Added $1?, $2?, etc. as a nilable alternative to$1, $2

Author: Ary Borenszweig

spec/compiler/lexer/lexer_spec.cr

@@ -114,7 +114,7 @@ end
 
 private def it_lexes_global_match_data_index(globals)
   globals.each do |global|
-    it_lexes global, :GLOBAL_MATCH_DATA_INDEX, global[1, global.length - 1].to_i
+    it_lexes global, :GLOBAL_MATCH_DATA_INDEX, global[1, global.length - 1]
   end
 end
 
@@ -234,7 +234,7 @@ describe "Lexer" do
   it_lexes_symbols [":foo", ":foo!", ":foo?", ":\"foo\"", ":かたな", ":+", ":-", ":*", ":/",
                     ":==", ":<", ":<=", ":>", ":>=", ":!", ":!=", ":=~", ":!~", ":&", ":|",
                     ":^", ":~", ":**", ":>>", ":<<", ":%", ":[]", ":[]?", ":[]=", ":<=>", ":==="]
-  it_lexes_global_match_data_index ["$1", "$10"]
+  it_lexes_global_match_data_index ["$1", "$10", "$1?", "$23?"]
 
   it_lexes "$~", :"$~"
   it_lexes "$?", :"$?"

spec/compiler/parser/parser_spec.cr

@@ -754,6 +754,7 @@ describe "Parser" do
   it_parses "$~", Call.new("$~".var, "not_nil!")
   it_parses "$~.foo", Call.new(Call.new("$~".var, "not_nil!"), "foo")
   it_parses "$1", Call.new(Call.new("$~".var, "not_nil!"), "[]", 1.int32)
+  it_parses "$1?", Call.new(Call.new("$~".var, "not_nil!"), "[]?", 1.int32)
   it_parses "foo $1", Call.new(nil, "foo", Call.new(Call.new("$~".var, "not_nil!"), "[]", 1.int32))
   it_parses "$~ = 1", Assign.new("$~".var, 1.int32)
 

src/compiler/crystal/syntax/lexer.cr

@@ -586,13 +586,18 @@ module Crystal
           next_char
           @token.type = :"$?"
         when .digit?
-          number = current_char - '0'
-          while (char = next_char).digit?
-            number *= 10
-            number += char - '0'
+          start = current_pos
+          char = next_char
+          if char == '0'
+            char = next_char
+          else
+            while char.digit?
+              char = next_char
+            end
+            char = next_char if char == '?'
           end
           @token.type = :GLOBAL_MATCH_DATA_INDEX
-          @token.value = number
+          @token.value = string_range(start)
         else
           if ident_start?(current_char)
             while ident_part?(next_char)

src/compiler/crystal/syntax/parser.cr

@@ -808,12 +808,18 @@ module Crystal
           node_and_next_token Call.new(var, "not_nil!").at(location)
         end
       when :GLOBAL_MATCH_DATA_INDEX
-        value = @token.value
-        if value == 0
+        value = @token.value.to_s
+        if value == "0"
           node_and_next_token Path.global("PROGRAM_NAME")
         else
+          if value.ends_with? '?'
+            method = "[]?"
+            value = value.chop
+          else
+            method = "[]"
+          end
           location = @token.location
-          node_and_next_token Call.new(Call.new(Var.new("$~").at(location), "not_nil!").at(location), "[]", NumberLiteral.new(value as Int32))
+          node_and_next_token Call.new(Call.new(Var.new("$~").at(location), "not_nil!").at(location), method, NumberLiteral.new(value.to_i))
         end
       when :__LINE__
         node_and_next_token MagicConstant.expand_line_node(@token.location)