From 5b77ef8b4d42ee7ed3a80ee8326fa9c622c3c5cb Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wwigham@gmail.com>
Date: Wed, 26 Jul 2017 10:12:59 -0700
Subject: [PATCH] Fix infinite loop in jsdoc parsing (#17420)

* Test case

* Move parameter fix to apply to jsdoc (and all lists)

* Inline function, generalize comment
---
 src/compiler/parser.ts                        | 19 ++++++++++---------
 ...docParameterParsingInfiniteLoop.errors.txt | 11 +++++++++++
 .../jsdocParameterParsingInfiniteLoop.ts      |  9 +++++++++
 3 files changed, 30 insertions(+), 9 deletions(-)
 create mode 100644 tests/baselines/reference/jsdocParameterParsingInfiniteLoop.errors.txt
 create mode 100644 tests/cases/compiler/jsdocParameterParsingInfiniteLoop.ts

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 9c725a5d6e7..5d6cd9e3bd1 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -1865,9 +1865,12 @@ namespace ts {
             let commaStart = -1; // Meaning the previous token was not a comma
             while (true) {
                 if (isListElement(kind, /*inErrorRecovery*/ false)) {
+                    const startPos = scanner.getStartPos();
                     result.push(parseListElement(kind, parseElement));
                     commaStart = scanner.getTokenPos();
+
                     if (parseOptional(SyntaxKind.CommaToken)) {
+                        // No need to check for a zero length node since we know we parsed a comma
                         continue;
                     }
 
@@ -1888,6 +1891,13 @@ namespace ts {
                     if (considerSemicolonAsDelimiter && token() === SyntaxKind.SemicolonToken && !scanner.hasPrecedingLineBreak()) {
                         nextToken();
                     }
+                    if (startPos === scanner.getStartPos()) {
+                        // What we're parsing isn't actually remotely recognizable as a element and we've consumed no tokens whatsoever
+                        // Consume a token to advance the parser in some way and avoid an infinite loop
+                        // This can happen when we're speculatively parsing parenthesized expressions which we think may be arrow functions,
+                        // or when a modifier keyword which is disallowed as a parameter name (ie, `static` in strict mode) is supplied
+                        nextToken();
+                    }
                     continue;
                 }
 
@@ -2221,7 +2231,6 @@ namespace ts {
                 return finishNode(node);
             }
 
-            const startPos = scanner.getStartPos();
             node.decorators = parseDecorators();
             node.modifiers = parseModifiers();
             node.dotDotDotToken = parseOptionalToken(SyntaxKind.DotDotDotToken);
@@ -2245,14 +2254,6 @@ namespace ts {
             node.type = parseParameterType();
             node.initializer = parseBindingElementInitializer(/*inParameter*/ true);
 
-            if (startPos === scanner.getStartPos()) {
-                // What we're parsing isn't actually remotely recognizable as a parameter and we've consumed no tokens whatsoever
-                // Consume a token to advance the parser in some way and avoid an infinite loop in `parseDelimitedList`
-                // This can happen when we're speculatively parsing parenthesized expressions which we think may be arrow functions,
-                // or when a modifier keyword which is disallowed as a parameter name (ie, `static` in strict mode) is supplied
-                nextToken();
-            }
-
             return addJSDocComment(finishNode(node));
         }
 
diff --git a/tests/baselines/reference/jsdocParameterParsingInfiniteLoop.errors.txt b/tests/baselines/reference/jsdocParameterParsingInfiniteLoop.errors.txt
new file mode 100644
index 00000000000..e42d67a62c1
--- /dev/null
+++ b/tests/baselines/reference/jsdocParameterParsingInfiniteLoop.errors.txt
@@ -0,0 +1,11 @@
+tests/cases/compiler/example.js(3,20): error TS1003: Identifier expected.
+
+
+==== tests/cases/compiler/example.js (1 errors) ====
+    // @ts-check
+    /**
+     * @type {function(@foo)}
+                       ~
+!!! error TS1003: Identifier expected.
+     */
+    let x;
\ No newline at end of file
diff --git a/tests/cases/compiler/jsdocParameterParsingInfiniteLoop.ts b/tests/cases/compiler/jsdocParameterParsingInfiniteLoop.ts
new file mode 100644
index 00000000000..581a485bf0b
--- /dev/null
+++ b/tests/cases/compiler/jsdocParameterParsingInfiniteLoop.ts
@@ -0,0 +1,9 @@
+// @filename: example.js
+// @checkJs: true
+// @allowJs: true
+// @noEmit: true
+// @ts-check
+/**
+ * @type {function(@foo)}
+ */
+let x;
\ No newline at end of file