Fix isPropertyDeclaredInAncestorClass function (#2376)

Author: ahejlsberg

internal/checker/checker.go

@@ -11368,21 +11368,13 @@ func (c *Checker) isOptionalPropertyDeclaration(node *ast.Node) bool {
 }
 
 func (c *Checker) isPropertyDeclaredInAncestorClass(prop *ast.Symbol) bool {
-	if prop.Parent.Flags&ast.SymbolFlagsClass == 0 {
-		return false
-	}
-	classType := c.getDeclaredTypeOfSymbol(prop.Parent)
-	for {
-		baseTypes := c.getBaseTypes(classType)
-		if len(baseTypes) == 0 {
-			return false
-		}
-		classType = baseTypes[0]
-		superProperty := c.getPropertyOfType(classType, prop.Name)
-		if superProperty != nil && superProperty.ValueDeclaration != nil {
-			return true
+	if prop.Parent.Flags&ast.SymbolFlagsClass != 0 {
+		if baseTypes := c.getBaseTypes(c.getDeclaredTypeOfSymbol(prop.Parent)); len(baseTypes) != 0 {
+			superProperty := c.getPropertyOfType(baseTypes[0], prop.Name)
+			return superProperty != nil && superProperty.ValueDeclaration != nil
 		}
 	}
+	return false
 }
 
 /**

testdata/baselines/reference/compiler/checkInheritedProperty.errors.txt

@@ -0,0 +1,17 @@
+checkInheritedProperty.ts(7,14): error TS2729: Property 'b' is used before its initialization.
+
+
+==== checkInheritedProperty.ts (1 errors) ====
+    class Base {
+    }
+    
+    declare const BaseFactory: new() => Base & { c: string }
+    
+    class Derived extends BaseFactory {
+        a = this.b
+                 ~
+!!! error TS2729: Property 'b' is used before its initialization.
+!!! related TS2728 checkInheritedProperty.ts:8:5: 'b' is declared here.
+        b = "abc"
+    }
+    

testdata/baselines/reference/compiler/checkInheritedProperty.symbols

@@ -0,0 +1,26 @@
+//// [tests/cases/compiler/checkInheritedProperty.ts] ////
+
+=== checkInheritedProperty.ts ===
+class Base {
+>Base : Symbol(Base, Decl(checkInheritedProperty.ts, 0, 0))
+}
+
+declare const BaseFactory: new() => Base & { c: string }
+>BaseFactory : Symbol(BaseFactory, Decl(checkInheritedProperty.ts, 3, 13))
+>Base : Symbol(Base, Decl(checkInheritedProperty.ts, 0, 0))
+>c : Symbol(c, Decl(checkInheritedProperty.ts, 3, 44))
+
+class Derived extends BaseFactory {
+>Derived : Symbol(Derived, Decl(checkInheritedProperty.ts, 3, 56))
+>BaseFactory : Symbol(BaseFactory, Decl(checkInheritedProperty.ts, 3, 13))
+
+    a = this.b
+>a : Symbol(Derived.a, Decl(checkInheritedProperty.ts, 5, 35))
+>this.b : Symbol(Derived.b, Decl(checkInheritedProperty.ts, 6, 14))
+>this : Symbol(Derived, Decl(checkInheritedProperty.ts, 3, 56))
+>b : Symbol(Derived.b, Decl(checkInheritedProperty.ts, 6, 14))
+
+    b = "abc"
+>b : Symbol(Derived.b, Decl(checkInheritedProperty.ts, 6, 14))
+}
+

testdata/baselines/reference/compiler/checkInheritedProperty.types

@@ -0,0 +1,26 @@
+//// [tests/cases/compiler/checkInheritedProperty.ts] ////
+
+=== checkInheritedProperty.ts ===
+class Base {
+>Base : Base
+}
+
+declare const BaseFactory: new() => Base & { c: string }
+>BaseFactory : new () => Base & { c: string; }
+>c : string
+
+class Derived extends BaseFactory {
+>Derived : Derived
+>BaseFactory : Base & { c: string; }
+
+    a = this.b
+>a : string
+>this.b : string
+>this : this
+>b : string
+
+    b = "abc"
+>b : string
+>"abc" : "abc"
+}
+

testdata/tests/cases/compiler/checkInheritedProperty.ts

@@ -0,0 +1,12 @@
+// @strict: true
+// @noEmit: true
+
+class Base {
+}
+
+declare const BaseFactory: new() => Base & { c: string }
+
+class Derived extends BaseFactory {
+    a = this.b
+    b = "abc"
+}