Move class property transformation into new transformer. (#30467)

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

Author: joeywatts

src/compiler/binder.ts

@@ -3229,8 +3229,7 @@ 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)
@@ -3247,8 +3246,7 @@ 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;
@@ -3338,7 +3336,6 @@ 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;
         }
@@ -3369,7 +3366,6 @@ 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;
         }
@@ -3384,12 +3380,15 @@ namespace ts {
     }
 
     function computePropertyDeclaration(node: PropertyDeclaration, subtreeFlags: TransformFlags) {
-        // A PropertyDeclaration is TypeScript syntax.
-        let transformFlags = subtreeFlags | TransformFlags.AssertTypeScript;
+        let transformFlags = subtreeFlags | TransformFlags.ContainsClassFields;
+
+        // Decorators, TypeScript-specific modifiers, and type annotations are TypeScript syntax.
+        if (some(node.decorators) || hasModifier(node, ModifierFlags.TypeScriptModifier) || node.type) {
+            transformFlags |= TransformFlags.AssertTypeScript;
+        }
 
-        // 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)) {
+        // Hoisted variables related to class properties should live within the TypeScript class wrapper.
+        if (isComputedPropertyName(node.name) || (hasStaticModifier(node) && node.initializer)) {
             transformFlags |= TransformFlags.ContainsTypeScriptClassSyntax;
         }
 

src/compiler/transformer.ts

@@ -44,6 +44,7 @@ namespace ts {
         addRange(transformers, customTransformers && map(customTransformers.before, wrapScriptTransformerFactory));
 
         transformers.push(transformTypeScript);
+        transformers.push(transformClassFields);
 
         if (jsx === JsxEmit.React) {
             transformers.push(transformJsx);

src/compiler/transformers/classFields.ts

@@ -240,6 +240,47 @@ namespace ts {
             isIdentifier(expression);
     }
 
+    /**
+     * A simple inlinable expression is an expression which can be copied into multiple locations
+     * without risk of repeating any sideeffects and whose value could not possibly change between
+     * any such locations
+     */
+    export function isSimpleInlineableExpression(expression: Expression) {
+        return !isIdentifier(expression) && isSimpleCopiableExpression(expression) ||
+            isWellKnownSymbolSyntactically(expression);
+    }
+
+    /**
+     * Adds super call and preceding prologue directives into the list of statements.
+     *
+     * @param ctor The constructor node.
+     * @param result The list of statements.
+     * @param visitor The visitor to apply to each node added to the result array.
+     * @returns index of the statement that follows super call
+     */
+    export function addPrologueDirectivesAndInitialSuperCall(ctor: ConstructorDeclaration, result: Statement[], visitor: Visitor): number {
+        if (ctor.body) {
+            const statements = ctor.body.statements;
+            // add prologue directives to the list (if any)
+            const index = addPrologue(result, statements, /*ensureUseStrict*/ false, visitor);
+            if (index === statements.length) {
+                // list contains nothing but prologue directives (or empty) - exit
+                return index;
+            }
+
+            const statement = statements[index];
+            if (statement.kind === SyntaxKind.ExpressionStatement && isSuperCall((<ExpressionStatement>statement).expression)) {
+                result.push(visitNode(statement, visitor, isStatement));
+                return index + 1;
+            }
+
+            return index;
+        }
+
+        return 0;
+    }
+
+
     /**
      * @param input Template string input strings
      * @param args Names which need to be made file-level unique
@@ -255,4 +296,43 @@ namespace ts {
             return result;
         };
     }
+
+    /**
+     * Gets all property declarations with initializers on either the static or instance side of a class.
+     *
+     * @param node The class node.
+     * @param isStatic A value indicating whether to get properties from the static or instance side of the class.
+     */
+    export function getInitializedProperties(node: ClassExpression | ClassDeclaration, isStatic: boolean): ReadonlyArray<PropertyDeclaration> {
+        return filter(node.members, isStatic ? isStaticInitializedProperty : isInstanceInitializedProperty);
+    }
+
+    /**
+     * Gets a value indicating whether a class element is a static property declaration with an initializer.
+     *
+     * @param member The class element node.
+     */
+    export function isStaticInitializedProperty(member: ClassElement): member is PropertyDeclaration & { initializer: Expression; } {
+        return isInitializedProperty(member) && hasStaticModifier(member);
+    }
+
+    /**
+     * Gets a value indicating whether a class element is an instance property declaration with an initializer.
+     *
+     * @param member The class element node.
+     */
+    export function isInstanceInitializedProperty(member: ClassElement): member is PropertyDeclaration & { initializer: Expression; } {
+        return isInitializedProperty(member) && !hasStaticModifier(member);
+    }
+
+    /**
+     * Gets a value indicating whether a class element is either a static or an instance property declaration with an initializer.
+     *
+     * @param member The class element node.
+     * @param isStatic A value indicating whether the member should be a static or instance member.
+     */
+    export function isInitializedProperty(member: ClassElement): member is PropertyDeclaration & { initializer: Expression; } {
+        return member.kind === SyntaxKind.PropertyDeclaration
+            && (<PropertyDeclaration>member).initializer !== undefined;
+    }
 }

src/compiler/transformers/ts.ts

@@ -30,6 +30,7 @@
         "transformers/utilities.ts",
         "transformers/destructuring.ts",
         "transformers/ts.ts",
+        "transformers/classFields.ts",
         "transformers/es2017.ts",
         "transformers/es2018.ts",
         "transformers/es2019.ts",

src/compiler/transformers/utilities.ts

@@ -5197,6 +5197,7 @@ namespace ts {
         ContainsYield = 1 << 17,
         ContainsHoistedDeclarationOrCompletion = 1 << 18,
         ContainsDynamicImport = 1 << 19,
+        ContainsClassFields = 1 << 20,
 
         // Please leave this as 1 << 29.
         // It is the maximum bit we can set before we outgrow the size of a v8 small integer (SMI) on an x86 system.

src/compiler/tsconfig.json

@@ -34,8 +34,8 @@ var C = /** @class */ (function () {
     }
     return C;
 }());
-_a = a_1.x;
 exports.C = C;
+_a = a_1.x;
 //// [c.js]
 "use strict";
 var __extends = (this && this.__extends) || (function () {
@@ -64,8 +64,8 @@ var D = /** @class */ (function (_super) {
     }
     return D;
 }(b_1.C));
-_a = a_1.x;
 exports.D = D;
+_a = a_1.x;
 
 
 //// [a.d.ts]