Added some array methods in macros: [] and length. Also: String#split with char

spec/compiler/macro/macro_expander_spec.cr

@@ -134,10 +134,14 @@ describe "MacroExpander" do
     assert_macro "", %({{"1 2 3".split}}), [] of ASTNode, %(["1", "2", "3"])
   end
 
-  it "executes string split with arguments" do
+  it "executes string split with string argument" do
     assert_macro "", %({{"1-2-3".split("-")}}), [] of ASTNode, %(["1", "2", "3"])
   end
 
+  it "executes string split with char argument" do
+    assert_macro "", %({{"1-2-3".split('-')}}), [] of ASTNode, %(["1", "2", "3"])
+  end
+
   it "executes string strip" do
     assert_macro "", %({{"  hello   ".strip}}), [] of ASTNode, "hello"
   end
@@ -153,4 +157,16 @@ describe "MacroExpander" do
   it "executes string lines" do
     assert_macro "x", %({{x.lines}}), [StringLiteral.new("1\n2\n3")] of ASTNode, %(["1", "2", "3"])
   end
+
+  it "executes array index 0" do
+    assert_macro "", %({{[1, 2, 3][0]}}), [] of ASTNode, "1"
+  end
+
+  it "executes array index 1" do
+    assert_macro "", %({{[1, 2, 3][1]}}), [] of ASTNode, "2"
+  end
+
+  it "executes array length" do
+    assert_macro "", %({{[1, 2, 3].length}}), [] of ASTNode, "3"
+  end
 end

src/compiler/crystal/macro_expander.cr

@@ -304,7 +304,12 @@ module Crystal
         when 0
           create_array_literal_from_values(@value.split)
         when 1
-          create_array_literal_from_values(@value.split(args.first.to_macro_id))
+          first_arg = args.first
+          if first_arg.is_a?(CharLiteral)
+            create_array_literal_from_values(@value.split(first_arg.value))
+          else
+            create_array_literal_from_values(@value.split(first_arg.to_macro_id))
+          end
         else
           raise "wrong number of arguments for split (#{args.length} for 0, 1)"
         end
@@ -322,6 +327,35 @@ module Crystal
     end
   end
 
+  class ArrayLiteral
+    def interpret(method, args)
+      case method
+      when "length"
+        interpret_argumentless_method(method, args) { NumberLiteral.new(elements.length, :i32) }
+      when "[]"
+        case args.length
+        when 1
+          arg = args.first
+          unless arg.is_a?(NumberLiteral)
+            arg.raise "argument to [] must be a number, not #{arg}"
+          end
+
+          index = arg.to_number.to_i
+          value = elements[index]?
+          if value
+            value
+          else
+            raise "array index out of bounds: #{index} in #{self}"
+          end
+        else
+          raise "wrong number of arguments for [] (#{args.length} for 1)"
+        end
+      else
+        super
+      end
+    end
+  end
+
   class SymbolLiteral
     def to_macro_id
       @value