🤖 Pick PR #58083 (Don't propagate partial union/inter...) into release-5.4 (#58136)

Co-authored-by: Anders Hejlsberg <andersh@microsoft.com>

src/compiler/checker.ts

@@ -14788,8 +14788,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     // these partial properties when identifying discriminant properties, but otherwise they are filtered out
     // and do not appear to be present in the union type.
     function getUnionOrIntersectionProperty(type: UnionOrIntersectionType, name: __String, skipObjectFunctionPropertyAugment?: boolean): Symbol | undefined {
-        let property = type.propertyCacheWithoutObjectFunctionPropertyAugment?.get(name) ||
-                !skipObjectFunctionPropertyAugment ? type.propertyCache?.get(name) : undefined;
+        let property = skipObjectFunctionPropertyAugment ?
+            type.propertyCacheWithoutObjectFunctionPropertyAugment?.get(name) :
+            type.propertyCache?.get(name);
         if (!property) {
             property = createUnionOrIntersectionProperty(type, name, skipObjectFunctionPropertyAugment);
             if (property) {
@@ -14797,7 +14798,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     type.propertyCacheWithoutObjectFunctionPropertyAugment ||= createSymbolTable() :
                     type.propertyCache ||= createSymbolTable();
                 properties.set(name, property);
-                if (skipObjectFunctionPropertyAugment && !type.propertyCache?.get(name)) {
+                // Propagate an entry from the non-augmented cache to the augmented cache unless the property is partial.
+                if (skipObjectFunctionPropertyAugment && !(getCheckFlags(property) & CheckFlags.Partial) && !type.propertyCache?.get(name)) {
                     const properties = type.propertyCache ||= createSymbolTable();
                     properties.set(name, property);
                 }

tests/cases/fourslash/partialUnionPropertyCacheInconsistentErrors.ts

@@ -0,0 +1,45 @@
+/// <reference path="fourslash.ts" />
+
+// @strict: true
+// @lib: esnext
+
+//// interface ComponentOptions<Props> {
+////   setup?: (props: Props) => void;
+////   name?: string;
+//// }
+//// 
+//// interface FunctionalComponent<P> {
+////   (props: P): void;
+//// }
+//// 
+//// type ConcreteComponent<Props> =
+////   | ComponentOptions<Props>
+////   | FunctionalComponent<Props>;
+//// 
+//// type Component<Props = {}> = ConcreteComponent<Props>;
+//// 
+//// type WithInstallPlugin = { _prefix?: string };
+//// 
+//// 
+//// /**/
+//// export function withInstall<C extends Component, T extends WithInstallPlugin>(
+////   component: C | C[],
+////   target?: T,
+//// ): string {
+////   const componentWithInstall = (target ?? component) as T;
+////   const components = Array.isArray(component) ? component : [component];
+//// 
+////   const { name } = components[0];
+////   if (name) {
+////     return name;
+////   }
+//// 
+////   return "";
+//// }
+
+verify.noErrors();
+
+goTo.marker();
+edit.insert("type C = Component['name']");
+
+verify.noErrors();