From 9ca13c7042089765abc789f26e9cfe848a0186e4 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Thu, 26 Jan 2023 19:15:13 -0800
Subject: [PATCH 1/6] Add failing tests

---
 tests/cases/fourslash/jsxElementExtendsNoCrash1.ts | 6 ++++++
 tests/cases/fourslash/jsxElementExtendsNoCrash2.ts | 6 ++++++
 2 files changed, 12 insertions(+)
 create mode 100644 tests/cases/fourslash/jsxElementExtendsNoCrash1.ts
 create mode 100644 tests/cases/fourslash/jsxElementExtendsNoCrash2.ts

diff --git a/tests/cases/fourslash/jsxElementExtendsNoCrash1.ts b/tests/cases/fourslash/jsxElementExtendsNoCrash1.ts
new file mode 100644
index 0000000000000..6959cc9ce40e8
--- /dev/null
+++ b/tests/cases/fourslash/jsxElementExtendsNoCrash1.ts
@@ -0,0 +1,6 @@
+/// <reference path="fourslash.ts" />
+
+// @filename: index.tsx
+//// <const T extends/>
+
+verify.getSuggestionDiagnostics([]);
diff --git a/tests/cases/fourslash/jsxElementExtendsNoCrash2.ts b/tests/cases/fourslash/jsxElementExtendsNoCrash2.ts
new file mode 100644
index 0000000000000..4c42f85626517
--- /dev/null
+++ b/tests/cases/fourslash/jsxElementExtendsNoCrash2.ts
@@ -0,0 +1,6 @@
+/// <reference path="fourslash.ts" />
+
+// @filename: index.tsx
+//// <T extends/>
+
+verify.getSuggestionDiagnostics([]);

From a122a31e7f4d0bfa30887d718a0ef765a8bcce57 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Thu, 26 Jan 2023 19:20:12 -0800
Subject: [PATCH 2/6] Add plain parser test

---
 .../reference/parseJsxExtends1.errors.txt        | 13 +++++++++++++
 tests/baselines/reference/parseJsxExtends1.js    | 16 ++++++++++++++++
 .../baselines/reference/parseJsxExtends1.symbols |  8 ++++++++
 tests/baselines/reference/parseJsxExtends1.types | 10 ++++++++++
 .../reference/parseJsxExtends2.errors.txt        | 13 +++++++++++++
 tests/baselines/reference/parseJsxExtends2.js    | 16 ++++++++++++++++
 .../baselines/reference/parseJsxExtends2.symbols |  8 ++++++++
 tests/baselines/reference/parseJsxExtends2.types | 10 ++++++++++
 tests/cases/compiler/parseJsxExtends1.ts         |  6 ++++++
 tests/cases/compiler/parseJsxExtends2.ts         |  6 ++++++
 10 files changed, 106 insertions(+)
 create mode 100644 tests/baselines/reference/parseJsxExtends1.errors.txt
 create mode 100644 tests/baselines/reference/parseJsxExtends1.js
 create mode 100644 tests/baselines/reference/parseJsxExtends1.symbols
 create mode 100644 tests/baselines/reference/parseJsxExtends1.types
 create mode 100644 tests/baselines/reference/parseJsxExtends2.errors.txt
 create mode 100644 tests/baselines/reference/parseJsxExtends2.js
 create mode 100644 tests/baselines/reference/parseJsxExtends2.symbols
 create mode 100644 tests/baselines/reference/parseJsxExtends2.types
 create mode 100644 tests/cases/compiler/parseJsxExtends1.ts
 create mode 100644 tests/cases/compiler/parseJsxExtends2.ts

diff --git a/tests/baselines/reference/parseJsxExtends1.errors.txt b/tests/baselines/reference/parseJsxExtends1.errors.txt
new file mode 100644
index 0000000000000..617d4927aac5a
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends1.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/index.tsx(2,29): error TS1161: Unterminated regular expression literal.
+tests/cases/compiler/index.tsx(3,1): error TS1005: ',' expected.
+
+
+==== tests/cases/compiler/index.tsx (2 errors) ====
+    export function Foo() {
+        return <const T extends/>
+                                
+!!! error TS1161: Unterminated regular expression literal.
+    }
+    ~
+!!! error TS1005: ',' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/parseJsxExtends1.js b/tests/baselines/reference/parseJsxExtends1.js
new file mode 100644
index 0000000000000..542b7f726fc4f
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends1.js
@@ -0,0 +1,16 @@
+//// [index.tsx]
+export function Foo() {
+    return <const T extends/>
+}
+
+
+//// [index.jsx]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.Foo = void 0;
+function Foo() {
+    return function () {
+        return ;
+    };
+}
+exports.Foo = Foo;
diff --git a/tests/baselines/reference/parseJsxExtends1.symbols b/tests/baselines/reference/parseJsxExtends1.symbols
new file mode 100644
index 0000000000000..ef7299a5c9837
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends1.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/index.tsx ===
+export function Foo() {
+>Foo : Symbol(Foo, Decl(index.tsx, 0, 0))
+
+    return <const T extends/>
+>T : Symbol(T, Decl(index.tsx, 1, 12))
+}
+
diff --git a/tests/baselines/reference/parseJsxExtends1.types b/tests/baselines/reference/parseJsxExtends1.types
new file mode 100644
index 0000000000000..03425efb2db40
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends1.types
@@ -0,0 +1,10 @@
+=== tests/cases/compiler/index.tsx ===
+export function Foo() {
+>Foo : () => <const T>() => any
+
+    return <const T extends/>
+><const T extends/> : <const T>() => any
+>/> : RegExp
+}
+> : any
+
diff --git a/tests/baselines/reference/parseJsxExtends2.errors.txt b/tests/baselines/reference/parseJsxExtends2.errors.txt
new file mode 100644
index 0000000000000..4d4481488055b
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends2.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/index.tsx(2,23): error TS1161: Unterminated regular expression literal.
+tests/cases/compiler/index.tsx(3,1): error TS1005: ',' expected.
+
+
+==== tests/cases/compiler/index.tsx (2 errors) ====
+    export function Foo() {
+        return <T extends/>
+                          
+!!! error TS1161: Unterminated regular expression literal.
+    }
+    ~
+!!! error TS1005: ',' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/parseJsxExtends2.js b/tests/baselines/reference/parseJsxExtends2.js
new file mode 100644
index 0000000000000..3381d90d2e0fd
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends2.js
@@ -0,0 +1,16 @@
+//// [index.tsx]
+export function Foo() {
+    return <T extends/>
+}
+
+
+//// [index.jsx]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.Foo = void 0;
+function Foo() {
+    return function () {
+        return ;
+    };
+}
+exports.Foo = Foo;
diff --git a/tests/baselines/reference/parseJsxExtends2.symbols b/tests/baselines/reference/parseJsxExtends2.symbols
new file mode 100644
index 0000000000000..8953c3f972177
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends2.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/index.tsx ===
+export function Foo() {
+>Foo : Symbol(Foo, Decl(index.tsx, 0, 0))
+
+    return <T extends/>
+>T : Symbol(T, Decl(index.tsx, 1, 12))
+}
+
diff --git a/tests/baselines/reference/parseJsxExtends2.types b/tests/baselines/reference/parseJsxExtends2.types
new file mode 100644
index 0000000000000..2fdbdc2e6e261
--- /dev/null
+++ b/tests/baselines/reference/parseJsxExtends2.types
@@ -0,0 +1,10 @@
+=== tests/cases/compiler/index.tsx ===
+export function Foo() {
+>Foo : () => <T>() => any
+
+    return <T extends/>
+><T extends/> : <T>() => any
+>/> : RegExp
+}
+> : any
+
diff --git a/tests/cases/compiler/parseJsxExtends1.ts b/tests/cases/compiler/parseJsxExtends1.ts
new file mode 100644
index 0000000000000..b0adda26cce53
--- /dev/null
+++ b/tests/cases/compiler/parseJsxExtends1.ts
@@ -0,0 +1,6 @@
+// @jsx: preserve
+// @filename: index.tsx
+
+export function Foo() {
+    return <const T extends/>
+}
diff --git a/tests/cases/compiler/parseJsxExtends2.ts b/tests/cases/compiler/parseJsxExtends2.ts
new file mode 100644
index 0000000000000..3af56ed098f70
--- /dev/null
+++ b/tests/cases/compiler/parseJsxExtends2.ts
@@ -0,0 +1,6 @@
+// @jsx: preserve
+// @filename: index.tsx
+
+export function Foo() {
+    return <T extends/>
+}

From a188cca14c80acf6e860438b93b154f079de4768 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Thu, 26 Jan 2023 19:39:16 -0800
Subject: [PATCH 3/6] Prevent valid JSX from being seen as the start of a
 generic arrow function

---
 src/compiler/parser.ts                           | 16 +++++-----------
 .../reference/parseJsxExtends1.errors.txt        | 13 -------------
 tests/baselines/reference/parseJsxExtends1.js    |  4 +---
 .../baselines/reference/parseJsxExtends1.symbols |  3 ++-
 tests/baselines/reference/parseJsxExtends1.types |  9 +++++----
 .../reference/parseJsxExtends2.errors.txt        | 11 ++++-------
 tests/baselines/reference/parseJsxExtends2.js    |  4 +---
 .../baselines/reference/parseJsxExtends2.symbols |  2 +-
 tests/baselines/reference/parseJsxExtends2.types |  8 ++++----
 9 files changed, 23 insertions(+), 47 deletions(-)
 delete mode 100644 tests/baselines/reference/parseJsxExtends1.errors.txt

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index b448910799401..7474f6328830a 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -5193,7 +5193,7 @@ namespace Parser {
 
             // JSX overrides
             if (languageVariant === LanguageVariant.JSX) {
-                const isArrowFunctionInJsx = lookAhead(() => {
+                return lookAhead(() => {
                     parseOptional(SyntaxKind.ConstKeyword);
                     const third = nextToken();
                     if (third === SyntaxKind.ExtendsKeyword) {
@@ -5201,22 +5201,16 @@ namespace Parser {
                         switch (fourth) {
                             case SyntaxKind.EqualsToken:
                             case SyntaxKind.GreaterThanToken:
-                                return false;
+                                return Tristate.False;
                             default:
-                                return true;
+                                return Tristate.Unknown;
                         }
                     }
                     else if (third === SyntaxKind.CommaToken || third === SyntaxKind.EqualsToken) {
-                        return true;
+                        return Tristate.True;
                     }
-                    return false;
+                    return Tristate.False;
                 });
-
-                if (isArrowFunctionInJsx) {
-                    return Tristate.True;
-                }
-
-                return Tristate.False;
             }
 
             // This *could* be a parenthesized arrow function.
diff --git a/tests/baselines/reference/parseJsxExtends1.errors.txt b/tests/baselines/reference/parseJsxExtends1.errors.txt
deleted file mode 100644
index 617d4927aac5a..0000000000000
--- a/tests/baselines/reference/parseJsxExtends1.errors.txt
+++ /dev/null
@@ -1,13 +0,0 @@
-tests/cases/compiler/index.tsx(2,29): error TS1161: Unterminated regular expression literal.
-tests/cases/compiler/index.tsx(3,1): error TS1005: ',' expected.
-
-
-==== tests/cases/compiler/index.tsx (2 errors) ====
-    export function Foo() {
-        return <const T extends/>
-                                
-!!! error TS1161: Unterminated regular expression literal.
-    }
-    ~
-!!! error TS1005: ',' expected.
-    
\ No newline at end of file
diff --git a/tests/baselines/reference/parseJsxExtends1.js b/tests/baselines/reference/parseJsxExtends1.js
index 542b7f726fc4f..f20b1cdd9df74 100644
--- a/tests/baselines/reference/parseJsxExtends1.js
+++ b/tests/baselines/reference/parseJsxExtends1.js
@@ -9,8 +9,6 @@ export function Foo() {
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.Foo = void 0;
 function Foo() {
-    return function () {
-        return ;
-    };
+    return <const T extends/>;
 }
 exports.Foo = Foo;
diff --git a/tests/baselines/reference/parseJsxExtends1.symbols b/tests/baselines/reference/parseJsxExtends1.symbols
index ef7299a5c9837..5628d6cd505d1 100644
--- a/tests/baselines/reference/parseJsxExtends1.symbols
+++ b/tests/baselines/reference/parseJsxExtends1.symbols
@@ -3,6 +3,7 @@ export function Foo() {
 >Foo : Symbol(Foo, Decl(index.tsx, 0, 0))
 
     return <const T extends/>
->T : Symbol(T, Decl(index.tsx, 1, 12))
+>T : Symbol(T, Decl(index.tsx, 1, 17))
+>extends : Symbol(extends, Decl(index.tsx, 1, 19))
 }
 
diff --git a/tests/baselines/reference/parseJsxExtends1.types b/tests/baselines/reference/parseJsxExtends1.types
index 03425efb2db40..e9c75a9635580 100644
--- a/tests/baselines/reference/parseJsxExtends1.types
+++ b/tests/baselines/reference/parseJsxExtends1.types
@@ -1,10 +1,11 @@
 === tests/cases/compiler/index.tsx ===
 export function Foo() {
->Foo : () => <const T>() => any
+>Foo : () => any
 
     return <const T extends/>
-><const T extends/> : <const T>() => any
->/> : RegExp
+><const T extends/> : error
+>const : any
+>T : true
+>extends : true
 }
-> : any
 
diff --git a/tests/baselines/reference/parseJsxExtends2.errors.txt b/tests/baselines/reference/parseJsxExtends2.errors.txt
index 4d4481488055b..09b7ebb632f8b 100644
--- a/tests/baselines/reference/parseJsxExtends2.errors.txt
+++ b/tests/baselines/reference/parseJsxExtends2.errors.txt
@@ -1,13 +1,10 @@
-tests/cases/compiler/index.tsx(2,23): error TS1161: Unterminated regular expression literal.
-tests/cases/compiler/index.tsx(3,1): error TS1005: ',' expected.
+tests/cases/compiler/index.tsx(2,13): error TS2304: Cannot find name 'T'.
 
 
-==== tests/cases/compiler/index.tsx (2 errors) ====
+==== tests/cases/compiler/index.tsx (1 errors) ====
     export function Foo() {
         return <T extends/>
-                          
-!!! error TS1161: Unterminated regular expression literal.
+                ~
+!!! error TS2304: Cannot find name 'T'.
     }
-    ~
-!!! error TS1005: ',' expected.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parseJsxExtends2.js b/tests/baselines/reference/parseJsxExtends2.js
index 3381d90d2e0fd..5f5f019bd7144 100644
--- a/tests/baselines/reference/parseJsxExtends2.js
+++ b/tests/baselines/reference/parseJsxExtends2.js
@@ -9,8 +9,6 @@ export function Foo() {
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.Foo = void 0;
 function Foo() {
-    return function () {
-        return ;
-    };
+    return <T extends/>;
 }
 exports.Foo = Foo;
diff --git a/tests/baselines/reference/parseJsxExtends2.symbols b/tests/baselines/reference/parseJsxExtends2.symbols
index 8953c3f972177..79827f185d4b8 100644
--- a/tests/baselines/reference/parseJsxExtends2.symbols
+++ b/tests/baselines/reference/parseJsxExtends2.symbols
@@ -3,6 +3,6 @@ export function Foo() {
 >Foo : Symbol(Foo, Decl(index.tsx, 0, 0))
 
     return <T extends/>
->T : Symbol(T, Decl(index.tsx, 1, 12))
+>extends : Symbol(extends, Decl(index.tsx, 1, 13))
 }
 
diff --git a/tests/baselines/reference/parseJsxExtends2.types b/tests/baselines/reference/parseJsxExtends2.types
index 2fdbdc2e6e261..33ae73c3a177d 100644
--- a/tests/baselines/reference/parseJsxExtends2.types
+++ b/tests/baselines/reference/parseJsxExtends2.types
@@ -1,10 +1,10 @@
 === tests/cases/compiler/index.tsx ===
 export function Foo() {
->Foo : () => <T>() => any
+>Foo : () => any
 
     return <T extends/>
-><T extends/> : <T>() => any
->/> : RegExp
+><T extends/> : any
+>T : any
+>extends : true
 }
-> : any
 

From c705d8cd6ca5cff62b5cd73bca85c698a4cb21ff Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Thu, 26 Jan 2023 20:06:26 -0800
Subject: [PATCH 4/6] Make test clearer

---
 tests/baselines/reference/parseJsxExtends1.js         |  8 ++++++--
 tests/baselines/reference/parseJsxExtends1.symbols    | 10 +++++++---
 tests/baselines/reference/parseJsxExtends1.types      |  4 ++++
 tests/baselines/reference/parseJsxExtends2.errors.txt |  5 ++++-
 tests/baselines/reference/parseJsxExtends2.js         |  8 ++++++--
 tests/baselines/reference/parseJsxExtends2.symbols    |  8 ++++++--
 tests/baselines/reference/parseJsxExtends2.types      |  4 ++++
 tests/cases/compiler/parseJsxExtends1.ts              |  5 ++++-
 tests/cases/compiler/parseJsxExtends2.ts              |  5 ++++-
 9 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/tests/baselines/reference/parseJsxExtends1.js b/tests/baselines/reference/parseJsxExtends1.js
index f20b1cdd9df74..893228c3f6855 100644
--- a/tests/baselines/reference/parseJsxExtends1.js
+++ b/tests/baselines/reference/parseJsxExtends1.js
@@ -1,14 +1,18 @@
 //// [index.tsx]
+declare const React: any;
+
 export function Foo() {
+    // No error; "const" is lowercase and therefore intrinsic.
     return <const T extends/>
 }
 
 
-//// [index.jsx]
+//// [index.js]
 "use strict";
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.Foo = void 0;
 function Foo() {
-    return <const T extends/>;
+    // No error; "const" is lowercase and therefore intrinsic.
+    return React.createElement("const", { T: true, extends: true });
 }
 exports.Foo = Foo;
diff --git a/tests/baselines/reference/parseJsxExtends1.symbols b/tests/baselines/reference/parseJsxExtends1.symbols
index 5628d6cd505d1..7b4981044b6b3 100644
--- a/tests/baselines/reference/parseJsxExtends1.symbols
+++ b/tests/baselines/reference/parseJsxExtends1.symbols
@@ -1,9 +1,13 @@
 === tests/cases/compiler/index.tsx ===
+declare const React: any;
+>React : Symbol(React, Decl(index.tsx, 0, 13))
+
 export function Foo() {
->Foo : Symbol(Foo, Decl(index.tsx, 0, 0))
+>Foo : Symbol(Foo, Decl(index.tsx, 0, 25))
 
+    // No error; "const" is lowercase and therefore intrinsic.
     return <const T extends/>
->T : Symbol(T, Decl(index.tsx, 1, 17))
->extends : Symbol(extends, Decl(index.tsx, 1, 19))
+>T : Symbol(T, Decl(index.tsx, 4, 17))
+>extends : Symbol(extends, Decl(index.tsx, 4, 19))
 }
 
diff --git a/tests/baselines/reference/parseJsxExtends1.types b/tests/baselines/reference/parseJsxExtends1.types
index e9c75a9635580..5e605aa1e2515 100644
--- a/tests/baselines/reference/parseJsxExtends1.types
+++ b/tests/baselines/reference/parseJsxExtends1.types
@@ -1,7 +1,11 @@
 === tests/cases/compiler/index.tsx ===
+declare const React: any;
+>React : any
+
 export function Foo() {
 >Foo : () => any
 
+    // No error; "const" is lowercase and therefore intrinsic.
     return <const T extends/>
 ><const T extends/> : error
 >const : any
diff --git a/tests/baselines/reference/parseJsxExtends2.errors.txt b/tests/baselines/reference/parseJsxExtends2.errors.txt
index 09b7ebb632f8b..d482f0277abe5 100644
--- a/tests/baselines/reference/parseJsxExtends2.errors.txt
+++ b/tests/baselines/reference/parseJsxExtends2.errors.txt
@@ -1,8 +1,11 @@
-tests/cases/compiler/index.tsx(2,13): error TS2304: Cannot find name 'T'.
+tests/cases/compiler/index.tsx(5,13): error TS2304: Cannot find name 'T'.
 
 
 ==== tests/cases/compiler/index.tsx (1 errors) ====
+    declare const React: any;
+    
     export function Foo() {
+        // Error: T is not declared.
         return <T extends/>
                 ~
 !!! error TS2304: Cannot find name 'T'.
diff --git a/tests/baselines/reference/parseJsxExtends2.js b/tests/baselines/reference/parseJsxExtends2.js
index 5f5f019bd7144..7a09169319c6c 100644
--- a/tests/baselines/reference/parseJsxExtends2.js
+++ b/tests/baselines/reference/parseJsxExtends2.js
@@ -1,14 +1,18 @@
 //// [index.tsx]
+declare const React: any;
+
 export function Foo() {
+    // Error: T is not declared.
     return <T extends/>
 }
 
 
-//// [index.jsx]
+//// [index.js]
 "use strict";
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.Foo = void 0;
 function Foo() {
-    return <T extends/>;
+    // Error: T is not declared.
+    return React.createElement(T, { extends: true });
 }
 exports.Foo = Foo;
diff --git a/tests/baselines/reference/parseJsxExtends2.symbols b/tests/baselines/reference/parseJsxExtends2.symbols
index 79827f185d4b8..b222fb8d35cc8 100644
--- a/tests/baselines/reference/parseJsxExtends2.symbols
+++ b/tests/baselines/reference/parseJsxExtends2.symbols
@@ -1,8 +1,12 @@
 === tests/cases/compiler/index.tsx ===
+declare const React: any;
+>React : Symbol(React, Decl(index.tsx, 0, 13))
+
 export function Foo() {
->Foo : Symbol(Foo, Decl(index.tsx, 0, 0))
+>Foo : Symbol(Foo, Decl(index.tsx, 0, 25))
 
+    // Error: T is not declared.
     return <T extends/>
->extends : Symbol(extends, Decl(index.tsx, 1, 13))
+>extends : Symbol(extends, Decl(index.tsx, 4, 13))
 }
 
diff --git a/tests/baselines/reference/parseJsxExtends2.types b/tests/baselines/reference/parseJsxExtends2.types
index 33ae73c3a177d..b9dcb4f5958d0 100644
--- a/tests/baselines/reference/parseJsxExtends2.types
+++ b/tests/baselines/reference/parseJsxExtends2.types
@@ -1,7 +1,11 @@
 === tests/cases/compiler/index.tsx ===
+declare const React: any;
+>React : any
+
 export function Foo() {
 >Foo : () => any
 
+    // Error: T is not declared.
     return <T extends/>
 ><T extends/> : any
 >T : any
diff --git a/tests/cases/compiler/parseJsxExtends1.ts b/tests/cases/compiler/parseJsxExtends1.ts
index b0adda26cce53..7dbf396d6efc8 100644
--- a/tests/cases/compiler/parseJsxExtends1.ts
+++ b/tests/cases/compiler/parseJsxExtends1.ts
@@ -1,6 +1,9 @@
-// @jsx: preserve
+// @jsx: react
 // @filename: index.tsx
 
+declare const React: any;
+
 export function Foo() {
+    // No error; "const" is lowercase and therefore intrinsic.
     return <const T extends/>
 }
diff --git a/tests/cases/compiler/parseJsxExtends2.ts b/tests/cases/compiler/parseJsxExtends2.ts
index 3af56ed098f70..10309c2b6dc53 100644
--- a/tests/cases/compiler/parseJsxExtends2.ts
+++ b/tests/cases/compiler/parseJsxExtends2.ts
@@ -1,6 +1,9 @@
-// @jsx: preserve
+// @jsx: react
 // @filename: index.tsx
 
+declare const React: any;
+
 export function Foo() {
+    // Error: T is not declared.
     return <T extends/>
 }

From 431668be0262f01ab28d987ae369d5017b6bd43c Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Fri, 27 Jan 2023 10:07:16 -0800
Subject: [PATCH 5/6] PR feedback

---
 src/compiler/parser.ts | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 7474f6328830a..766aac9e595b8 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -5193,7 +5193,7 @@ namespace Parser {
 
             // JSX overrides
             if (languageVariant === LanguageVariant.JSX) {
-                return lookAhead(() => {
+                const isArrowFunctionInJsx = lookAhead(() => {
                     parseOptional(SyntaxKind.ConstKeyword);
                     const third = nextToken();
                     if (third === SyntaxKind.ExtendsKeyword) {
@@ -5201,16 +5201,23 @@ namespace Parser {
                         switch (fourth) {
                             case SyntaxKind.EqualsToken:
                             case SyntaxKind.GreaterThanToken:
-                                return Tristate.False;
+                            case SyntaxKind.SlashToken:
+                                return false;
                             default:
-                                return Tristate.Unknown;
+                                return true;
                         }
                     }
                     else if (third === SyntaxKind.CommaToken || third === SyntaxKind.EqualsToken) {
-                        return Tristate.True;
+                        return true;
                     }
-                    return Tristate.False;
+                    return false;
                 });
+
+                if (isArrowFunctionInJsx) {
+                    return Tristate.True;
+                }
+
+                return Tristate.False;
             }
 
             // This *could* be a parenthesized arrow function.

From 7c43af896858b07147c03c094d8a8584f6c00c5f Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Fri, 27 Jan 2023 10:41:26 -0800
Subject: [PATCH 6/6] Fix rangeOfTypeParameters to not exceed file length

---
 src/compiler/utilities.ts                          | 2 +-
 tests/cases/fourslash/jsxElementExtendsNoCrash3.ts | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/jsxElementExtendsNoCrash3.ts

diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 57c7bf9aa8329..dd340dbfe8d22 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -9079,7 +9079,7 @@ export function rangeOfNode(node: Node): TextRange {
 export function rangeOfTypeParameters(sourceFile: SourceFile, typeParameters: NodeArray<TypeParameterDeclaration>): TextRange {
     // Include the `<>`
     const pos = typeParameters.pos - 1;
-    const end = skipTrivia(sourceFile.text, typeParameters.end) + 1;
+    const end = Math.min(sourceFile.text.length, skipTrivia(sourceFile.text, typeParameters.end) + 1);
     return { pos, end };
 }
 
diff --git a/tests/cases/fourslash/jsxElementExtendsNoCrash3.ts b/tests/cases/fourslash/jsxElementExtendsNoCrash3.ts
new file mode 100644
index 0000000000000..c4b85cb423046
--- /dev/null
+++ b/tests/cases/fourslash/jsxElementExtendsNoCrash3.ts
@@ -0,0 +1,6 @@
+/// <reference path="fourslash.ts" />
+
+// @filename: index.tsx
+//// <T extends /=>
+
+verify.getSuggestionDiagnostics([]);