Parse MacroVar with empty expressions: %var{}

spec/compiler/formatter/formatter_spec.cr

@@ -1387,6 +1387,7 @@ describe Crystal::Formatter do
   assert_format "macro foo\n  %foo\nend"
   assert_format "macro foo\n  %foo{x.id+2}\nend", "macro foo\n  %foo{x.id + 2}\nend"
   assert_format "macro foo\n  %foo{x,y}\nend", "macro foo\n  %foo{x, y}\nend"
+  assert_format "macro foo;%var{}end", "macro foo\n%var{}end"
   assert_format "def foo : Int32\n  1\nend"
   assert_format "class Foo\n  macro foo\n    1\n  end\nend"
   assert_format "   {{ 1 + 2 }}", "{{ 1 + 2 }}"

spec/compiler/parser/parser_spec.cr

@@ -1484,6 +1484,7 @@ module Crystal
 
     it_parses "macro foo;%var;end", Macro.new("foo", [] of Arg, Expressions.from([MacroVar.new("var"), MacroLiteral.new(";")] of ASTNode))
     it_parses "macro foo;%var{1, x} = hello;end", Macro.new("foo", [] of Arg, Expressions.from([MacroVar.new("var", [1.int32, "x".var] of ASTNode), MacroLiteral.new(" = hello;")] of ASTNode))
+    it_parses "macro foo;%var{}end", Macro.new("foo", [] of Arg, Expressions.from([MacroVar.new("var", [] of ASTNode)] of ASTNode))
 
     # #4087
     describe "suffix `if`/`unless` in macros after macro var" do

spec/compiler/parser/to_s_spec.cr

@@ -59,6 +59,7 @@ describe "ASTNode#to_s" do
   expect_to_s %(macro foo\n  %bar = 1\nend)
   expect_to_s %(macro foo\n  %bar = 1; end)
   expect_to_s %(macro foo\n  %bar{1, x} = 1\nend)
+  expect_to_s %(macro foo\n  %bar{}\nend)
   expect_to_s %({% foo %})
   expect_to_s %({{ foo }})
   expect_to_s %({% if foo %}\n  foo_then\n{% end %})

src/compiler/crystal/syntax/parser.cr

@@ -3325,15 +3325,12 @@ module Crystal
       next_token
 
       exps = [] of ASTNode
-      while true
+      while !@token.type.op_rcurly?
         exps << parse_expression_inside_macro
         skip_space
         case @token.type
         when .op_comma?
           next_token_skip_space
-          if @token.type.op_rcurly?
-            break
-          end
         when .op_rcurly?
           break
         else