From 697d1042ebf8d86368dd6233a581d44283a8b3a4 Mon Sep 17 00:00:00 2001
From: Alexander T <alexander.tarasyuk@outlook.com>
Date: Thu, 2 Apr 2020 01:38:10 +0300
Subject: [PATCH] fix(37519): forbid trailing comma in a index signature
 (#37535)

---
 src/compiler/checker.ts                       |  1 +
 src/compiler/diagnosticMessages.json          |  4 ++++
 ...indexSignatureWithTrailingComma.errors.txt | 24 +++++++++++++++++++
 .../indexSignatureWithTrailingComma.js        | 20 ++++++++++++++++
 .../indexSignatureWithTrailingComma.symbols   | 23 ++++++++++++++++++
 .../indexSignatureWithTrailingComma.types     | 22 +++++++++++++++++
 .../indexSignatureWithTrailingComma.ts        | 11 +++++++++
 7 files changed, 105 insertions(+)
 create mode 100644 tests/baselines/reference/indexSignatureWithTrailingComma.errors.txt
 create mode 100644 tests/baselines/reference/indexSignatureWithTrailingComma.js
 create mode 100644 tests/baselines/reference/indexSignatureWithTrailingComma.symbols
 create mode 100644 tests/baselines/reference/indexSignatureWithTrailingComma.types
 create mode 100644 tests/cases/compiler/indexSignatureWithTrailingComma.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2550e8bd8bc..04628ed4c1d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -36658,6 +36658,7 @@ namespace ts {
                     return grammarErrorOnNode(node, Diagnostics.An_index_signature_must_have_exactly_one_parameter);
                 }
             }
+            checkGrammarForDisallowedTrailingComma(node.parameters, Diagnostics.An_index_signature_cannot_have_a_trailing_comma);
             if (parameter.dotDotDotToken) {
                 return grammarErrorOnNode(parameter.dotDotDotToken, Diagnostics.An_index_signature_cannot_have_a_rest_parameter);
             }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 67ff8c35558..d1e13c77752 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -83,6 +83,10 @@
         "category": "Error",
         "code": 1024
     },
+    "An index signature cannot have a trailing comma.": {
+        "category": "Error",
+        "code": 1025
+    },
     "Accessibility modifier already seen.": {
         "category": "Error",
         "code": 1028
diff --git a/tests/baselines/reference/indexSignatureWithTrailingComma.errors.txt b/tests/baselines/reference/indexSignatureWithTrailingComma.errors.txt
new file mode 100644
index 00000000000..eb56c2d511c
--- /dev/null
+++ b/tests/baselines/reference/indexSignatureWithTrailingComma.errors.txt
@@ -0,0 +1,24 @@
+tests/cases/compiler/indexSignatureWithTrailingComma.ts(2,17): error TS1025: An index signature cannot have a trailing comma.
+tests/cases/compiler/indexSignatureWithTrailingComma.ts(6,17): error TS1025: An index signature cannot have a trailing comma.
+tests/cases/compiler/indexSignatureWithTrailingComma.ts(10,17): error TS1025: An index signature cannot have a trailing comma.
+
+
+==== tests/cases/compiler/indexSignatureWithTrailingComma.ts (3 errors) ====
+    type A = {
+        [key: string,]: string;
+                    ~
+!!! error TS1025: An index signature cannot have a trailing comma.
+    };
+    
+    interface B {
+        [key: string,]: string;
+                    ~
+!!! error TS1025: An index signature cannot have a trailing comma.
+    }
+    
+    class C {
+        [key: string,]: null;
+                    ~
+!!! error TS1025: An index signature cannot have a trailing comma.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/indexSignatureWithTrailingComma.js b/tests/baselines/reference/indexSignatureWithTrailingComma.js
new file mode 100644
index 00000000000..d96d32747d4
--- /dev/null
+++ b/tests/baselines/reference/indexSignatureWithTrailingComma.js
@@ -0,0 +1,20 @@
+//// [indexSignatureWithTrailingComma.ts]
+type A = {
+    [key: string,]: string;
+};
+
+interface B {
+    [key: string,]: string;
+}
+
+class C {
+    [key: string,]: null;
+}
+
+
+//// [indexSignatureWithTrailingComma.js]
+var C = /** @class */ (function () {
+    function C() {
+    }
+    return C;
+}());
diff --git a/tests/baselines/reference/indexSignatureWithTrailingComma.symbols b/tests/baselines/reference/indexSignatureWithTrailingComma.symbols
new file mode 100644
index 00000000000..9a8a9ac4175
--- /dev/null
+++ b/tests/baselines/reference/indexSignatureWithTrailingComma.symbols
@@ -0,0 +1,23 @@
+=== tests/cases/compiler/indexSignatureWithTrailingComma.ts ===
+type A = {
+>A : Symbol(A, Decl(indexSignatureWithTrailingComma.ts, 0, 0))
+
+    [key: string,]: string;
+>key : Symbol(key, Decl(indexSignatureWithTrailingComma.ts, 1, 5))
+
+};
+
+interface B {
+>B : Symbol(B, Decl(indexSignatureWithTrailingComma.ts, 2, 2))
+
+    [key: string,]: string;
+>key : Symbol(key, Decl(indexSignatureWithTrailingComma.ts, 5, 5))
+}
+
+class C {
+>C : Symbol(C, Decl(indexSignatureWithTrailingComma.ts, 6, 1))
+
+    [key: string,]: null;
+>key : Symbol(key, Decl(indexSignatureWithTrailingComma.ts, 9, 5))
+}
+
diff --git a/tests/baselines/reference/indexSignatureWithTrailingComma.types b/tests/baselines/reference/indexSignatureWithTrailingComma.types
new file mode 100644
index 00000000000..095e97c6e2d
--- /dev/null
+++ b/tests/baselines/reference/indexSignatureWithTrailingComma.types
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/indexSignatureWithTrailingComma.ts ===
+type A = {
+>A : A
+
+    [key: string,]: string;
+>key : string
+
+};
+
+interface B {
+    [key: string,]: string;
+>key : string
+}
+
+class C {
+>C : C
+
+    [key: string,]: null;
+>key : string
+>null : null
+}
+
diff --git a/tests/cases/compiler/indexSignatureWithTrailingComma.ts b/tests/cases/compiler/indexSignatureWithTrailingComma.ts
new file mode 100644
index 00000000000..0f3fec5ad26
--- /dev/null
+++ b/tests/cases/compiler/indexSignatureWithTrailingComma.ts
@@ -0,0 +1,11 @@
+type A = {
+    [key: string,]: string;
+};
+
+interface B {
+    [key: string,]: string;
+}
+
+class C {
+    [key: string,]: null;
+}