From 562eb0ae15b24f5f88d785d865df30f1da39afb1 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 11:03:42 -0700
Subject: [PATCH 1/7] Add test case

---
 .../parserArrowFunctionExpression15.errors.txt     | 14 ++++++++++++++
 .../reference/parserArrowFunctionExpression15.js   |  7 +++++++
 .../parserArrowFunctionExpression15.symbols        |  4 ++++
 .../parserArrowFunctionExpression15.types          | 11 +++++++++++
 .../parserArrowFunctionExpression16.errors.txt     | 14 ++++++++++++++
 .../reference/parserArrowFunctionExpression16.js   |  7 +++++++
 .../parserArrowFunctionExpression16.symbols        |  4 ++++
 .../parserArrowFunctionExpression16.types          | 14 ++++++++++++++
 .../parserArrowFunctionExpression15.ts             |  1 +
 .../parserArrowFunctionExpression16.ts             |  1 +
 10 files changed, 77 insertions(+)
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression15.js
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression15.symbols
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression15.types
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression16.js
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression16.symbols
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression16.types
 create mode 100644 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts
 create mode 100644 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts

diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
new file mode 100644
index 0000000000000..60def8ca15fa6
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,10): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,28): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,34): error TS1005: ';' expected.
+
+
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts (3 errors) ====
+    false ? (param): string => param : null
+             ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                               ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                     ~
+!!! error TS1005: ';' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.js b/tests/baselines/reference/parserArrowFunctionExpression15.js
new file mode 100644
index 0000000000000..047b09c6ddec0
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.js
@@ -0,0 +1,7 @@
+//// [parserArrowFunctionExpression15.ts]
+false ? (param): string => param : null
+
+
+//// [parserArrowFunctionExpression15.js]
+false ? (param) : function (string) { return param; };
+null;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.symbols b/tests/baselines/reference/parserArrowFunctionExpression15.symbols
new file mode 100644
index 0000000000000..7750b8d43be97
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.symbols
@@ -0,0 +1,4 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
+false ? (param): string => param : null
+>string : Symbol(string, Decl(parserArrowFunctionExpression15.ts, 0, 16))
+
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.types b/tests/baselines/reference/parserArrowFunctionExpression15.types
new file mode 100644
index 0000000000000..ec808c729eece
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.types
@@ -0,0 +1,11 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
+false ? (param): string => param : null
+>false ? (param): string => param : any
+>false : false
+>(param) : any
+>param : any
+>string => param : (string: any) => any
+>string : any
+>param : any
+>null : null
+
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
new file mode 100644
index 0000000000000..740144391e298
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,17): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,35): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,48): error TS1005: ';' expected.
+
+
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts (3 errors) ====
+    true ? false ? (param): string => param : null : null
+                    ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                      ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                                   ~
+!!! error TS1005: ';' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.js b/tests/baselines/reference/parserArrowFunctionExpression16.js
new file mode 100644
index 0000000000000..a2b2fff3aad85
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.js
@@ -0,0 +1,7 @@
+//// [parserArrowFunctionExpression16.ts]
+true ? false ? (param): string => param : null : null
+
+
+//// [parserArrowFunctionExpression16.js]
+true ? false ? (param) : function (string) { return param; } : null;
+null;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.symbols b/tests/baselines/reference/parserArrowFunctionExpression16.symbols
new file mode 100644
index 0000000000000..684b74408ccd5
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.symbols
@@ -0,0 +1,4 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
+true ? false ? (param): string => param : null : null
+>string : Symbol(string, Decl(parserArrowFunctionExpression16.ts, 0, 23))
+
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.types b/tests/baselines/reference/parserArrowFunctionExpression16.types
new file mode 100644
index 0000000000000..dbe5cc2e81733
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.types
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
+true ? false ? (param): string => param : null : null
+>true ? false ? (param): string => param : null : any
+>true : true
+>false ? (param): string => param : any
+>false : false
+>(param) : any
+>param : any
+>string => param : (string: any) => any
+>string : any
+>param : any
+>null : null
+>null : null
+
diff --git a/tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts b/tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts
new file mode 100644
index 0000000000000..3348d24bfebe4
--- /dev/null
+++ b/tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts
@@ -0,0 +1 @@
+false ? (param): string => param : null
diff --git a/tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts b/tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts
new file mode 100644
index 0000000000000..9a19bfdb6cfc1
--- /dev/null
+++ b/tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts
@@ -0,0 +1 @@
+true ? false ? (param): string => param : null : null

From d4d606d8e554a4546e0a6836e84408c3705937ac Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 13:57:09 -0700
Subject: [PATCH 2/7] Allow return type in conditional if body is followed by a
 colon

---
 src/compiler/parser.ts                           | 16 +++++++++++++---
 .../parserArrowFunctionExpression10.errors.txt   | 11 ++++-------
 .../reference/parserArrowFunctionExpression10.js |  3 +--
 .../parserArrowFunctionExpression10.symbols      |  3 ++-
 .../parserArrowFunctionExpression10.types        |  6 ++----
 .../parserArrowFunctionExpression12.errors.txt   | 11 ++++++++++-
 .../reference/parserArrowFunctionExpression12.js |  4 +++-
 .../parserArrowFunctionExpression12.symbols      |  1 -
 .../parserArrowFunctionExpression12.types        |  5 +++--
 .../parserArrowFunctionExpression15.errors.txt   | 14 --------------
 .../reference/parserArrowFunctionExpression15.js |  3 +--
 .../parserArrowFunctionExpression15.symbols      |  3 ++-
 .../parserArrowFunctionExpression15.types        |  6 ++----
 .../parserArrowFunctionExpression16.errors.txt   | 14 --------------
 .../reference/parserArrowFunctionExpression16.js |  3 +--
 .../parserArrowFunctionExpression16.symbols      |  3 ++-
 .../parserArrowFunctionExpression16.types        |  8 +++-----
 17 files changed, 49 insertions(+), 65 deletions(-)
 delete mode 100644 tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
 delete mode 100644 tests/baselines/reference/parserArrowFunctionExpression16.errors.txt

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index e57a3fa98f390..baaef1c654f9d 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4709,9 +4709,9 @@ namespace ts {
             //     a() ? (b: number, c?: string): void => d() : e
             // is determined by isParenthesizedArrowFunctionExpression to unambiguously
             // be an arrow expression, so we allow a return type.
-            if (disallowReturnTypeInArrowFunction && token() === SyntaxKind.ColonToken) {
-                return undefined;
-            }
+            // if (disallowReturnTypeInArrowFunction && token() === SyntaxKind.ColonToken) {
+            //     return undefined;
+            // }
 
             const type = parseReturnType(SyntaxKind.ColonToken, /*isType*/ false);
             if (type && !allowAmbiguity && typeHasArrowFunctionBlockingParseError(type)) {
@@ -4748,6 +4748,16 @@ namespace ts {
                 ? parseArrowFunctionExpressionBody(some(modifiers, isAsyncModifier), disallowReturnTypeInArrowFunction)
                 : parseIdentifier();
 
+            if (disallowReturnTypeInArrowFunction) {
+                // If we are currently parsing a conditional expression, and were able to parse
+                // a return type before the body, and there's another colon after the body, allow
+                // parsing of this arrow function so that the following colon terminates the
+                // true side of the conditional.
+                if (!(type && token() === SyntaxKind.ColonToken)) {
+                    return undefined;
+                }
+            }
+
             const node = factory.createArrowFunction(modifiers, typeParameters, parameters, type, equalsGreaterThanToken, body);
             return withJSDoc(finishNode(node, pos), hasJSDoc);
         }
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt
index 43cf9de267b85..0ee29b021a1ef 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt
@@ -1,20 +1,17 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,1): error TS2304: Cannot find name 'a'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,6): error TS2304: Cannot find name 'b'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,11): error TS2304: Cannot find name 'c'.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,17): error TS2304: Cannot find name 'd'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,20): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,27): error TS2304: Cannot find name 'f'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts (5 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts (4 errors) ====
     a ? (b) : c => (d) : e => f
     ~
 !!! error TS2304: Cannot find name 'a'.
-         ~
-!!! error TS2304: Cannot find name 'b'.
+              ~
+!!! error TS2304: Cannot find name 'c'.
                     ~
 !!! error TS2304: Cannot find name 'd'.
-                       ~
-!!! error TS1005: ';' expected.
                               ~
 !!! error TS2304: Cannot find name 'f'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.js b/tests/baselines/reference/parserArrowFunctionExpression10.js
index 86e1e61bb0716..7681332637b4e 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.js
@@ -3,5 +3,4 @@ a ? (b) : c => (d) : e => f
 
 
 //// [parserArrowFunctionExpression10.js]
-a ? (b) : function (c) { return (d); };
-(function (e) { return f; });
+a ? function (b) { return (d); } : function (e) { return f; };
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.symbols b/tests/baselines/reference/parserArrowFunctionExpression10.symbols
index f30f0b3e3ca49..df391a0be345d 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.symbols
@@ -1,5 +1,6 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts ===
 a ? (b) : c => (d) : e => f
->c : Symbol(c, Decl(parserArrowFunctionExpression10.ts, 0, 9))
+>b : Symbol(b, Decl(parserArrowFunctionExpression10.ts, 0, 5))
+>c : Symbol(c)
 >e : Symbol(e, Decl(parserArrowFunctionExpression10.ts, 0, 20))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.types b/tests/baselines/reference/parserArrowFunctionExpression10.types
index 8ec7d69c29559..e4149fe4cbb5c 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.types
@@ -1,11 +1,9 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts ===
 a ? (b) : c => (d) : e => f
->a ? (b) : c => (d) : any
+>a ? (b) : c => (d) : e => f : (b: any) => c
 >a : any
->(b) : any
+>(b) : c => (d) : (b: any) => c
 >b : any
->c => (d) : (c: any) => any
->c : any
 >(d) : any
 >d : any
 >e => f : (e: any) => any
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt
index c6cfd8f9ce855..bc6625a0e5a99 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt
@@ -1,14 +1,23 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,1): error TS2304: Cannot find name 'a'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,6): error TS2304: Cannot find name 'b'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,9): error TS1005: ':' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,13): error TS2304: Cannot find name 'c'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,15): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,22): error TS2304: Cannot find name 'e'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts (3 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts (6 errors) ====
     a ? (b) => (c): d => e
     ~
 !!! error TS2304: Cannot find name 'a'.
+         ~
+!!! error TS2304: Cannot find name 'b'.
+            ~~
+!!! error TS1005: ':' expected.
                 ~
 !!! error TS2304: Cannot find name 'c'.
+                  ~
+!!! error TS1005: ';' expected.
                          ~
 !!! error TS2304: Cannot find name 'e'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.js b/tests/baselines/reference/parserArrowFunctionExpression12.js
index dbee37a2660cb..416b1aa1a6270 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.js
@@ -3,4 +3,6 @@ a ? (b) => (c): d => e
 
 
 //// [parserArrowFunctionExpression12.js]
-a ? function (b) { return (c); } : function (d) { return e; };
+a ? (b) : ;
+(c);
+(function (d) { return e; });
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.symbols b/tests/baselines/reference/parserArrowFunctionExpression12.symbols
index 3a67717232041..c72b2d870c8e5 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.symbols
@@ -1,5 +1,4 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts ===
 a ? (b) => (c): d => e
->b : Symbol(b, Decl(parserArrowFunctionExpression12.ts, 0, 5))
 >d : Symbol(d, Decl(parserArrowFunctionExpression12.ts, 0, 15))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.types b/tests/baselines/reference/parserArrowFunctionExpression12.types
index b833ae305a8b1..8ebbf59b7a0a5 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.types
@@ -1,9 +1,10 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts ===
 a ? (b) => (c): d => e
->a ? (b) => (c): d => e : (b: any) => any
+>a ? (b) : any
 >a : any
->(b) => (c) : (b: any) => any
+>(b) : any
 >b : any
+> : any
 >(c) : any
 >c : any
 >d => e : (d: any) => any
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
deleted file mode 100644
index 60def8ca15fa6..0000000000000
--- a/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
+++ /dev/null
@@ -1,14 +0,0 @@
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,10): error TS2304: Cannot find name 'param'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,28): error TS2304: Cannot find name 'param'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,34): error TS1005: ';' expected.
-
-
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts (3 errors) ====
-    false ? (param): string => param : null
-             ~~~~~
-!!! error TS2304: Cannot find name 'param'.
-                               ~~~~~
-!!! error TS2304: Cannot find name 'param'.
-                                     ~
-!!! error TS1005: ';' expected.
-    
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.js b/tests/baselines/reference/parserArrowFunctionExpression15.js
index 047b09c6ddec0..a18efc84f0975 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression15.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.js
@@ -3,5 +3,4 @@ false ? (param): string => param : null
 
 
 //// [parserArrowFunctionExpression15.js]
-false ? (param) : function (string) { return param; };
-null;
+false ? function (param) { return param; } : null;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.symbols b/tests/baselines/reference/parserArrowFunctionExpression15.symbols
index 7750b8d43be97..7cb354c7dc912 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression15.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.symbols
@@ -1,4 +1,5 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
 false ? (param): string => param : null
->string : Symbol(string, Decl(parserArrowFunctionExpression15.ts, 0, 16))
+>param : Symbol(param, Decl(parserArrowFunctionExpression15.ts, 0, 9))
+>param : Symbol(param, Decl(parserArrowFunctionExpression15.ts, 0, 9))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.types b/tests/baselines/reference/parserArrowFunctionExpression15.types
index ec808c729eece..4640763862112 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression15.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.types
@@ -1,11 +1,9 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
 false ? (param): string => param : null
->false ? (param): string => param : any
+>false ? (param): string => param : null : (param: any) => string
 >false : false
->(param) : any
+>(param): string => param : (param: any) => string
 >param : any
->string => param : (string: any) => any
->string : any
 >param : any
 >null : null
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
deleted file mode 100644
index 740144391e298..0000000000000
--- a/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
+++ /dev/null
@@ -1,14 +0,0 @@
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,17): error TS2304: Cannot find name 'param'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,35): error TS2304: Cannot find name 'param'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,48): error TS1005: ';' expected.
-
-
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts (3 errors) ====
-    true ? false ? (param): string => param : null : null
-                    ~~~~~
-!!! error TS2304: Cannot find name 'param'.
-                                      ~~~~~
-!!! error TS2304: Cannot find name 'param'.
-                                                   ~
-!!! error TS1005: ';' expected.
-    
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.js b/tests/baselines/reference/parserArrowFunctionExpression16.js
index a2b2fff3aad85..8d0404c91c853 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression16.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.js
@@ -3,5 +3,4 @@ true ? false ? (param): string => param : null : null
 
 
 //// [parserArrowFunctionExpression16.js]
-true ? false ? (param) : function (string) { return param; } : null;
-null;
+true ? false ? function (param) { return param; } : null : null;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.symbols b/tests/baselines/reference/parserArrowFunctionExpression16.symbols
index 684b74408ccd5..f2a4ff04df134 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression16.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.symbols
@@ -1,4 +1,5 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
 true ? false ? (param): string => param : null : null
->string : Symbol(string, Decl(parserArrowFunctionExpression16.ts, 0, 23))
+>param : Symbol(param, Decl(parserArrowFunctionExpression16.ts, 0, 16))
+>param : Symbol(param, Decl(parserArrowFunctionExpression16.ts, 0, 16))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.types b/tests/baselines/reference/parserArrowFunctionExpression16.types
index dbe5cc2e81733..fffd623adac0d 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression16.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.types
@@ -1,13 +1,11 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
 true ? false ? (param): string => param : null : null
->true ? false ? (param): string => param : null : any
+>true ? false ? (param): string => param : null : null : (param: any) => string
 >true : true
->false ? (param): string => param : any
+>false ? (param): string => param : null : (param: any) => string
 >false : false
->(param) : any
+>(param): string => param : (param: any) => string
 >param : any
->string => param : (string: any) => any
->string : any
 >param : any
 >null : null
 >null : null

From 61e987b41404a7f7179f70c79ef688d98069e997 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 14:00:42 -0700
Subject: [PATCH 3/7] Move comment

---
 src/compiler/parser.ts | 41 +++++++++++++++++++----------------------
 1 file changed, 19 insertions(+), 22 deletions(-)

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index baaef1c654f9d..7e69904f0a49a 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4695,24 +4695,6 @@ namespace ts {
                 }
             }
 
-            // Given:
-            //     x ? y => ({ y }) : z => ({ z })
-            // We try to parse the body of the first arrow function by looking at:
-            //     ({ y }) : z => ({ z })
-            // This is a valid arrow function with "z" as the return type.
-            //
-            // But, if we're in the true side of a conditional expression, this colon
-            // terminates the expression, so we cannot allow a return type if we aren't
-            // certain whether or not the preceding text was parsed as a parameter list.
-            //
-            // For example,
-            //     a() ? (b: number, c?: string): void => d() : e
-            // is determined by isParenthesizedArrowFunctionExpression to unambiguously
-            // be an arrow expression, so we allow a return type.
-            // if (disallowReturnTypeInArrowFunction && token() === SyntaxKind.ColonToken) {
-            //     return undefined;
-            // }
-
             const type = parseReturnType(SyntaxKind.ColonToken, /*isType*/ false);
             if (type && !allowAmbiguity && typeHasArrowFunctionBlockingParseError(type)) {
                 return undefined;
@@ -4748,11 +4730,26 @@ namespace ts {
                 ? parseArrowFunctionExpressionBody(some(modifiers, isAsyncModifier), disallowReturnTypeInArrowFunction)
                 : parseIdentifier();
 
+            // Given:
+            //     x ? y => ({ y }) : z => ({ z })
+            // We try to parse the body of the first arrow function by looking at:
+            //     ({ y }) : z => ({ z })
+            // This is a valid arrow function with "z" as the return type.
+            //
+            // But, if we're in the true side of a conditional expression, this colon
+            // terminates the expression, so we cannot allow a return type if we aren't
+            // certain whether or not the preceding text was parsed as a parameter list.
+            //
+            // For example,
+            //     a() ? (b: number, c?: string): void => d() : e
+            // is determined by isParenthesizedArrowFunctionExpression to unambiguously
+            // be an arrow expression, so we allow a return type.
             if (disallowReturnTypeInArrowFunction) {
-                // If we are currently parsing a conditional expression, and were able to parse
-                // a return type before the body, and there's another colon after the body, allow
-                // parsing of this arrow function so that the following colon terminates the
-                // true side of the conditional.
+                // However, if the arrow function we were able to parse is followed by another colon
+                // as in:
+                //     a ? (x): string => x : null
+                // Then allow the arrow function, and treat the second colon as terminating
+                // the conditional expression.
                 if (!(type && token() === SyntaxKind.ColonToken)) {
                     return undefined;
                 }

From 3b2ec35bb637c4bac630e46534498275423989b0 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 14:31:47 -0700
Subject: [PATCH 4/7] Remember colon from earlier

---
 src/compiler/parser.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 7e69904f0a49a..f055c326b0a33 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4695,6 +4695,7 @@ namespace ts {
                 }
             }
 
+            const hasReturnColon = token() === SyntaxKind.ColonToken;
             const type = parseReturnType(SyntaxKind.ColonToken, /*isType*/ false);
             if (type && !allowAmbiguity && typeHasArrowFunctionBlockingParseError(type)) {
                 return undefined;
@@ -4744,13 +4745,13 @@ namespace ts {
             //     a() ? (b: number, c?: string): void => d() : e
             // is determined by isParenthesizedArrowFunctionExpression to unambiguously
             // be an arrow expression, so we allow a return type.
-            if (disallowReturnTypeInArrowFunction) {
+            if (disallowReturnTypeInArrowFunction && hasReturnColon) {
                 // However, if the arrow function we were able to parse is followed by another colon
                 // as in:
                 //     a ? (x): string => x : null
                 // Then allow the arrow function, and treat the second colon as terminating
                 // the conditional expression.
-                if (!(type && token() === SyntaxKind.ColonToken)) {
+                if (token() !== SyntaxKind.ColonToken) {
                     return undefined;
                 }
             }

From 23987628a368823bfe958f8ab09451320b088872 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 14:32:23 -0700
Subject: [PATCH 5/7] Revert 12

---
 .../parserArrowFunctionExpression12.errors.txt        | 11 +----------
 .../reference/parserArrowFunctionExpression12.js      |  4 +---
 .../reference/parserArrowFunctionExpression12.symbols |  1 +
 .../reference/parserArrowFunctionExpression12.types   |  5 ++---
 4 files changed, 5 insertions(+), 16 deletions(-)

diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt
index bc6625a0e5a99..c6cfd8f9ce855 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.errors.txt
@@ -1,23 +1,14 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,1): error TS2304: Cannot find name 'a'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,6): error TS2304: Cannot find name 'b'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,9): error TS1005: ':' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,13): error TS2304: Cannot find name 'c'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,15): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts(1,22): error TS2304: Cannot find name 'e'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts (6 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts (3 errors) ====
     a ? (b) => (c): d => e
     ~
 !!! error TS2304: Cannot find name 'a'.
-         ~
-!!! error TS2304: Cannot find name 'b'.
-            ~~
-!!! error TS1005: ':' expected.
                 ~
 !!! error TS2304: Cannot find name 'c'.
-                  ~
-!!! error TS1005: ';' expected.
                          ~
 !!! error TS2304: Cannot find name 'e'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.js b/tests/baselines/reference/parserArrowFunctionExpression12.js
index 416b1aa1a6270..dbee37a2660cb 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.js
@@ -3,6 +3,4 @@ a ? (b) => (c): d => e
 
 
 //// [parserArrowFunctionExpression12.js]
-a ? (b) : ;
-(c);
-(function (d) { return e; });
+a ? function (b) { return (c); } : function (d) { return e; };
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.symbols b/tests/baselines/reference/parserArrowFunctionExpression12.symbols
index c72b2d870c8e5..3a67717232041 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.symbols
@@ -1,4 +1,5 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts ===
 a ? (b) => (c): d => e
+>b : Symbol(b, Decl(parserArrowFunctionExpression12.ts, 0, 5))
 >d : Symbol(d, Decl(parserArrowFunctionExpression12.ts, 0, 15))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression12.types b/tests/baselines/reference/parserArrowFunctionExpression12.types
index 8ebbf59b7a0a5..b833ae305a8b1 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression12.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression12.types
@@ -1,10 +1,9 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression12.ts ===
 a ? (b) => (c): d => e
->a ? (b) : any
+>a ? (b) => (c): d => e : (b: any) => any
 >a : any
->(b) : any
+>(b) => (c) : (b: any) => any
 >b : any
-> : any
 >(c) : any
 >c : any
 >d => e : (d: any) => any

From f5ecb512d53cf938854a6ec8c61534f69b37d15b Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 16:01:25 -0700
Subject: [PATCH 6/7] Make strict

---
 src/compiler/parser.ts                        | 56 ++++++++-----------
 ...parserArrowFunctionExpression10.errors.txt | 11 ++--
 .../parserArrowFunctionExpression10.js        |  3 +-
 .../parserArrowFunctionExpression10.symbols   |  3 +-
 .../parserArrowFunctionExpression10.types     |  6 +-
 ...parserArrowFunctionExpression13.errors.txt |  8 ++-
 .../parserArrowFunctionExpression13.js        |  3 +-
 .../parserArrowFunctionExpression13.symbols   |  4 +-
 .../parserArrowFunctionExpression13.types     |  7 ++-
 ...parserArrowFunctionExpression14.errors.txt | 11 +++-
 .../parserArrowFunctionExpression14.js        |  4 +-
 .../parserArrowFunctionExpression14.symbols   |  5 +-
 .../parserArrowFunctionExpression14.types     |  8 +--
 ...parserArrowFunctionExpression15.errors.txt | 14 +++++
 .../parserArrowFunctionExpression15.js        |  3 +-
 .../parserArrowFunctionExpression15.symbols   |  3 +-
 .../parserArrowFunctionExpression15.types     |  6 +-
 ...parserArrowFunctionExpression16.errors.txt | 14 +++++
 .../parserArrowFunctionExpression16.js        |  3 +-
 .../parserArrowFunctionExpression16.symbols   |  3 +-
 .../parserArrowFunctionExpression16.types     |  8 ++-
 21 files changed, 116 insertions(+), 67 deletions(-)
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
 create mode 100644 tests/baselines/reference/parserArrowFunctionExpression16.errors.txt

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index f055c326b0a33..20cacf711592e 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4452,7 +4452,7 @@ namespace ts {
         }
 
         function tryParseParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction: boolean): Expression | undefined {
-            const triState = isParenthesizedArrowFunctionExpression();
+            const triState = isParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction);
             if (triState === Tristate.False) {
                 // It's definitely not a parenthesized arrow function expression.
                 return undefined;
@@ -4463,7 +4463,7 @@ namespace ts {
             // it out, but don't allow any ambiguity, and return 'undefined' if this could be an
             // expression instead.
             return triState === Tristate.True ?
-                parseParenthesizedArrowFunctionExpression(/*allowAmbiguity*/ true, /*disallowReturnTypeInArrowFunction*/ false) :
+                parseParenthesizedArrowFunctionExpression(/*allowAmbiguity*/ true, disallowReturnTypeInArrowFunction) :
                 tryParse(() => parsePossibleParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction));
         }
 
@@ -4471,9 +4471,9 @@ namespace ts {
         //  False       -> There *cannot* be a parenthesized arrow function here.
         //  Unknown     -> There *might* be a parenthesized arrow function here.
         //                 Speculatively look ahead to be sure, and rollback if not.
-        function isParenthesizedArrowFunctionExpression(): Tristate {
+        function isParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction: boolean): Tristate {
             if (token() === SyntaxKind.OpenParenToken || token() === SyntaxKind.LessThanToken || token() === SyntaxKind.AsyncKeyword) {
-                return lookAhead(isParenthesizedArrowFunctionExpressionWorker);
+                return lookAhead(() => isParenthesizedArrowFunctionExpressionWorker(disallowReturnTypeInArrowFunction));
             }
 
             if (token() === SyntaxKind.EqualsGreaterThanToken) {
@@ -4486,7 +4486,7 @@ namespace ts {
             return Tristate.False;
         }
 
-        function isParenthesizedArrowFunctionExpressionWorker() {
+        function isParenthesizedArrowFunctionExpressionWorker(disallowReturnTypeInArrowFunction: boolean) {
             if (token() === SyntaxKind.AsyncKeyword) {
                 nextToken();
                 if (scanner.hasPrecedingLineBreak()) {
@@ -4508,8 +4508,13 @@ namespace ts {
                     // but this is probably what the user intended.
                     const third = nextToken();
                     switch (third) {
-                        case SyntaxKind.EqualsGreaterThanToken:
                         case SyntaxKind.ColonToken:
+                            if (disallowReturnTypeInArrowFunction) {
+                                // "a ? () : ..."
+                                return Tristate.False;
+                            }
+                            return Tristate.True;
+                        case SyntaxKind.EqualsGreaterThanToken:
                         case SyntaxKind.OpenBraceToken:
                             return Tristate.True;
                         default:
@@ -4695,7 +4700,19 @@ namespace ts {
                 }
             }
 
-            const hasReturnColon = token() === SyntaxKind.ColonToken;
+            // Given:
+            //     x ? y => ({ y }) : z => ({ z })
+            // We try to parse the body of the first arrow function by looking at:
+            //     ({ y }) : z => ({ z })
+            // This is a valid arrow function with "z" as the return type.
+            //
+            // But, if we're in the true side of a conditional expression, this colon
+            // terminates the expression, so we cannot allow a return type, even if we aren't
+            // certain whether or not the preceding text was parsed as a parameter list.
+            if (disallowReturnTypeInArrowFunction && token() === SyntaxKind.ColonToken) {
+                return undefined;
+            }
+
             const type = parseReturnType(SyntaxKind.ColonToken, /*isType*/ false);
             if (type && !allowAmbiguity && typeHasArrowFunctionBlockingParseError(type)) {
                 return undefined;
@@ -4731,31 +4748,6 @@ namespace ts {
                 ? parseArrowFunctionExpressionBody(some(modifiers, isAsyncModifier), disallowReturnTypeInArrowFunction)
                 : parseIdentifier();
 
-            // Given:
-            //     x ? y => ({ y }) : z => ({ z })
-            // We try to parse the body of the first arrow function by looking at:
-            //     ({ y }) : z => ({ z })
-            // This is a valid arrow function with "z" as the return type.
-            //
-            // But, if we're in the true side of a conditional expression, this colon
-            // terminates the expression, so we cannot allow a return type if we aren't
-            // certain whether or not the preceding text was parsed as a parameter list.
-            //
-            // For example,
-            //     a() ? (b: number, c?: string): void => d() : e
-            // is determined by isParenthesizedArrowFunctionExpression to unambiguously
-            // be an arrow expression, so we allow a return type.
-            if (disallowReturnTypeInArrowFunction && hasReturnColon) {
-                // However, if the arrow function we were able to parse is followed by another colon
-                // as in:
-                //     a ? (x): string => x : null
-                // Then allow the arrow function, and treat the second colon as terminating
-                // the conditional expression.
-                if (token() !== SyntaxKind.ColonToken) {
-                    return undefined;
-                }
-            }
-
             const node = factory.createArrowFunction(modifiers, typeParameters, parameters, type, equalsGreaterThanToken, body);
             return withJSDoc(finishNode(node, pos), hasJSDoc);
         }
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt
index 0ee29b021a1ef..43cf9de267b85 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.errors.txt
@@ -1,17 +1,20 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,1): error TS2304: Cannot find name 'a'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,11): error TS2304: Cannot find name 'c'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,6): error TS2304: Cannot find name 'b'.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,17): error TS2304: Cannot find name 'd'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,20): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts(1,27): error TS2304: Cannot find name 'f'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts (4 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts (5 errors) ====
     a ? (b) : c => (d) : e => f
     ~
 !!! error TS2304: Cannot find name 'a'.
-              ~
-!!! error TS2304: Cannot find name 'c'.
+         ~
+!!! error TS2304: Cannot find name 'b'.
                     ~
 !!! error TS2304: Cannot find name 'd'.
+                       ~
+!!! error TS1005: ';' expected.
                               ~
 !!! error TS2304: Cannot find name 'f'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.js b/tests/baselines/reference/parserArrowFunctionExpression10.js
index 7681332637b4e..86e1e61bb0716 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.js
@@ -3,4 +3,5 @@ a ? (b) : c => (d) : e => f
 
 
 //// [parserArrowFunctionExpression10.js]
-a ? function (b) { return (d); } : function (e) { return f; };
+a ? (b) : function (c) { return (d); };
+(function (e) { return f; });
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.symbols b/tests/baselines/reference/parserArrowFunctionExpression10.symbols
index df391a0be345d..f30f0b3e3ca49 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.symbols
@@ -1,6 +1,5 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts ===
 a ? (b) : c => (d) : e => f
->b : Symbol(b, Decl(parserArrowFunctionExpression10.ts, 0, 5))
->c : Symbol(c)
+>c : Symbol(c, Decl(parserArrowFunctionExpression10.ts, 0, 9))
 >e : Symbol(e, Decl(parserArrowFunctionExpression10.ts, 0, 20))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression10.types b/tests/baselines/reference/parserArrowFunctionExpression10.types
index e4149fe4cbb5c..8ec7d69c29559 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression10.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression10.types
@@ -1,9 +1,11 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression10.ts ===
 a ? (b) : c => (d) : e => f
->a ? (b) : c => (d) : e => f : (b: any) => c
+>a ? (b) : c => (d) : any
 >a : any
->(b) : c => (d) : (b: any) => c
+>(b) : any
 >b : any
+>c => (d) : (c: any) => any
+>c : any
 >(d) : any
 >d : any
 >e => f : (e: any) => any
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt
index d0ea1c7d179ab..d4ced1fae38a4 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt
@@ -1,11 +1,17 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,1): error TS2304: Cannot find name 'a'.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,11): error TS2304: Cannot find name 'a'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,18): error TS1109: Expression expected.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,19): error TS1005: ';' expected.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts (2 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts (4 errors) ====
     a ? () => a() : (): any => null;
     ~
 !!! error TS2304: Cannot find name 'a'.
               ~
 !!! error TS2304: Cannot find name 'a'.
+                     ~
+!!! error TS1109: Expression expected.
+                      ~
+!!! error TS1005: ';' expected.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.js b/tests/baselines/reference/parserArrowFunctionExpression13.js
index d208d9ba90a1f..f9b67bf58e336 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.js
@@ -3,4 +3,5 @@ a ? () => a() : (): any => null;
 
 
 //// [parserArrowFunctionExpression13.js]
-a ? function () { return a(); } : function () { return null; };
+a ? function () { return a(); } : ();
+(function (any) { return null; });
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.symbols b/tests/baselines/reference/parserArrowFunctionExpression13.symbols
index 643cfcf1a2b78..81ab28ab8cc51 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.symbols
@@ -1,4 +1,4 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts ===
 a ? () => a() : (): any => null;
-No type information for this code.
-No type information for this code.
\ No newline at end of file
+>any : Symbol(any, Decl(parserArrowFunctionExpression13.ts, 0, 19))
+
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.types b/tests/baselines/reference/parserArrowFunctionExpression13.types
index 9341e27b0c30d..7594e1e0469a7 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.types
@@ -1,10 +1,13 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts ===
 a ? () => a() : (): any => null;
->a ? () => a() : (): any => null : () => any
+>a ? () => a() : () : any
 >a : any
 >() => a() : () => any
 >a() : any
 >a : any
->(): any => null : () => any
+>() : any
+> : any
+>any => null : (any: any) => any
+>any : any
 >null : null
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression14.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression14.errors.txt
index b37e09d92ff3a..c19776f77a046 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression14.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression14.errors.txt
@@ -1,14 +1,23 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,1): error TS2304: Cannot find name 'a'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,30): error TS1109: Expression expected.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,37): error TS1109: Expression expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,40): error TS2304: Cannot find name 'd'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,44): error TS1005: ';' expected.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts(1,46): error TS2304: Cannot find name 'e'.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts (3 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts (6 errors) ====
     a() ? (b: number, c?: string): void => d() : e;
     ~
 !!! error TS2304: Cannot find name 'a'.
+                                 ~
+!!! error TS1109: Expression expected.
+                                        ~~
+!!! error TS1109: Expression expected.
                                            ~
 !!! error TS2304: Cannot find name 'd'.
+                                               ~
+!!! error TS1005: ';' expected.
                                                  ~
 !!! error TS2304: Cannot find name 'e'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression14.js b/tests/baselines/reference/parserArrowFunctionExpression14.js
index 2dcaae91f3506..7941718ae24a8 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression14.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression14.js
@@ -3,4 +3,6 @@ a() ? (b: number, c?: string): void => d() : e;
 
 
 //// [parserArrowFunctionExpression14.js]
-a() ? function (b, c) { return d(); } : e;
+a() ?  : void ;
+d();
+e;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression14.symbols b/tests/baselines/reference/parserArrowFunctionExpression14.symbols
index 95584e9f223be..75c6d5ff8b7ff 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression14.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression14.symbols
@@ -1,5 +1,4 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts ===
 a() ? (b: number, c?: string): void => d() : e;
->b : Symbol(b, Decl(parserArrowFunctionExpression14.ts, 0, 7))
->c : Symbol(c, Decl(parserArrowFunctionExpression14.ts, 0, 17))
-
+No type information for this code.
+No type information for this code.
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression14.types b/tests/baselines/reference/parserArrowFunctionExpression14.types
index 1c6d22bb83dc0..4102193f96787 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression14.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression14.types
@@ -1,11 +1,11 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression14.ts ===
 a() ? (b: number, c?: string): void => d() : e;
->a() ? (b: number, c?: string): void => d() : e : any
+>a() ? (b: number, c?: string): void : any
 >a() : any
 >a : any
->(b: number, c?: string): void => d() : (b: number, c?: string) => void
->b : number
->c : string
+> : any
+>void : undefined
+> : any
 >d() : any
 >d : any
 >e : any
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
new file mode 100644
index 0000000000000..60def8ca15fa6
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,10): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,28): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts(1,34): error TS1005: ';' expected.
+
+
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts (3 errors) ====
+    false ? (param): string => param : null
+             ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                               ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                     ~
+!!! error TS1005: ';' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.js b/tests/baselines/reference/parserArrowFunctionExpression15.js
index a18efc84f0975..047b09c6ddec0 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression15.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.js
@@ -3,4 +3,5 @@ false ? (param): string => param : null
 
 
 //// [parserArrowFunctionExpression15.js]
-false ? function (param) { return param; } : null;
+false ? (param) : function (string) { return param; };
+null;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.symbols b/tests/baselines/reference/parserArrowFunctionExpression15.symbols
index 7cb354c7dc912..7750b8d43be97 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression15.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.symbols
@@ -1,5 +1,4 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
 false ? (param): string => param : null
->param : Symbol(param, Decl(parserArrowFunctionExpression15.ts, 0, 9))
->param : Symbol(param, Decl(parserArrowFunctionExpression15.ts, 0, 9))
+>string : Symbol(string, Decl(parserArrowFunctionExpression15.ts, 0, 16))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression15.types b/tests/baselines/reference/parserArrowFunctionExpression15.types
index 4640763862112..ec808c729eece 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression15.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression15.types
@@ -1,9 +1,11 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression15.ts ===
 false ? (param): string => param : null
->false ? (param): string => param : null : (param: any) => string
+>false ? (param): string => param : any
 >false : false
->(param): string => param : (param: any) => string
+>(param) : any
 >param : any
+>string => param : (string: any) => any
+>string : any
 >param : any
 >null : null
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
new file mode 100644
index 0000000000000..740144391e298
--- /dev/null
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,17): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,35): error TS2304: Cannot find name 'param'.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts(1,48): error TS1005: ';' expected.
+
+
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts (3 errors) ====
+    true ? false ? (param): string => param : null : null
+                    ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                      ~~~~~
+!!! error TS2304: Cannot find name 'param'.
+                                                   ~
+!!! error TS1005: ';' expected.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.js b/tests/baselines/reference/parserArrowFunctionExpression16.js
index 8d0404c91c853..a2b2fff3aad85 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression16.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.js
@@ -3,4 +3,5 @@ true ? false ? (param): string => param : null : null
 
 
 //// [parserArrowFunctionExpression16.js]
-true ? false ? function (param) { return param; } : null : null;
+true ? false ? (param) : function (string) { return param; } : null;
+null;
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.symbols b/tests/baselines/reference/parserArrowFunctionExpression16.symbols
index f2a4ff04df134..684b74408ccd5 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression16.symbols
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.symbols
@@ -1,5 +1,4 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
 true ? false ? (param): string => param : null : null
->param : Symbol(param, Decl(parserArrowFunctionExpression16.ts, 0, 16))
->param : Symbol(param, Decl(parserArrowFunctionExpression16.ts, 0, 16))
+>string : Symbol(string, Decl(parserArrowFunctionExpression16.ts, 0, 23))
 
diff --git a/tests/baselines/reference/parserArrowFunctionExpression16.types b/tests/baselines/reference/parserArrowFunctionExpression16.types
index fffd623adac0d..dbe5cc2e81733 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression16.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression16.types
@@ -1,11 +1,13 @@
 === tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression16.ts ===
 true ? false ? (param): string => param : null : null
->true ? false ? (param): string => param : null : null : (param: any) => string
+>true ? false ? (param): string => param : null : any
 >true : true
->false ? (param): string => param : null : (param: any) => string
+>false ? (param): string => param : any
 >false : false
->(param): string => param : (param: any) => string
+>(param) : any
 >param : any
+>string => param : (string: any) => any
+>string : any
 >param : any
 >null : null
 >null : null

From fb6ba846138263e6501fcb707381ffaa8fec59e2 Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Wed, 20 Apr 2022 16:16:51 -0700
Subject: [PATCH 7/7] Make (): unambiguous again

---
 src/compiler/parser.ts                            | 15 +++++----------
 .../parserArrowFunctionExpression13.errors.txt    |  9 +++------
 .../reference/parserArrowFunctionExpression13.js  |  2 +-
 .../parserArrowFunctionExpression13.types         |  1 -
 4 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 20cacf711592e..ffe5f079c8c78 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -4452,7 +4452,7 @@ namespace ts {
         }
 
         function tryParseParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction: boolean): Expression | undefined {
-            const triState = isParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction);
+            const triState = isParenthesizedArrowFunctionExpression();
             if (triState === Tristate.False) {
                 // It's definitely not a parenthesized arrow function expression.
                 return undefined;
@@ -4471,9 +4471,9 @@ namespace ts {
         //  False       -> There *cannot* be a parenthesized arrow function here.
         //  Unknown     -> There *might* be a parenthesized arrow function here.
         //                 Speculatively look ahead to be sure, and rollback if not.
-        function isParenthesizedArrowFunctionExpression(disallowReturnTypeInArrowFunction: boolean): Tristate {
+        function isParenthesizedArrowFunctionExpression(): Tristate {
             if (token() === SyntaxKind.OpenParenToken || token() === SyntaxKind.LessThanToken || token() === SyntaxKind.AsyncKeyword) {
-                return lookAhead(() => isParenthesizedArrowFunctionExpressionWorker(disallowReturnTypeInArrowFunction));
+                return lookAhead(isParenthesizedArrowFunctionExpressionWorker);
             }
 
             if (token() === SyntaxKind.EqualsGreaterThanToken) {
@@ -4486,7 +4486,7 @@ namespace ts {
             return Tristate.False;
         }
 
-        function isParenthesizedArrowFunctionExpressionWorker(disallowReturnTypeInArrowFunction: boolean) {
+        function isParenthesizedArrowFunctionExpressionWorker() {
             if (token() === SyntaxKind.AsyncKeyword) {
                 nextToken();
                 if (scanner.hasPrecedingLineBreak()) {
@@ -4508,13 +4508,8 @@ namespace ts {
                     // but this is probably what the user intended.
                     const third = nextToken();
                     switch (third) {
-                        case SyntaxKind.ColonToken:
-                            if (disallowReturnTypeInArrowFunction) {
-                                // "a ? () : ..."
-                                return Tristate.False;
-                            }
-                            return Tristate.True;
                         case SyntaxKind.EqualsGreaterThanToken:
+                        case SyntaxKind.ColonToken:
                         case SyntaxKind.OpenBraceToken:
                             return Tristate.True;
                         default:
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt b/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt
index d4ced1fae38a4..8e4df9842c146 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.errors.txt
@@ -1,17 +1,14 @@
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,1): error TS2304: Cannot find name 'a'.
 tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,11): error TS2304: Cannot find name 'a'.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,18): error TS1109: Expression expected.
-tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,19): error TS1005: ';' expected.
+tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts(1,19): error TS1109: Expression expected.
 
 
-==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts (4 errors) ====
+==== tests/cases/conformance/parser/ecmascript5/ArrowFunctionExpressions/parserArrowFunctionExpression13.ts (3 errors) ====
     a ? () => a() : (): any => null;
     ~
 !!! error TS2304: Cannot find name 'a'.
               ~
 !!! error TS2304: Cannot find name 'a'.
-                     ~
-!!! error TS1109: Expression expected.
                       ~
-!!! error TS1005: ';' expected.
+!!! error TS1109: Expression expected.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.js b/tests/baselines/reference/parserArrowFunctionExpression13.js
index f9b67bf58e336..5bc8a18e946c6 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.js
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.js
@@ -3,5 +3,5 @@ a ? () => a() : (): any => null;
 
 
 //// [parserArrowFunctionExpression13.js]
-a ? function () { return a(); } : ();
+a ? function () { return a(); } : ;
 (function (any) { return null; });
diff --git a/tests/baselines/reference/parserArrowFunctionExpression13.types b/tests/baselines/reference/parserArrowFunctionExpression13.types
index 7594e1e0469a7..6eaa57cd45d59 100644
--- a/tests/baselines/reference/parserArrowFunctionExpression13.types
+++ b/tests/baselines/reference/parserArrowFunctionExpression13.types
@@ -5,7 +5,6 @@ a ? () => a() : (): any => null;
 >() => a() : () => any
 >a() : any
 >a : any
->() : any
 > : any
 >any => null : (any: any) => any
 >any : any