String#+(String): don't create an extra string if either of them is e…

…mpty
crystal-lang · Jul 15, 2016 · 9df0011 · 9df0011
1 parent 38f156f
commit 9df0011
Showing 2 changed files with 15 additions and 0 deletions.
diff --git a/spec/std/string_spec.cr b/spec/std/string_spec.cr
@@ -1151,6 +1151,18 @@ describe "String" do
       str2.bytesize.should eq(8)
       str2.size.should eq(6)
     end
+
+    it "does when right is empty" do
+      str1 = "foo"
+      str2 = ""
+      (str1 + str2).should be(str1)
+    end
+
+    it "does when left is empty" do
+      str1 = ""
+      str2 = "foo"
+      (str1 + str2).should be(str2)
+    end
   end
 
   it "does %" do

diff --git a/src/string.cr b/src/string.cr
@@ -1936,6 +1936,9 @@ class String
   # "abc" + 'd'   # => "abcd"
   # ```
   def +(other : self)
+    return self if other.empty?
+    return other if self.empty?
+
     size = bytesize + other.bytesize
     String.new(size) do |buffer|
       buffer.copy_from(to_unsafe, bytesize)