Consider class field properties to redeclare parent definitions

Author: Josh Goldberg

src/compiler/checker.ts

@@ -26861,7 +26861,7 @@ namespace ts {
             if (isInPropertyInitializer(node)
                 && !(isAccessExpression(node) && isAccessExpression(node.expression))
                 && !isBlockScopedNameDeclaredBeforeUse(valueDeclaration, right)
-                && !isPropertyDeclaredInAncestorClass(prop)) {
+                && (compilerOptions.useDefineForClassFields || !isPropertyDeclaredInAncestorClass(prop))) {
                 diagnosticMessage = error(right, Diagnostics.Property_0_is_used_before_its_initialization, declarationName);
             }
             else if (valueDeclaration.kind === SyntaxKind.ClassDeclaration &&

tests/baselines/reference/redeclaredProperty.errors.txt

@@ -0,0 +1,21 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/redeclaredProperty.ts(7,12): error TS2729: Property 'b' is used before its initialization.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/redeclaredProperty.ts (1 errors) ====
+    class Base {
+      b = 1;
+    }
+    
+    class Derived extends Base {
+      b;
+      d = this.b;
+               ~
+!!! error TS2729: Property 'b' is used before its initialization.
+!!! related TS2728 tests/cases/conformance/classes/propertyMemberDeclarations/redeclaredProperty.ts:6:3: 'b' is declared here.
+    
+      constructor() {
+        super();
+        this.b = 2;
+      }
+    }
+    

tests/baselines/reference/redeclaredProperty.js

@@ -0,0 +1,28 @@
+//// [redeclaredProperty.ts]
+class Base {
+  b = 1;
+}
+
+class Derived extends Base {
+  b;
+  d = this.b;
+
+  constructor() {
+    super();
+    this.b = 2;
+  }
+}
+
+
+//// [redeclaredProperty.js]
+class Base {
+    b = 1;
+}
+class Derived extends Base {
+    b;
+    d = this.b;
+    constructor() {
+        super();
+        this.b = 2;
+    }
+}

tests/baselines/reference/redefinedPararameterProperty.errors.txt

@@ -0,0 +1,19 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/redefinedPararameterProperty.ts(6,14): error TS2729: Property 'a' is used before its initialization.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/redefinedPararameterProperty.ts (1 errors) ====
+    class Base {
+        a = 1;
+      }
+      
+      class Derived extends Base {
+        b = this.a /*undefined*/;
+                 ~
+!!! error TS2729: Property 'a' is used before its initialization.
+!!! related TS2728 tests/cases/conformance/classes/propertyMemberDeclarations/redefinedPararameterProperty.ts:8:17: 'a' is declared here.
+      
+        constructor(public a: number) {
+            super();
+        }
+      }
+      

tests/baselines/reference/redefinedPararameterProperty.js

@@ -0,0 +1,26 @@
+//// [redefinedPararameterProperty.ts]
+class Base {
+    a = 1;
+  }
+  
+  class Derived extends Base {
+    b = this.a /*undefined*/;
+  
+    constructor(public a: number) {
+        super();
+    }
+  }
+  
+
+//// [redefinedPararameterProperty.js]
+class Base {
+    a = 1;
+}
+class Derived extends Base {
+    a;
+    b = this.a /*undefined*/;
+    constructor(a) {
+        super();
+        this.a = a;
+    }
+}

tests/baselines/reference/redefinedPararameterProperty.symbols

@@ -0,0 +1,3 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/redefinedPararameterProperty.ts ===
+
+No type information for this code.

tests/baselines/reference/redefinedPararameterProperty.types

@@ -0,0 +1,3 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/redefinedPararameterProperty.ts ===
+
+No type information for this code.

tests/cases/conformance/classes/propertyMemberDeclarations/redeclaredProperty.ts

@@ -0,0 +1,17 @@
+// @noTypesAndSymbols: true
+// @strictNullChecks: true
+// @target: esnext
+// @useDefineForClassFields: true
+class Base {
+  b = 1;
+}
+
+class Derived extends Base {
+  b;
+  d = this.b;
+
+  constructor() {
+    super();
+    this.b = 2;
+  }
+}

tests/cases/conformance/classes/propertyMemberDeclarations/redefinedPararameterProperty.ts

@@ -0,0 +1,16 @@
+// @noTypesAndSymbols: true
+// @strictNullChecks: true
+// @target: esnext
+// @useDefineForClassFields: true
+class Base {
+    a = 1;
+  }
+  
+  class Derived extends Base {
+    b = this.a /*undefined*/;
+  
+    constructor(public a: number) {
+        super();
+    }
+  }
+