Fix parenthesized expressions in braceless if conditions

Fixes #263 and #342
`_if_condition` extracted from `if_expression` and given a magic dynamic
precedence of 4

corpus/expressions.txt

@@ -404,6 +404,11 @@ class C:
     else
       ()
 
+    if (a) || b(c) then return true
+
+    if (a) && b.c then
+      ()
+
 --------------------------------------------------------------------------------
 
 (compilation_unit
@@ -445,6 +450,27 @@ class C:
             (indented_block
               (unit)
               (comment))
+            (indented_block
+              (unit)))
+          (if_expression
+            (infix_expression
+              (parenthesized_expression
+                (identifier))
+              (operator_identifier)
+              (call_expression
+                (identifier)
+                (arguments
+                  (identifier))))
+            (return_expression
+              (boolean_literal)))
+          (if_expression
+            (infix_expression
+              (parenthesized_expression
+                (identifier))
+              (operator_identifier)
+              (field_expression
+                (identifier)
+                (identifier)))
             (indented_block
               (unit))))))))
 

grammar.js

@@ -92,6 +92,8 @@ module.exports = grammar({
     // 'for'  operator_identifier  ':'  _annotated_type  •  ':'  …
     [$._type, $.compound_type],
     [$.lambda_expression, $.modifiers],
+    // 'if'  parenthesized_expression  •  '{'  …
+    [$._if_condition, $._simple_expression],
   ],
 
   word: $ => $._alpha_identifier,
@@ -1104,22 +1106,25 @@ module.exports = grammar({
       ),
 
     if_expression: $ =>
-      prec.right(
-        PREC.control,
-        seq(
-          optional($.inline_modifier),
-          "if",
-          field(
-            "condition",
-            choice(
-              $.parenthesized_expression,
-              seq($._indentable_expression, "then"),
-            ),
-          ),
-          field("consequence", $._indentable_expression),
-          optional(seq("else", field("alternative", $._indentable_expression))),
-        ),
-      ),
+      prec.right(PREC.control, seq(
+        optional($.inline_modifier),
+        "if",
+        field(
+          "condition",
+          $._if_condition,
+        ),
+        field("consequence", $._indentable_expression),
+        optional(seq("else", field("alternative", $._indentable_expression))),
+      )),
+
+    // NOTE(susliko): _if_condition and its magic dynamic precedence were introduced as a fix to
+    // https://github.com/tree-sitter/tree-sitter-scala/issues/263 and
+    // https://github.com/tree-sitter/tree-sitter-scala/issues/342 
+    // Neither do I understand why this works, nor have I found a better solution
+    _if_condition: $ => prec.dynamic(4, choice(
+      $.parenthesized_expression,
+      seq($._indentable_expression, "then"),
+    )),
 
     /*
      *   MatchClause       ::=  'match' <<< CaseClauses >>>

test/highlight/basics.scala

@@ -26,19 +26,19 @@ object Hello {
   trait Test {
 // ^ keyword 
 //       ^ type
-     def meth(i: Int)(implicit x: Boolean) = ???
+    def meth(i: Int)(implicit x: Boolean) = ???
 //    ^keyword.function  
 //                       ^keyword    
 //                                  ^type    
 //        ^method
-//                             ^parameter 
+//                            ^parameter 
 
-  val anonFun: Int => Int = (a: Int) => a
-//      ^variable
-//             ^type
-//                 ^operator
-//                    ^type
-//                           ^parameter
+    val anonFun: Int => Int = (a: Int) => a
+  //      ^variable
+  //             ^type
+  //                 ^operator
+  //                    ^type
+  //                           ^parameter
   }
 
   protected abstract class Bla(test: String)