Fix interpolated heredoc

This fixes https://bugs.ruby-lang.org/issues/18038. The provided
reproduction showed that this happens in heredocs with double
interpolation. In this case `DSTR` was getting returned but needs to be
convered to a `EVSTR` which is what is returned by the function. There
may be an additional bug here that we weren't able to produce. It seems
odd that `STR` returns `DSTR` while everything else should return
`EVSTR` since the function is `new_evstr`.

[Bug #18038][ruby-core:104597]

Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/test/ruby/test_parse.rb b/test/ruby/test_parse.rb
index 0acbaed30f..65b8f87ad0 100644
--- a/test/ruby/test_parse.rb
+++ b/test/ruby/test_parse.rb
@@ -1080,6 +1080,32 @@ x = __ENCODING__
     end;
   end
 
+    def test_heredoc_interpolation
+      var = 1
+
+      v1 = <<~HEREDOC
+        something
+        #{"/#{var}"}
+      HEREDOC
+
+      v2 = <<~HEREDOC
+        something
+        #{other = "/#{var}"}
+      HEREDOC
+
+      v3 = <<~HEREDOC
+        something
+        #{("/#{var}")}
+      HEREDOC
+
+      assert_equal "something\n/1\n", v1
+      assert_equal "something\n/1\n", v2
+      assert_equal "something\n/1\n", v3
+      assert_equal v1, v2
+      assert_equal v2, v3
+      assert_equal v1, v3
+    end
+
   def test_unexpected_token_error
     assert_syntax_error('"x"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx', /unexpected/)
   end