Always error when property overrides accessor or vice versa

Previously this was only an error when useDefineForClassFields: true,
but now it's an error for all code. This is a rare mistake to make, and
usually only occurs in code written before `readonly` was available.

Codefix to come in subsequent commits.

Author: sandersn

src/compiler/checker.ts

@@ -33373,8 +33373,7 @@ namespace ts {
                     const derivedPropertyFlags = derived.flags & SymbolFlags.PropertyOrAccessor;
                     if (basePropertyFlags && derivedPropertyFlags) {
                         // property/accessor is overridden with property/accessor
-                        if (!compilerOptions.useDefineForClassFields
-                            || baseDeclarationFlags & ModifierFlags.Abstract && !(base.valueDeclaration && isPropertyDeclaration(base.valueDeclaration) && base.valueDeclaration.initializer)
+                        if (baseDeclarationFlags & ModifierFlags.Abstract && !(base.valueDeclaration && isPropertyDeclaration(base.valueDeclaration) && base.valueDeclaration.initializer)
                             || base.valueDeclaration && base.valueDeclaration.parent.kind === SyntaxKind.InterfaceDeclaration
                             || derived.valueDeclaration && isBinaryExpression(derived.valueDeclaration)) {
                             // when the base property is abstract or from an interface, base/derived flags don't need to match
@@ -33390,7 +33389,7 @@ namespace ts {
                                 Diagnostics._0_is_defined_as_a_property_in_class_1_but_is_overridden_here_in_2_as_an_accessor;
                             error(getNameOfDeclaration(derived.valueDeclaration) || derived.valueDeclaration, errorMessage, symbolToString(base), typeToString(baseType), typeToString(type));
                         }
-                        else {
+                        else if (compilerOptions.useDefineForClassFields) {
                             const uninitialized = find(derived.declarations, d => d.kind === SyntaxKind.PropertyDeclaration && !(d as PropertyDeclaration).initializer);
                             if (uninitialized
                                 && !(derived.flags & SymbolFlags.Transient)

tests/baselines/reference/accessorsOverrideProperty6.errors.txt

@@ -0,0 +1,24 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty6.ts(5,9): error TS2611: 'p' is defined as a property in class 'A', but is overridden here in 'B' as an accessor.
+tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty6.ts(12,9): error TS2611: 'p' is defined as a property in class 'C', but is overridden here in 'D' as an accessor.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty6.ts (2 errors) ====
+    class A {
+        p = 'yep'
+    }
+    class B extends A {
+        get p() { return 'oh no' } // error
+            ~
+!!! error TS2611: 'p' is defined as a property in class 'A', but is overridden here in 'B' as an accessor.
+    }
+    class C {
+       p = 101
+    }
+    class D extends C {
+         _secret = 11
+        get p() { return this._secret } // error
+            ~
+!!! error TS2611: 'p' is defined as a property in class 'C', but is overridden here in 'D' as an accessor.
+        set p(value) { this._secret = value } // error
+    }
+    

tests/baselines/reference/inheritanceMemberAccessorOverridingProperty.errors.txt

@@ -1,8 +1,9 @@
 tests/cases/compiler/inheritanceMemberAccessorOverridingProperty.ts(6,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
+tests/cases/compiler/inheritanceMemberAccessorOverridingProperty.ts(6,9): error TS2611: 'x' is defined as a property in class 'a', but is overridden here in 'b' as an accessor.
 tests/cases/compiler/inheritanceMemberAccessorOverridingProperty.ts(9,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 
 
-==== tests/cases/compiler/inheritanceMemberAccessorOverridingProperty.ts (2 errors) ====
+==== tests/cases/compiler/inheritanceMemberAccessorOverridingProperty.ts (3 errors) ====
     class a {
         x: string;
     }
@@ -11,6 +12,8 @@ tests/cases/compiler/inheritanceMemberAccessorOverridingProperty.ts(9,9): error
         get x() {
             ~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
+            ~
+!!! error TS2611: 'x' is defined as a property in class 'a', but is overridden here in 'b' as an accessor.
             return "20";
         }
         set x(aValue: string) {

tests/baselines/reference/inheritanceMemberPropertyOverridingAccessor.errors.txt

@@ -1,8 +1,9 @@
 tests/cases/compiler/inheritanceMemberPropertyOverridingAccessor.ts(3,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
 tests/cases/compiler/inheritanceMemberPropertyOverridingAccessor.ts(6,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
+tests/cases/compiler/inheritanceMemberPropertyOverridingAccessor.ts(12,5): error TS2610: 'x' is defined as an accessor in class 'a', but is overridden here in 'b' as an instance property.
 
 
-==== tests/cases/compiler/inheritanceMemberPropertyOverridingAccessor.ts (2 errors) ====
+==== tests/cases/compiler/inheritanceMemberPropertyOverridingAccessor.ts (3 errors) ====
     class a {
         private __x: () => string;
         get x() {
@@ -19,4 +20,6 @@ tests/cases/compiler/inheritanceMemberPropertyOverridingAccessor.ts(6,9): error
 
     class b extends a {
         x: () => string;
+        ~
+!!! error TS2610: 'x' is defined as an accessor in class 'a', but is overridden here in 'b' as an instance property.
     }

tests/baselines/reference/tscWatch/programUpdates/updates-diagnostics-and-emit-when-useDefineForClassFields-changes.js

@@ -37,7 +37,13 @@ Output::
 [12:00:13 AM] Starting compilation in watch mode...
 
 
-[12:00:16 AM] Found 0 errors. Watching for file changes.
+a.ts:2:21 - error TS2610: 'prop' is defined as an accessor in class 'C', but is overridden here in 'D' as an instance property.
+
+2 class D extends C { prop = 1; }
+                      ~~~~
+
+
+[12:00:16 AM] Found 1 error. Watching for file changes.