
+>toString : Symbol(toString, Decl(discriminateObjectTypesOnly.ts, 8, 19))
+>undefined : Symbol(undefined)
+

tests/baselines/reference/discriminateObjectTypesOnly.types

@@ -0,0 +1,39 @@
+=== tests/cases/compiler/discriminateObjectTypesOnly.ts ===
+type Thing = number | object;
+>Thing : Thing
+
+const k: Thing = { toFixed: null }; // OK, satisfies object
+>k : Thing
+>{ toFixed: null } : { toFixed: null; }
+>toFixed : null
+>null : null
+
+type Thing2 = number | { toFixed: null } | object;
+>Thing2 : Thing2
+>toFixed : null
+>null : null
+
+const q: Thing2 = { toFixed: null };
+>q : Thing2
+>{ toFixed: null } : { toFixed: null; }
+>toFixed : null
+>null : null
+
+const h: Thing2 = { toString: null }; // OK, satisfies object
+>h : Thing2
+>{ toString: null } : { toString: null; }
+>toString : null
+>null : null
+
+type Thing3 = number | { toFixed: null, toString: undefined } | object;
+>Thing3 : Thing3
+>toFixed : null
+>null : null
+>toString : undefined
+
+const l: Thing3 = { toString: undefined }; // error, toFixed isn't null
+>l : Thing3
+>{ toString: undefined } : { toString: undefined; }
+>toString : undefined
+>undefined : undefined
+

tests/cases/compiler/discriminateObjectTypesOnly.ts

@@ -0,0 +1,10 @@
+// @strict: true
+type Thing = number | object;
+const k: Thing = { toFixed: null }; // OK, satisfies object
+
+type Thing2 = number | { toFixed: null } | object;
+const q: Thing2 = { toFixed: null };
+const h: Thing2 = { toString: null }; // OK, satisfies object
+
+type Thing3 = number | { toFixed: null, toString: undefined } | object;
+const l: Thing3 = { toString: undefined }; // error, toFixed isn't null