From 53105b3afff2b3e054d5e3f2ff013d124ae783b4 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Tue, 25 Sep 2018 16:06:23 -0700
Subject: [PATCH] Fix crash in use-before-def checking of enum tag (#27350)

---
 src/compiler/checker.ts                            |  4 +++-
 .../reference/enumTagUseBeforeDefCrash.symbols     | 13 +++++++++++++
 .../reference/enumTagUseBeforeDefCrash.types       | 14 ++++++++++++++
 .../conformance/jsdoc/enumTagUseBeforeDefCrash.ts  | 13 +++++++++++++
 4 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/enumTagUseBeforeDefCrash.symbols
 create mode 100644 tests/baselines/reference/enumTagUseBeforeDefCrash.types
 create mode 100644 tests/cases/conformance/jsdoc/enumTagUseBeforeDefCrash.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d5eda73b4d1af..86bc7ec1d16b5 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1707,7 +1707,9 @@ namespace ts {
         function checkResolvedBlockScopedVariable(result: Symbol, errorLocation: Node): void {
             Debug.assert(!!(result.flags & SymbolFlags.BlockScopedVariable || result.flags & SymbolFlags.Class || result.flags & SymbolFlags.Enum));
             // Block-scoped variables cannot be used before their definition
-            const declaration = forEach(result.declarations, d => isBlockOrCatchScoped(d) || isClassLike(d) || (d.kind === SyntaxKind.EnumDeclaration) ? d : undefined);
+            const declaration = find(
+                result.declarations,
+                d => isBlockOrCatchScoped(d) || isClassLike(d) || (d.kind === SyntaxKind.EnumDeclaration) || isInJSFile(d) && !!getJSDocEnumTag(d));
 
             if (declaration === undefined) return Debug.fail("Declaration to checkResolvedBlockScopedVariable is undefined");
 
diff --git a/tests/baselines/reference/enumTagUseBeforeDefCrash.symbols b/tests/baselines/reference/enumTagUseBeforeDefCrash.symbols
new file mode 100644
index 0000000000000..1cef96a9823a7
--- /dev/null
+++ b/tests/baselines/reference/enumTagUseBeforeDefCrash.symbols
@@ -0,0 +1,13 @@
+=== tests/cases/conformance/jsdoc/bug27134.js ===
+/**
+ * @enum {number}
+ */
+var foo = { };
+>foo : Symbol(foo, Decl(bug27134.js, 3, 3))
+
+/**
+ * @type {foo}
+ */
+var s;
+>s : Symbol(s, Decl(bug27134.js, 8, 3))
+
diff --git a/tests/baselines/reference/enumTagUseBeforeDefCrash.types b/tests/baselines/reference/enumTagUseBeforeDefCrash.types
new file mode 100644
index 0000000000000..159781fee05f1
--- /dev/null
+++ b/tests/baselines/reference/enumTagUseBeforeDefCrash.types
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/jsdoc/bug27134.js ===
+/**
+ * @enum {number}
+ */
+var foo = { };
+>foo : typeof foo
+>{ } : {}
+
+/**
+ * @type {foo}
+ */
+var s;
+>s : number
+
diff --git a/tests/cases/conformance/jsdoc/enumTagUseBeforeDefCrash.ts b/tests/cases/conformance/jsdoc/enumTagUseBeforeDefCrash.ts
new file mode 100644
index 0000000000000..f8f92b7bcc1bf
--- /dev/null
+++ b/tests/cases/conformance/jsdoc/enumTagUseBeforeDefCrash.ts
@@ -0,0 +1,13 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @Filename: bug27134.js
+/**
+ * @enum {number}
+ */
+var foo = { };
+
+/**
+ * @type {foo}
+ */
+var s;