Cherry-pick PR microsoft#34987 into release-3.7

Component commits:
5810765 Emit defineProperty calls before param prop assignments
Note that I restricted this to --useDefineForClassFields is true.
Nothing changes when it's off. I think this is the correct fix for a
patch release.

However, in principal there's nothing wrong with moving parameter
property initialisation after property declaration initialisation. It
would be Extremely Bad and Wrong to rely on this working:

```ts
class C {
  p = this.q // what is q?
  constructor(public q: number) { }
}
```

But today it does, and probably somebody relies on it without knowing.

ec79590 Put parameter property initialiser into defineProperty's value

Author: sandersn

src/compiler/transformers/classFields.ts

@@ -10,9 +10,9 @@ namespace ts {
     /**
      * Transforms ECMAScript Class Syntax.
      * TypeScript parameter property syntax is transformed in the TypeScript transformer.
-     * For now, this transforms public field declarations using TypeScript class semantics
-     * (where the declarations get elided and initializers are transformed as assignments in the constructor).
-     * Eventually, this transform will change to the ECMAScript semantics (with Object.defineProperty).
+     * For now, this transforms public field declarations using TypeScript class semantics,
+     * where declarations are elided and initializers are transformed as assignments in the constructor.
+     * When --useDefineForClassFields is on, this transforms to ECMAScript semantics, with Object.defineProperty.
      */
     export function transformClassFields(context: TransformationContext) {
         const {
@@ -294,7 +294,8 @@ namespace ts {
         }
 
         function transformConstructorBody(node: ClassDeclaration | ClassExpression, constructor: ConstructorDeclaration | undefined, isDerivedClass: boolean) {
-            const properties = getProperties(node, /*requireInitializer*/ !context.getCompilerOptions().useDefineForClassFields, /*isStatic*/ false);
+            const useDefineForClassFields = context.getCompilerOptions().useDefineForClassFields;
+            const properties = getProperties(node, /*requireInitializer*/ !useDefineForClassFields, /*isStatic*/ false);
 
             // Only generate synthetic constructor when there are property initializers to move.
             if (!constructor && !some(properties)) {
@@ -325,7 +326,6 @@ namespace ts {
             if (constructor) {
                 indexOfFirstStatement = addPrologueDirectivesAndInitialSuperCall(constructor, statements, visitor);
             }
-
             // Add the property initializers. Transforms this:
             //
             //  public x = 1;
@@ -336,19 +336,16 @@ namespace ts {
             //      this.x = 1;
             //  }
             //
-            if (constructor && constructor.body) {
-                let parameterPropertyDeclarationCount = 0;
-                for (let i = indexOfFirstStatement; i < constructor.body.statements.length; i++) {
-                    if (isParameterPropertyDeclaration(getOriginalNode(constructor.body.statements[i]), constructor)) {
-                        parameterPropertyDeclarationCount++;
-                    }
-                    else {
-                        break;
-                    }
+            if (constructor?.body) {
+                let afterParameterProperties = findIndex(constructor.body.statements, s => !isParameterPropertyDeclaration(getOriginalNode(s), constructor), indexOfFirstStatement);
+                if (afterParameterProperties === -1) {
+                    afterParameterProperties = constructor.body.statements.length;
                 }
-                if (parameterPropertyDeclarationCount > 0) {
-                    addRange(statements, visitNodes(constructor.body.statements, visitor, isStatement, indexOfFirstStatement, parameterPropertyDeclarationCount));
-                    indexOfFirstStatement += parameterPropertyDeclarationCount;
+                if (afterParameterProperties > indexOfFirstStatement) {
+                    if (!useDefineForClassFields) {
+                        addRange(statements, visitNodes(constructor.body.statements, visitor, isStatement, indexOfFirstStatement, afterParameterProperties - indexOfFirstStatement));
+                    }
+                    indexOfFirstStatement = afterParameterProperties;
                 }
             }
             addPropertyStatements(statements, properties, createThis());
@@ -421,7 +418,9 @@ namespace ts {
                 ? updateComputedPropertyName(property.name, getGeneratedNameForNode(property.name))
                 : property.name;
 
-            const initializer = property.initializer || emitAssignment ? visitNode(property.initializer, visitor, isExpression) : createVoidZero();
+            const initializer = property.initializer || emitAssignment ? visitNode(property.initializer, visitor, isExpression)
+                : hasModifier(getOriginalNode(property), ModifierFlags.ParameterPropertyModifier) && isIdentifier(propertyName) ? propertyName
+                : createVoidZero();
             if (emitAssignment) {
                 const memberAccess = createMemberAccessForPropertyName(receiver, propertyName, /*location*/ propertyName);
                 return createAssignment(memberAccess, initializer);

src/compiler/transformers/ts.ts

@@ -900,13 +900,13 @@ namespace ts {
             if (parametersWithPropertyAssignments) {
                 for (const parameter of parametersWithPropertyAssignments) {
                     if (isIdentifier(parameter.name)) {
-                        members.push(aggregateTransformFlags(createProperty(
+                        members.push(setOriginalNode(aggregateTransformFlags(createProperty(
                             /*decorators*/ undefined,
                             /*modifiers*/ undefined,
                             parameter.name,
                             /*questionOrExclamationToken*/ undefined,
                             /*type*/ undefined,
-                            /*initializer*/ undefined)));
+                            /*initializer*/ undefined)), parameter));
                     }
                 }
             }

tests/baselines/reference/definePropertyES5.js

@@ -1,24 +1,32 @@
 //// [definePropertyES5.ts]
 var x: "p" = "p"
 class A {
-    a = 12
+    a = this.y
     b
     ["computed"] = 13
     ;[x] = 14
     m() { }
+    constructor(public readonly y: number) { }
+    z = this.y
 }
 
 
 //// [definePropertyES5.js]
 var _a;
 var x = "p";
 var A = /** @class */ (function () {
-    function A() {
+    function A(y) {
+        Object.defineProperty(this, "y", {
+            enumerable: true,
+            configurable: true,
+            writable: true,
+            value: y
+        });
         Object.defineProperty(this, "a", {
             enumerable: true,
             configurable: true,
             writable: true,
-            value: 12
+            value: this.y
         });
         Object.defineProperty(this, "b", {
             enumerable: true,
@@ -38,6 +46,12 @@ var A = /** @class */ (function () {
             writable: true,
             value: 14
         });
+        Object.defineProperty(this, "z", {
+            enumerable: true,
+            configurable: true,
+            writable: true,
+            value: this.y
+        });
     }
     Object.defineProperty(A.prototype, "m", {
         enumerable: false,

tests/baselines/reference/definePropertyES5.symbols

@@ -5,11 +5,14 @@ var x: "p" = "p"
 class A {
 >A : Symbol(A, Decl(definePropertyES5.ts, 0, 16))
 
-    a = 12
+    a = this.y
 >a : Symbol(A.a, Decl(definePropertyES5.ts, 1, 9))
+>this.y : Symbol(A.y, Decl(definePropertyES5.ts, 7, 16))
+>this : Symbol(A, Decl(definePropertyES5.ts, 0, 16))
+>y : Symbol(A.y, Decl(definePropertyES5.ts, 7, 16))
 
     b
->b : Symbol(A.b, Decl(definePropertyES5.ts, 2, 10))
+>b : Symbol(A.b, Decl(definePropertyES5.ts, 2, 14))
 
     ["computed"] = 13
 >["computed"] : Symbol(A["computed"], Decl(definePropertyES5.ts, 3, 5))
@@ -21,5 +24,14 @@ class A {
 
     m() { }
 >m : Symbol(A.m, Decl(definePropertyES5.ts, 5, 13))
+
+    constructor(public readonly y: number) { }
+>y : Symbol(A.y, Decl(definePropertyES5.ts, 7, 16))
+
+    z = this.y
+>z : Symbol(A.z, Decl(definePropertyES5.ts, 7, 46))
+>this.y : Symbol(A.y, Decl(definePropertyES5.ts, 7, 16))
+>this : Symbol(A, Decl(definePropertyES5.ts, 0, 16))
+>y : Symbol(A.y, Decl(definePropertyES5.ts, 7, 16))
 }
 

tests/baselines/reference/definePropertyES5.types

@@ -6,9 +6,11 @@ var x: "p" = "p"
 class A {
 >A : A
 
-    a = 12
+    a = this.y
 >a : number
->12 : 12
+>this.y : number
+>this : this
+>y : number
 
     b
 >b : any
@@ -25,5 +27,14 @@ class A {
 
     m() { }
 >m : () => void
+
+    constructor(public readonly y: number) { }
+>y : number
+
+    z = this.y
+>z : number
+>this.y : number
+>this : this
+>y : number
 }
 

tests/baselines/reference/definePropertyESNext.js

@@ -0,0 +1,45 @@
+//// [definePropertyESNext.ts]
+var x: "p" = "p"
+class A {
+    a = 12
+    b
+    ["computed"] = 13
+    ;[x] = 14
+    m() { }
+    constructor(public readonly y: number) { }
+}
+class B {
+}
+class C extends B {
+    z = this.ka
+    constructor(public ka: number) {
+        super()
+    }
+    ki = this.ka
+}
+
+
+//// [definePropertyESNext.js]
+var x = "p";
+class A {
+    y;
+    a = 12;
+    b;
+    ["computed"] = 13;
+    [x] = 14;
+    m() { }
+    constructor(y) {
+        this.y = y;
+    }
+}
+class B {
+}
+class C extends B {
+    ka;
+    z = this.ka;
+    constructor(ka) {
+        super();
+        this.ka = ka;
+    }
+    ki = this.ka;
+}

tests/baselines/reference/definePropertyESNext.symbols

@@ -0,0 +1,53 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/definePropertyESNext.ts ===
+var x: "p" = "p"
+>x : Symbol(x, Decl(definePropertyESNext.ts, 0, 3))
+
+class A {
+>A : Symbol(A, Decl(definePropertyESNext.ts, 0, 16))
+
+    a = 12
+>a : Symbol(A.a, Decl(definePropertyESNext.ts, 1, 9))
+
+    b
+>b : Symbol(A.b, Decl(definePropertyESNext.ts, 2, 10))
+
+    ["computed"] = 13
+>["computed"] : Symbol(A["computed"], Decl(definePropertyESNext.ts, 3, 5))
+>"computed" : Symbol(A["computed"], Decl(definePropertyESNext.ts, 3, 5))
+
+    ;[x] = 14
+>[x] : Symbol(A[x], Decl(definePropertyESNext.ts, 5, 5))
+>x : Symbol(x, Decl(definePropertyESNext.ts, 0, 3))
+
+    m() { }
+>m : Symbol(A.m, Decl(definePropertyESNext.ts, 5, 13))
+
+    constructor(public readonly y: number) { }
+>y : Symbol(A.y, Decl(definePropertyESNext.ts, 7, 16))
+}
+class B {
+>B : Symbol(B, Decl(definePropertyESNext.ts, 8, 1))
+}
+class C extends B {
+>C : Symbol(C, Decl(definePropertyESNext.ts, 10, 1))
+>B : Symbol(B, Decl(definePropertyESNext.ts, 8, 1))
+
+    z = this.ka
+>z : Symbol(C.z, Decl(definePropertyESNext.ts, 11, 19))
+>this.ka : Symbol(C.ka, Decl(definePropertyESNext.ts, 13, 16))
+>this : Symbol(C, Decl(definePropertyESNext.ts, 10, 1))
+>ka : Symbol(C.ka, Decl(definePropertyESNext.ts, 13, 16))
+
+    constructor(public ka: number) {
+>ka : Symbol(C.ka, Decl(definePropertyESNext.ts, 13, 16))
+
+        super()
+>super : Symbol(B, Decl(definePropertyESNext.ts, 8, 1))
+    }
+    ki = this.ka
+>ki : Symbol(C.ki, Decl(definePropertyESNext.ts, 15, 5))
+>this.ka : Symbol(C.ka, Decl(definePropertyESNext.ts, 13, 16))
+>this : Symbol(C, Decl(definePropertyESNext.ts, 10, 1))
+>ka : Symbol(C.ka, Decl(definePropertyESNext.ts, 13, 16))
+}
+

tests/baselines/reference/definePropertyESNext.types

@@ -0,0 +1,58 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/definePropertyESNext.ts ===
+var x: "p" = "p"
+>x : "p"
+>"p" : "p"
+
+class A {
+>A : A
+
+    a = 12
+>a : number
+>12 : 12
+
+    b
+>b : any
+
+    ["computed"] = 13
+>["computed"] : number
+>"computed" : "computed"
+>13 : 13
+
+    ;[x] = 14
+>[x] : number
+>x : "p"
+>14 : 14
+
+    m() { }
+>m : () => void
+
+    constructor(public readonly y: number) { }
+>y : number
+}
+class B {
+>B : B
+}
+class C extends B {
+>C : C
+>B : B
+
+    z = this.ka
+>z : number
+>this.ka : number
+>this : this
+>ka : number
+
+    constructor(public ka: number) {
+>ka : number
+
+        super()
+>super() : void
+>super : typeof B
+    }
+    ki = this.ka
+>ki : number
+>this.ka : number
+>this : this
+>ka : number
+}
+

tests/cases/conformance/classes/propertyMemberDeclarations/definePropertyES5.ts

@@ -2,9 +2,11 @@
 // @useDefineForClassFields: true
 var x: "p" = "p"
 class A {
-    a = 12
+    a = this.y
     b
     ["computed"] = 13
     ;[x] = 14
     m() { }
+    constructor(public readonly y: number) { }
+    z = this.y
 }

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

@@ -0,0 +1,20 @@
+// @target: esnext
+// @useDefineForClassFields: true
+var x: "p" = "p"
+class A {
+    a = 12
+    b
+    ["computed"] = 13
+    ;[x] = 14
+    m() { }
+    constructor(public readonly y: number) { }
+}
+class B {
+}
+class C extends B {
+    z = this.ka
+    constructor(public ka: number) {
+        super()
+    }
+    ki = this.ka
+}