MatchData: raise KeyError instead of ArgumentError

makenowjust · asterite · commit 5fb043897b46 · 2017-06-12T13:25:00.000-03:00
Currently #[](key: String) raises `ArgumentError`. I think it should
raise `KeyError` because it looks like `Hash` operation.
diff --git a/spec/std/match_data_spec.cr b/spec/std/match_data_spec.cr
@@ -34,7 +34,7 @@ describe "Regex::MatchData" do
 
     it "raises exception when named group doesn't exist" do
       ("foo" =~ /foo/).should eq(0)
-      expect_raises(ArgumentError) { $~["group"] }
+      expect_raises(KeyError) { $~["group"] }
     end
 
     it "raises if outside match range with []" do
diff --git a/src/regex/match_data.cr b/src/regex/match_data.cr
@@ -148,16 +148,16 @@ class Regex
     end
 
     # Returns the match of the capture group named by *group_name*, or
-    # raises an `ArgumentError` if there is no such named capture group.
+    # raises an `KeyError` if there is no such named capture group.
     #
     # ```
     # "Crystal".match(/r(?<ok>ys)/).not_nil!["ok"] # => "ys"
-    # "Crystal".match(/r(?<ok>ys)/).not_nil!["ng"] # raises ArgumentError
+    # "Crystal".match(/r(?<ok>ys)/).not_nil!["ng"] # raises KeyError
     # ```
     def [](group_name : String)
       match = self[group_name]?
       unless match
-        raise ArgumentError.new("Match group named '#{group_name}' does not exist")
+        raise KeyError.new("Match group named '#{group_name}' does not exist")
       end
       match
     end
