Add multi-line formatting support to Generic formatter visitor (#16430)

Author: Blacksmoke16

spec/compiler/formatter/formatter_spec.cr

@@ -143,6 +143,13 @@ describe Crystal::Formatter do
   assert_format "NamedTuple(\n  a: Int32,)", "NamedTuple(\n  a: Int32,\n)"
   assert_format "class Foo\n  NamedTuple(\n    a: Int32,\n  )\nend"
 
+  # Multi-line generic type with inline comments (issue #11328)
+  assert_format "Tuple(\n  Int32, # first\n  String, # second\n)", "Tuple(\n  Int32,  # first\n  String, # second\n)"
+  assert_format "Tuple(\n  Int32, # first\n  String, # second\n  Bool,\n)", "Tuple(\n  Int32,  # first\n  String, # second\n  Bool,\n)"
+  assert_format "Tuple(\n  Int32, # first\n  String # adds trailing comma\n)", "Tuple(\n  Int32,  # first\n  String, # adds trailing comma\n)"
+  assert_format "Hash(\n  String, # key\n  Int32, # value\n)", "Hash(\n  String, # key\n  Int32,  # value\n)"
+  assert_format "Tuple(\n  Int32,\n  String\n)", "Tuple(\n  Int32,\n  String,\n)"
+
   assert_format "::Tuple(T)"
   assert_format "::NamedTuple(T)"
   assert_format "::Pointer(T)"

src/compiler/crystal/tools/formatter.cr

@@ -1205,15 +1205,14 @@ module Crystal
       accept name
       skip_space_or_newline
 
-      write_token :OP_LPAREN
-      skip_space
-
       # Given that generic type arguments are always inside parentheses
       # we can start counting them from 0 inside them.
       old_paren_count = @paren_count
       @paren_count = 0
 
       if named_args = node.named_args
+        write_token :OP_LPAREN
+        skip_space
         has_newlines, _, _ = format_named_args([] of ASTNode, named_args, @indent + 2)
         # `format_named_args` doesn't skip trailing comma
         if @paren_count == 0 && @token.type.op_comma?
@@ -1224,23 +1223,12 @@ module Crystal
             write_indent
           end
         end
+        skip_space_or_newline if @paren_count == 0
+        write_token :OP_RPAREN
       else
-        skip_space_or_newline
-        node.type_vars.each_with_index do |type_var, i|
-          accept type_var
-          if @paren_count == 0
-            skip_space_or_newline
-            if @token.type.op_comma?
-              write ", " unless last?(i, node.type_vars)
-              next_token_skip_space_or_newline
-            end
-          end
-        end
+        format_literal_elements(node.type_vars, :OP_LPAREN, :OP_RPAREN)
       end
 
-      skip_space_or_newline if @paren_count == 0
-      write_token :OP_RPAREN
-
       # Restore the old parentheses count
       @paren_count = old_paren_count