Allow newlines before '(' in call expressions in when conditions (#53)

In Kotlin, newlines are not allowed before `(` in call expressions.
However, there is an exception in when conditions: newlines are allowed
there! This is not specified in the Kotlin specifications but the Kotlin
compiler behaves like this.

To fix this, we have to copy the expression nonterminal in
`when_condition` and change the `call_expression` node with another one
that allows newlines. Also, changes should be made in the lexer to allow
this.

Author: afroozeh

grammar.js

@@ -236,11 +236,13 @@ module.exports = grammar({
     "]",
     "${",
     $._not_is,
+    $._external_nl_when_condition,
   ],
 
   supertypes: $ => [
     $.expression,
     $.jump_expression,
+    $.when_condition_expression
   ],
 
   word: $ => $._alpha_identifier,
@@ -836,6 +838,15 @@ module.exports = grammar({
       $._loop_statement
     ),
 
+    when_condition_expression: $ => choice(
+      $._unary_expression,
+      $._binary_expression,
+      $._when_condition_primary_expression,
+      $.jump_expression,
+      $.assignment,
+      $._loop_statement
+    ),
+
     // Unary expressions
 
     _unary_expression: $ => choice(
@@ -875,6 +886,13 @@ module.exports = grammar({
       $._call_arguments
     )),
 
+    when_condition_call_expression: $ => prec("call", seq(
+      field("expression", $.expression), 
+      optional($.type_arguments),
+      repeat($._external_nl_when_condition),
+      $._call_arguments
+    )),
+
     // It's not possible to resolve the ambiguity between explicit delegation and calls with last lambda argument.
     // For example:
     //   class Derived(b: Base) : Base by b {
@@ -1110,6 +1128,11 @@ module.exports = grammar({
       $._non_call_primary_expression
     ),
 
+    _when_condition_primary_expression: $ => choice(
+      $.when_condition_call_expression,
+      $._non_call_primary_expression
+    ),
+
     // we need to give parenthesized expression a lower dynamic precedence to resolve ambiguities like
     // @Annotation() in favor of a single annotation rather than an annotation of a parenthesized expression.
     parenthesized_expression: $ => prec.dynamic(-1, seq("(", repeat($._NL), $.expression, repeat($._NL), ")")),
@@ -1336,7 +1359,7 @@ module.exports = grammar({
     ),
 
     when_condition: $ => choice(
-      $.expression,
+      $.when_condition_expression,
       $.range_test,
       $.type_test
     ),

src/grammar.json

@@ -4192,6 +4192,35 @@
         }
       ]
     },
+    "when_condition_expression": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "SYMBOL",
+          "name": "_unary_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_binary_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_when_condition_primary_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "jump_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "assignment"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_loop_statement"
+        }
+      ]
+    },
     "_unary_expression": {
       "type": "CHOICE",
       "members": [
@@ -4364,6 +4393,46 @@
         ]
       }
     },
+    "when_condition_call_expression": {
+      "type": "PREC",
+      "value": "call",
+      "content": {
+        "type": "SEQ",
+        "members": [
+          {
+            "type": "FIELD",
+            "name": "expression",
+            "content": {
+              "type": "SYMBOL",
+              "name": "expression"
+            }
+          },
+          {
+            "type": "CHOICE",
+            "members": [
+              {
+                "type": "SYMBOL",
+                "name": "type_arguments"
+              },
+              {
+                "type": "BLANK"
+              }
+            ]
+          },
+          {
+            "type": "REPEAT",
+            "content": {
+              "type": "SYMBOL",
+              "name": "_external_nl_when_condition"
+            }
+          },
+          {
+            "type": "SYMBOL",
+            "name": "_call_arguments"
+          }
+        ]
+      }
+    },
     "simple_call_expression": {
       "type": "PREC",
       "value": "call",
@@ -5675,6 +5744,19 @@
         }
       ]
     },
+    "_when_condition_primary_expression": {
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "SYMBOL",
+          "name": "when_condition_call_expression"
+        },
+        {
+          "type": "SYMBOL",
+          "name": "_non_call_primary_expression"
+        }
+      ]
+    },
     "parenthesized_expression": {
       "type": "PREC_DYNAMIC",
       "value": -1,
@@ -7128,7 +7210,7 @@
       "members": [
         {
           "type": "SYMBOL",
-          "name": "expression"
+          "name": "when_condition_expression"
         },
         {
           "type": "SYMBOL",
@@ -9669,12 +9751,17 @@
     {
       "type": "SYMBOL",
       "name": "_not_is"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "_external_nl_when_condition"
     }
   ],
   "inline": [],
   "supertypes": [
     "expression",
-    "jump_expression"
+    "jump_expression",
+    "when_condition_expression"
   ],
   "reserved": {}
 }