C#12 lambda optional and params

Author: wise0704

grammars/csharp.tmLanguage

@@ -7950,6 +7950,10 @@
                     <key>include</key>
                     <string>#implicit-anonymous-function-parameter</string>
                   </dict>
+                  <dict>
+                    <key>include</key>
+                    <string>#default-argument</string>
+                  </dict>
                   <dict>
                     <key>include</key>
                     <string>#punctuation-comma</string>
@@ -8097,7 +8101,7 @@
       <dict>
         <key>match</key>
         <string>(?x)
-(?:\b(ref|out|in)\b\s*)?
+(?:\b(ref|params|out|in)\b\s*)?
 (?&lt;type_name&gt;
   (?:
     (?:
@@ -8152,6 +8156,28 @@
         <key>name</key>
         <string>entity.name.variable.parameter.cs</string>
       </dict>
+      <key>default-argument</key>
+      <dict>
+        <key>begin</key>
+        <string>=</string>
+        <key>beginCaptures</key>
+        <dict>
+          <key>0</key>
+          <dict>
+            <key>name</key>
+            <string>keyword.operator.assignment.cs</string>
+          </dict>
+        </dict>
+        <key>end</key>
+        <string>(?=,|\))</string>
+        <key>patterns</key>
+        <array>
+          <dict>
+            <key>include</key>
+            <string>#expression</string>
+          </dict>
+        </array>
+      </dict>
       <key>type</key>
       <dict>
         <key>patterns</key>

grammars/csharp.tmLanguage.cson

@@ -4801,6 +4801,9 @@ repository:
               {
                 include: "#implicit-anonymous-function-parameter"
               }
+              {
+                include: "#default-argument"
+              }
               {
                 include: "#punctuation-comma"
               }
@@ -4891,7 +4894,7 @@ repository:
   "explicit-anonymous-function-parameter":
     match: '''
       (?x)
-      (?:\\b(ref|out|in)\\b\\s*)?
+      (?:\\b(ref|params|out|in)\\b\\s*)?
       (?<type_name>
         (?:
           (?:
@@ -4930,6 +4933,17 @@ repository:
   "implicit-anonymous-function-parameter":
     match: "\\@?[_[:alpha:]][_[:alnum:]]*\\b"
     name: "entity.name.variable.parameter.cs"
+  "default-argument":
+    begin: "="
+    beginCaptures:
+      "0":
+        name: "keyword.operator.assignment.cs"
+    end: "(?=,|\\))"
+    patterns: [
+      {
+        include: "#expression"
+      }
+    ]
   type:
     patterns: [
       {

src/csharp.tmLanguage.yml

@@ -3124,6 +3124,7 @@ repository:
           - include: '#comment'
           - include: '#explicit-anonymous-function-parameter'
           - include: '#implicit-anonymous-function-parameter'
+          - include: '#default-argument'
           - include: '#punctuation-comma'
         5: { name: punctuation.parenthesis.close.cs }
         6: { name: keyword.operator.arrow.cs }
@@ -3169,7 +3170,7 @@ repository:
   explicit-anonymous-function-parameter:
     match: |-
       (?x)
-      (?:\b(ref|out|in)\b\s*)?
+      (?:\b(ref|params|out|in)\b\s*)?
       (?<type_name>
         (?:
           (?:
@@ -3208,6 +3209,14 @@ repository:
     match: \@?[_[:alpha:]][_[:alnum:]]*\b
     name: entity.name.variable.parameter.cs
 
+  default-argument:
+    begin: =
+    beginCaptures:
+      0: { name: keyword.operator.assignment.cs }
+    end: (?=,|\))
+    patterns:
+    - include: '#expression'
+
   type:
     patterns:
     - include: '#comment'

test/expressions.tests.ts

@@ -1268,6 +1268,49 @@ _ = delegate /*comment*/ () /*comment*/ {  };`);
           Token.Punctuation.Semicolon,
         ]);
       });
+
+      it("lambda expression optional parameter (issue #294)", async () => {
+        const input = Input.InMethod(`_ = (int addTo = 2) => addTo + 1;`);
+        const tokens = await tokenize(input);
+
+        tokens.should.deep.equal([
+          Token.Variable.ReadWrite("_"),
+          Token.Operator.Assignment,
+          Token.Punctuation.OpenParen,
+          Token.PrimitiveType.Int,
+          Token.Identifier.ParameterName("addTo"),
+          Token.Operator.Assignment,
+          Token.Literal.Numeric.Decimal("2"),
+          Token.Punctuation.CloseParen,
+          Token.Operator.Arrow,
+          Token.Variable.ReadWrite("addTo"),
+          Token.Operator.Arithmetic.Addition,
+          Token.Literal.Numeric.Decimal("1"),
+          Token.Punctuation.Semicolon,
+        ]);
+      });
+
+      it("lambda expression params array parameter (issue #294)", async () => {
+        const input = Input.InMethod(`_ = (params object[] arr) => arr.Length;`);
+        const tokens = await tokenize(input);
+
+        tokens.should.deep.equal([
+          Token.Variable.ReadWrite("_"),
+          Token.Operator.Assignment,
+          Token.Punctuation.OpenParen,
+          Token.Keyword.Modifier.Params,
+          Token.PrimitiveType.Object,
+          Token.Punctuation.OpenBracket,
+          Token.Punctuation.CloseBracket,
+          Token.Identifier.ParameterName("arr"),
+          Token.Punctuation.CloseParen,
+          Token.Operator.Arrow,
+          Token.Variable.Object("arr"),
+          Token.Punctuation.Accessor,
+          Token.Variable.Property("Length"),
+          Token.Punctuation.Semicolon,
+        ]);
+      });
     });
 
     describe("Anonymous Objects", () => {