From cf53743bd696de5b3a3eff71a13b799c8e390ea7 Mon Sep 17 00:00:00 2001
From: Andy <anhans@microsoft.com>
Date: Thu, 14 Sep 2017 07:59:53 -0700
Subject: [PATCH] In `isInPropertyInitializer`, don't bail out at a
 `PropertyAssignment` (#18449)

---
 src/compiler/checker.ts                        | 16 +++++++++++++++-
 ...reDeclaration_propertyAssignment.errors.txt | 11 +++++++++++
 .../useBeforeDeclaration_propertyAssignment.js | 18 ++++++++++++++++++
 .../useBeforeDeclaration_propertyAssignment.ts |  4 ++++
 4 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/useBeforeDeclaration_propertyAssignment.errors.txt
 create mode 100644 tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js
 create mode 100644 tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5c6a8b59119..1fae08328b3 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -14753,7 +14753,7 @@ namespace ts {
                 return;
             }
 
-            if (findAncestor(node, node => node.kind === SyntaxKind.PropertyDeclaration ? true : isExpression(node) ? false : "quit") &&
+            if (isInPropertyInitializer(node) &&
                 !isBlockScopedNameDeclaredBeforeUse(valueDeclaration, right)
                 && !isPropertyDeclaredInAncestorClass(prop)) {
                 error(right, Diagnostics.Block_scoped_variable_0_used_before_its_declaration, unescapeLeadingUnderscores(right.escapedText));
@@ -14766,6 +14766,20 @@ namespace ts {
             }
         }
 
+        function isInPropertyInitializer(node: Node): boolean {
+            return !!findAncestor(node, node => {
+                switch (node.kind) {
+                    case SyntaxKind.PropertyDeclaration:
+                        return true;
+                    case SyntaxKind.PropertyAssignment:
+                        // We might be in `a = { b: this.b }`, so keep looking. See `tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts`.
+                        return false;
+                    default:
+                        return isPartOfExpression(node) ? false : "quit";
+                }
+            });
+        }
+
         /**
          * It's possible that "prop.valueDeclaration" is a local declaration, but the property was also declared in a superclass.
          * In that case we won't consider it used before its declaration, because it gets its value from the superclass' declaration.
diff --git a/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.errors.txt b/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.errors.txt
new file mode 100644
index 00000000000..f237fd07c80
--- /dev/null
+++ b/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.errors.txt
@@ -0,0 +1,11 @@
+tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts(2,27): error TS2448: Block-scoped variable 'b' used before its declaration.
+
+
+==== tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts (1 errors) ====
+    export class C {
+        public a =  { b: this.b };
+                              ~
+!!! error TS2448: Block-scoped variable 'b' used before its declaration.
+        private b = 0;
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js b/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js
new file mode 100644
index 00000000000..e34604e0a4e
--- /dev/null
+++ b/tests/baselines/reference/useBeforeDeclaration_propertyAssignment.js
@@ -0,0 +1,18 @@
+//// [useBeforeDeclaration_propertyAssignment.ts]
+export class C {
+    public a =  { b: this.b };
+    private b = 0;
+}
+
+
+//// [useBeforeDeclaration_propertyAssignment.js]
+"use strict";
+exports.__esModule = true;
+var C = /** @class */ (function () {
+    function C() {
+        this.a = { b: this.b };
+        this.b = 0;
+    }
+    return C;
+}());
+exports.C = C;
diff --git a/tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts b/tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts
new file mode 100644
index 00000000000..bdd84473c57
--- /dev/null
+++ b/tests/cases/compiler/useBeforeDeclaration_propertyAssignment.ts
@@ -0,0 +1,4 @@
+export class C {
+    public a =  { b: this.b };
+    private b = 0;
+}