Move class property transformation into ESNext transformer

Signed-off-by: Joseph Watts <[email protected]>

Author: Joseph Watts

src/compiler/binder.ts

@@ -3189,8 +3189,7 @@ namespace ts {
             // A ClassDeclaration is ES6 syntax.
             transformFlags = subtreeFlags | TransformFlags.AssertES2015;
 
-            // A class with a parameter property assignment, property initializer, computed property name, or decorator is
-            // TypeScript syntax.
+            // A class with a parameter property assignment or decorator is TypeScript syntax.
             // An exported declaration may be TypeScript syntax, but is handled by the visitor
             // for a namespace declaration.
             if ((subtreeFlags & TransformFlags.ContainsTypeScriptClassSyntax)
@@ -3213,8 +3212,7 @@ namespace ts {
         // A ClassExpression is ES6 syntax.
         let transformFlags = subtreeFlags | TransformFlags.AssertES2015;
 
-        // A class with a parameter property assignment, property initializer, or decorator is
-        // TypeScript syntax.
+        // A class with a parameter property assignment or decorator is TypeScript syntax.
         if (subtreeFlags & TransformFlags.ContainsTypeScriptClassSyntax
             || node.typeParameters) {
             transformFlags |= TransformFlags.AssertTypeScript;
@@ -3310,7 +3308,6 @@ namespace ts {
             || hasModifier(node, ModifierFlags.TypeScriptModifier)
             || node.typeParameters
             || node.type
-            || (node.name && isComputedPropertyName(node.name)) // While computed method names aren't typescript, the TS transform must visit them to emit property declarations correctly
             || !node.body) {
             transformFlags |= TransformFlags.AssertTypeScript;
         }
@@ -3341,7 +3338,6 @@ namespace ts {
         if (node.decorators
             || hasModifier(node, ModifierFlags.TypeScriptModifier)
             || node.type
-            || (node.name && isComputedPropertyName(node.name)) // While computed accessor names aren't typescript, the TS transform must visit them to emit property declarations correctly
             || !node.body) {
             transformFlags |= TransformFlags.AssertTypeScript;
         }
@@ -3356,12 +3352,16 @@ namespace ts {
     }
 
     function computePropertyDeclaration(node: PropertyDeclaration, subtreeFlags: TransformFlags) {
-        // A PropertyDeclaration is TypeScript syntax.
-        let transformFlags = subtreeFlags | TransformFlags.AssertTypeScript;
+        // A PropertyDeclaration is ESnext syntax.
+        let transformFlags = subtreeFlags | TransformFlags.AssertESNext;
 
-        // If the PropertyDeclaration has an initializer or a computed name, we need to inform its ancestor
-        // so that it handle the transformation.
-        if (node.initializer || isComputedPropertyName(node.name)) {
+        // Decorators, TypeScript-specific modifiers, and type annotations are TypeScript syntax.
+        if (some(node.decorators) || hasModifier(node, ModifierFlags.TypeScriptModifier) || node.type) {
+            transformFlags |= TransformFlags.AssertTypeScript;
+        }
+
+        // Hoisted variables related to class properties should live within the TypeScript class wrapper.
+        if (isComputedPropertyName(node.name) || (hasStaticModifier(node) && node.initializer)) {
             transformFlags |= TransformFlags.ContainsTypeScriptClassSyntax;
         }
 
@@ -3762,6 +3762,8 @@ namespace ts {
                 break;
 
             case SyntaxKind.ComputedPropertyName:
+                // Computed property names are transformed by the ESNext transformer.
+                transformFlags |= TransformFlags.AssertESNext;
                 // Even though computed property names are ES6, we don't treat them as such.
                 // This is so that they can flow through PropertyName transforms unaffected.
                 // Instead, we mark the container as ES6, so that it can properly handle the transform.