Add MacroIf#is_unless? AST node method

spec/compiler/macro/macro_methods_spec.cr

@@ -2726,6 +2726,11 @@ module Crystal
       it "executes else" do
         assert_macro %({{x.else}}), "\"foo\"", {x: MacroIf.new(BoolLiteral.new(true), StringLiteral.new("test"), StringLiteral.new("foo"))}
       end
+
+      it "executes is_unless?" do
+        assert_macro %({{x.is_unless?}}), "true", {x: MacroIf.new(BoolLiteral.new(true), StringLiteral.new("test"), StringLiteral.new("foo"), is_unless: true)}
+        assert_macro %({{x.is_unless?}}), "false", {x: MacroIf.new(BoolLiteral.new(false), StringLiteral.new("test"), StringLiteral.new("foo"), is_unless: false)}
+      end
     end
 
     describe "macro for methods" do

src/compiler/crystal/macros.cr

@@ -2361,14 +2361,20 @@ module Crystal::Macros
     end
   end
 
-  # An `if` inside a macro, e.g.
+  # An `if`/`unless` inside a macro, e.g.
   #
   # ```
   # {% if cond %}
   #   puts "Then"
   # {% else %}
   #   puts "Else"
   # {% end %}
+  #
+  # {% unless cond %}
+  #   puts "Then"
+  # {% else %}
+  #   puts "Else"
+  # {% end %}
   # ```
   class MacroIf < ASTNode
     # The condition of the `if` clause.
@@ -2382,6 +2388,10 @@ module Crystal::Macros
     # The `else` branch of the `if`.
     def else : ASTNode
     end
+
+    # Returns `true` if this node represents an `unless` conditional, otherwise returns `false`.
+    def is_unless? : BoolLiteral
+    end
   end
 
   # A `for` loop inside a macro, e.g.

src/compiler/crystal/macros/methods.cr

@@ -1541,6 +1541,8 @@ module Crystal
         interpret_check_args { @then }
       when "else"
         interpret_check_args { @else }
+      when "is_unless?"
+        interpret_check_args { BoolLiteral.new @is_unless }
       else
         super
       end

src/compiler/crystal/syntax/ast.cr

@@ -2238,8 +2238,9 @@ module Crystal
     property cond : ASTNode
     property then : ASTNode
     property else : ASTNode
+    property? is_unless : Bool
 
-    def initialize(@cond, a_then = nil, a_else = nil)
+    def initialize(@cond, a_then = nil, a_else = nil, @is_unless : Bool = false)
       @then = Expressions.from a_then
       @else = Expressions.from a_else
     end
@@ -2251,10 +2252,10 @@ module Crystal
     end
 
     def clone_without_location
-      MacroIf.new(@cond.clone, @then.clone, @else.clone)
+      MacroIf.new(@cond.clone, @then.clone, @else.clone, @is_unless)
     end
 
-    def_equals_and_hash @cond, @then, @else
+    def_equals_and_hash @cond, @then, @else, @is_unless
   end
 
   # for inside a macro:

src/compiler/crystal/syntax/parser.cr

@@ -3505,7 +3505,7 @@ module Crystal
       end
 
       a_then, a_else = a_else, a_then if is_unless
-      MacroIf.new(cond, a_then, a_else).at_end(token_end_location)
+      MacroIf.new(cond, a_then, a_else, is_unless: is_unless).at_end(token_end_location)
     end
 
     def parse_expression_inside_macro