Pasting text adds "\" character

When I have a text and I paste it to another, it adds unnecessary "\" characters.
Example:
` String paste = "paste";
String test = "example" + "text";`
Copy "paste" over " + " to make `"example"paste"text"`, it should create `"examplepastetext"` text, but it's `"example\"paste\"text"`

Reproduce the issue in Eclipse JDT UI using the Java snippets and the described paste operation, then trace the editor's paste handling to find where the extra backslashes are introduced. Done means copying the string content over the concatenation operator produces examplepastetext without added backslashes, with the behavior covered by a regression test.

Written by the indexing model from the issue text.