Add return type to function declarations

grammar.js

@@ -283,6 +283,7 @@ module.exports = grammar({
     _function_declaration_common: ($) => seq(
       field("name", $.identifier),
       field("parameters", $.parameters),
+      optional(seq(":", field("return_type", $.identifier))),
     ),
 
     parameters: ($) => seq(

src/grammar.json

@@ -1277,6 +1277,31 @@
             "type": "SYMBOL",
             "name": "parameters"
           }
+        },
+        {
+          "type": "CHOICE",
+          "members": [
+            {
+              "type": "SEQ",
+              "members": [
+                {
+                  "type": "STRING",
+                  "value": ":"
+                },
+                {
+                  "type": "FIELD",
+                  "name": "return_type",
+                  "content": {
+                    "type": "SYMBOL",
+                    "name": "identifier"
+                  }
+                }
+              ]
+            },
+            {
+              "type": "BLANK"
+            }
+          ]
         }
       ]
     },

src/node-types.json

@@ -1012,6 +1012,16 @@
             "named": true
           }
         ]
+      },
+      "return_type": {
+        "multiple": false,
+        "required": false,
+        "types": [
+          {
+            "type": "identifier",
+            "named": true
+          }
+        ]
       }
     }
   },
@@ -1452,6 +1462,16 @@
             "named": true
           }
         ]
+      },
+      "return_type": {
+        "multiple": false,
+        "required": false,
+        "types": [
+          {
+            "type": "identifier",
+            "named": true
+          }
+        ]
       }
     }
   },

test/corpus/declarations.txt

@@ -130,6 +130,25 @@ function func(a: int, b: int) = "string"
       type: (identifier))
     body: (string_literal)))
 
+================================================================================
+Function declaration return type
+================================================================================
+
+function func(a: int, b: int) : string = "string"
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (function_declaration
+    name: (identifier)
+    parameters: (parameters
+      name: (identifier)
+      type: (identifier)
+      name: (identifier)
+      type: (identifier))
+    return_type: (identifier)
+    body: (string_literal)))
+
 ================================================================================
 Function declaration single parameter
 ================================================================================
@@ -173,6 +192,20 @@ primitive prim()
     name: (identifier)
     parameters: (parameters)))
 
+================================================================================
+Primitive declaration with return type
+================================================================================
+
+primitive prim() : int
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (primitive_declaration
+    name: (identifier)
+    parameters: (parameters)
+    return_type: (identifier)))
+
 ================================================================================
 Variable declaration
 ================================================================================