Added error for class properties used within their own declaration (#29395)

* Added error for class properties used within their own declaration

Fixes #5987.

Usages of a class property in a preceding property already gave an error, but the following doesn't yet:

```ts
class Test {
    x: number = this.x;
}
```

As with other use-before-declare checking, IIFEs are not treated as invalid uses.

* Accepted 'witness' baselines; removed unnecessary !==

* Addressed quick feedback items

* Accepted odd new baseline

* Fixed post-merge introduced lint errors

* Updated baselines again

Author: sandersn

Diff for: src/compiler/checker.ts

@@ -1130,6 +1130,10 @@ namespace ts {
                     // still might be illegal if the usage is within a computed property name in the class (eg class A { static p = "a"; [A.p]() {} })
                     return !findAncestor(usage, n => isComputedPropertyName(n) && n.parent.parent === declaration);
                 }
+                else if (isPropertyDeclaration(declaration)) {
+                    // still might be illegal if a self-referencing property initializer (eg private x = this.x)
+                    return !isPropertyImmediatelyReferencedWithinDeclaration(declaration, usage);
+                }
                 return true;
             }
 
@@ -1204,6 +1208,40 @@ namespace ts {
                     return false;
                 });
             }
+
+            function isPropertyImmediatelyReferencedWithinDeclaration(declaration: PropertyDeclaration, usage: Node) {
+                // always legal if usage is after declaration
+                if (usage.end > declaration.end) {
+                    return false;
+                }
+
+                // still might be legal if usage is deferred (e.g. x: any = () => this.x)
+                // otherwise illegal if immediately referenced within the declaration (e.g. x: any = this.x)
+                const ancestorChangingReferenceScope = findAncestor(usage, (node: Node) => {
+                    if (node === declaration) {
+                        return "quit";
+                    }
+
+                    switch (node.kind) {
+                        case SyntaxKind.ArrowFunction:
+                        case SyntaxKind.PropertyDeclaration:
+                            return true;
+                        case SyntaxKind.Block:
+                            switch (node.parent.kind) {
+                                case SyntaxKind.GetAccessor:
+                                case SyntaxKind.MethodDeclaration:
+                                case SyntaxKind.SetAccessor:
+                                    return true;
+                                default:
+                                    return false;
+                            }
+                        default:
+                            return false;
+                    }
+                });
+
+                return ancestorChangingReferenceScope === undefined;
+            }
         }
 
         /**

Diff for: tests/baselines/reference/classUsedBeforeInitializedVariables.errors.txt

@@ -0,0 +1,66 @@
+tests/cases/compiler/classUsedBeforeInitializedVariables.ts(4,15): error TS2729: Property 'p4' is used before its initialization.
+tests/cases/compiler/classUsedBeforeInitializedVariables.ts(7,34): error TS2729: Property 'directlyAssigned' is used before its initialization.
+tests/cases/compiler/classUsedBeforeInitializedVariables.ts(16,15): error TS2729: Property 'withinObjectLiteral' is used before its initialization.
+tests/cases/compiler/classUsedBeforeInitializedVariables.ts(20,19): error TS2729: Property 'withinObjectLiteralGetterName' is used before its initialization.
+tests/cases/compiler/classUsedBeforeInitializedVariables.ts(26,19): error TS2729: Property 'withinObjectLiteralSetterName' is used before its initialization.
+tests/cases/compiler/classUsedBeforeInitializedVariables.ts(29,64): error TS2729: Property 'withinClassDeclarationExtension' is used before its initialization.
+
+
+==== tests/cases/compiler/classUsedBeforeInitializedVariables.ts (6 errors) ====
+    class Test {
+        p1 = 0;
+        p2 = this.p1;
+        p3 = this.p4;
+                  ~~
+!!! error TS2729: Property 'p4' is used before its initialization.
+!!! related TS2728 tests/cases/compiler/classUsedBeforeInitializedVariables.ts:5:5: 'p4' is declared here.
+        p4 = 0;
+    
+        directlyAssigned: any = this.directlyAssigned;
+                                     ~~~~~~~~~~~~~~~~
+!!! error TS2729: Property 'directlyAssigned' is used before its initialization.
+!!! related TS2728 tests/cases/compiler/classUsedBeforeInitializedVariables.ts:7:5: 'directlyAssigned' is declared here.
+    
+        withinArrowFunction: any = () => this.withinArrowFunction;
+    
+        withinFunction: any = function () {
+            return this.withinFunction;
+        };
+    
+        withinObjectLiteral: any = {
+            [this.withinObjectLiteral]: true,
+                  ~~~~~~~~~~~~~~~~~~~
+!!! error TS2729: Property 'withinObjectLiteral' is used before its initialization.
+!!! related TS2728 tests/cases/compiler/classUsedBeforeInitializedVariables.ts:15:5: 'withinObjectLiteral' is declared here.
+        };
+    
+        withinObjectLiteralGetterName: any = {
+            get [this.withinObjectLiteralGetterName]() {
+                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2729: Property 'withinObjectLiteralGetterName' is used before its initialization.
+!!! related TS2728 tests/cases/compiler/classUsedBeforeInitializedVariables.ts:19:5: 'withinObjectLiteralGetterName' is declared here.
+                return true;
+            }
+        };
+    
+        withinObjectLiteralSetterName: any = {
+            set [this.withinObjectLiteralSetterName](_: any) {}
+                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2729: Property 'withinObjectLiteralSetterName' is used before its initialization.
+!!! related TS2728 tests/cases/compiler/classUsedBeforeInitializedVariables.ts:25:5: 'withinObjectLiteralSetterName' is declared here.
+        };
+    
+        withinClassDeclarationExtension: any = (class extends this.withinClassDeclarationExtension { });
+                                                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2729: Property 'withinClassDeclarationExtension' is used before its initialization.
+!!! related TS2728 tests/cases/compiler/classUsedBeforeInitializedVariables.ts:29:5: 'withinClassDeclarationExtension' is declared here.
+    
+        // These error cases are ignored (not checked by control flow analysis)
+    
+        assignedByArrowFunction: any = (() => this.assignedByFunction)();
+    
+        assignedByFunction: any = (function () {
+            return this.assignedByFunction;
+        })();
+    }
+    

Diff for: tests/baselines/reference/classUsedBeforeInitializedVariables.js

@@ -0,0 +1,102 @@
+//// [classUsedBeforeInitializedVariables.ts]
+class Test {
+    p1 = 0;
+    p2 = this.p1;
+    p3 = this.p4;
+    p4 = 0;
+
+    directlyAssigned: any = this.directlyAssigned;
+
+    withinArrowFunction: any = () => this.withinArrowFunction;
+
+    withinFunction: any = function () {
+        return this.withinFunction;
+    };
+
+    withinObjectLiteral: any = {
+        [this.withinObjectLiteral]: true,
+    };
+
+    withinObjectLiteralGetterName: any = {
+        get [this.withinObjectLiteralGetterName]() {
+            return true;
+        }
+    };
+
+    withinObjectLiteralSetterName: any = {
+        set [this.withinObjectLiteralSetterName](_: any) {}
+    };
+
+    withinClassDeclarationExtension: any = (class extends this.withinClassDeclarationExtension { });
+
+    // These error cases are ignored (not checked by control flow analysis)
+
+    assignedByArrowFunction: any = (() => this.assignedByFunction)();
+
+    assignedByFunction: any = (function () {
+        return this.assignedByFunction;
+    })();
+}
+
+
+//// [classUsedBeforeInitializedVariables.js]
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = function (d, b) {
+        extendStatics = Object.setPrototypeOf ||
+            ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+            function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+        return extendStatics(d, b);
+    };
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+var Test = /** @class */ (function () {
+    function Test() {
+        var _a, _b, _c;
+        var _this = this;
+        this.p1 = 0;
+        this.p2 = this.p1;
+        this.p3 = this.p4;
+        this.p4 = 0;
+        this.directlyAssigned = this.directlyAssigned;
+        this.withinArrowFunction = function () { return _this.withinArrowFunction; };
+        this.withinFunction = function () {
+            return this.withinFunction;
+        };
+        this.withinObjectLiteral = (_a = {},
+            _a[this.withinObjectLiteral] = true,
+            _a);
+        this.withinObjectLiteralGetterName = (_b = {},
+            Object.defineProperty(_b, this.withinObjectLiteralGetterName, {
+                get: function () {
+                    return true;
+                },
+                enumerable: true,
+                configurable: true
+            }),
+            _b);
+        this.withinObjectLiteralSetterName = (_c = {},
+            Object.defineProperty(_c, this.withinObjectLiteralSetterName, {
+                set: function (_) { },
+                enumerable: true,
+                configurable: true
+            }),
+            _c);
+        this.withinClassDeclarationExtension = (/** @class */ (function (_super) {
+            __extends(class_1, _super);
+            function class_1() {
+                return _super !== null && _super.apply(this, arguments) || this;
+            }
+            return class_1;
+        }(this.withinClassDeclarationExtension)));
+        // These error cases are ignored (not checked by control flow analysis)
+        this.assignedByArrowFunction = (function () { return _this.assignedByFunction; })();
+        this.assignedByFunction = (function () {
+            return this.assignedByFunction;
+        })();
+    }
+    return Test;
+}());

Diff for: tests/baselines/reference/classUsedBeforeInitializedVariables.symbols

@@ -0,0 +1,97 @@
+=== tests/cases/compiler/classUsedBeforeInitializedVariables.ts ===
+class Test {
+>Test : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+
+    p1 = 0;
+>p1 : Symbol(Test.p1, Decl(classUsedBeforeInitializedVariables.ts, 0, 12))
+
+    p2 = this.p1;
+>p2 : Symbol(Test.p2, Decl(classUsedBeforeInitializedVariables.ts, 1, 11))
+>this.p1 : Symbol(Test.p1, Decl(classUsedBeforeInitializedVariables.ts, 0, 12))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>p1 : Symbol(Test.p1, Decl(classUsedBeforeInitializedVariables.ts, 0, 12))
+
+    p3 = this.p4;
+>p3 : Symbol(Test.p3, Decl(classUsedBeforeInitializedVariables.ts, 2, 17))
+>this.p4 : Symbol(Test.p4, Decl(classUsedBeforeInitializedVariables.ts, 3, 17))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>p4 : Symbol(Test.p4, Decl(classUsedBeforeInitializedVariables.ts, 3, 17))
+
+    p4 = 0;
+>p4 : Symbol(Test.p4, Decl(classUsedBeforeInitializedVariables.ts, 3, 17))
+
+    directlyAssigned: any = this.directlyAssigned;
+>directlyAssigned : Symbol(Test.directlyAssigned, Decl(classUsedBeforeInitializedVariables.ts, 4, 11))
+>this.directlyAssigned : Symbol(Test.directlyAssigned, Decl(classUsedBeforeInitializedVariables.ts, 4, 11))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>directlyAssigned : Symbol(Test.directlyAssigned, Decl(classUsedBeforeInitializedVariables.ts, 4, 11))
+
+    withinArrowFunction: any = () => this.withinArrowFunction;
+>withinArrowFunction : Symbol(Test.withinArrowFunction, Decl(classUsedBeforeInitializedVariables.ts, 6, 50))
+>this.withinArrowFunction : Symbol(Test.withinArrowFunction, Decl(classUsedBeforeInitializedVariables.ts, 6, 50))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>withinArrowFunction : Symbol(Test.withinArrowFunction, Decl(classUsedBeforeInitializedVariables.ts, 6, 50))
+
+    withinFunction: any = function () {
+>withinFunction : Symbol(Test.withinFunction, Decl(classUsedBeforeInitializedVariables.ts, 8, 62))
+
+        return this.withinFunction;
+    };
+
+    withinObjectLiteral: any = {
+>withinObjectLiteral : Symbol(Test.withinObjectLiteral, Decl(classUsedBeforeInitializedVariables.ts, 12, 6))
+
+        [this.withinObjectLiteral]: true,
+>[this.withinObjectLiteral] : Symbol([this.withinObjectLiteral], Decl(classUsedBeforeInitializedVariables.ts, 14, 32))
+>this.withinObjectLiteral : Symbol(Test.withinObjectLiteral, Decl(classUsedBeforeInitializedVariables.ts, 12, 6))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>withinObjectLiteral : Symbol(Test.withinObjectLiteral, Decl(classUsedBeforeInitializedVariables.ts, 12, 6))
+
+    };
+
+    withinObjectLiteralGetterName: any = {
+>withinObjectLiteralGetterName : Symbol(Test.withinObjectLiteralGetterName, Decl(classUsedBeforeInitializedVariables.ts, 16, 6))
+
+        get [this.withinObjectLiteralGetterName]() {
+>[this.withinObjectLiteralGetterName] : Symbol([this.withinObjectLiteralGetterName], Decl(classUsedBeforeInitializedVariables.ts, 18, 42))
+>this.withinObjectLiteralGetterName : Symbol(Test.withinObjectLiteralGetterName, Decl(classUsedBeforeInitializedVariables.ts, 16, 6))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>withinObjectLiteralGetterName : Symbol(Test.withinObjectLiteralGetterName, Decl(classUsedBeforeInitializedVariables.ts, 16, 6))
+
+            return true;
+        }
+    };
+
+    withinObjectLiteralSetterName: any = {
+>withinObjectLiteralSetterName : Symbol(Test.withinObjectLiteralSetterName, Decl(classUsedBeforeInitializedVariables.ts, 22, 6))
+
+        set [this.withinObjectLiteralSetterName](_: any) {}
+>[this.withinObjectLiteralSetterName] : Symbol([this.withinObjectLiteralSetterName], Decl(classUsedBeforeInitializedVariables.ts, 24, 42))
+>this.withinObjectLiteralSetterName : Symbol(Test.withinObjectLiteralSetterName, Decl(classUsedBeforeInitializedVariables.ts, 22, 6))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>withinObjectLiteralSetterName : Symbol(Test.withinObjectLiteralSetterName, Decl(classUsedBeforeInitializedVariables.ts, 22, 6))
+>_ : Symbol(_, Decl(classUsedBeforeInitializedVariables.ts, 25, 49))
+
+    };
+
+    withinClassDeclarationExtension: any = (class extends this.withinClassDeclarationExtension { });
+>withinClassDeclarationExtension : Symbol(Test.withinClassDeclarationExtension, Decl(classUsedBeforeInitializedVariables.ts, 26, 6))
+>this.withinClassDeclarationExtension : Symbol(Test.withinClassDeclarationExtension, Decl(classUsedBeforeInitializedVariables.ts, 26, 6))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>withinClassDeclarationExtension : Symbol(Test.withinClassDeclarationExtension, Decl(classUsedBeforeInitializedVariables.ts, 26, 6))
+
+    // These error cases are ignored (not checked by control flow analysis)
+
+    assignedByArrowFunction: any = (() => this.assignedByFunction)();
+>assignedByArrowFunction : Symbol(Test.assignedByArrowFunction, Decl(classUsedBeforeInitializedVariables.ts, 28, 100))
+>this.assignedByFunction : Symbol(Test.assignedByFunction, Decl(classUsedBeforeInitializedVariables.ts, 32, 69))
+>this : Symbol(Test, Decl(classUsedBeforeInitializedVariables.ts, 0, 0))
+>assignedByFunction : Symbol(Test.assignedByFunction, Decl(classUsedBeforeInitializedVariables.ts, 32, 69))
+
+    assignedByFunction: any = (function () {
+>assignedByFunction : Symbol(Test.assignedByFunction, Decl(classUsedBeforeInitializedVariables.ts, 32, 69))
+
+        return this.assignedByFunction;
+    })();
+}
+