From: Esteban Küber <esteban@kuber.com.ar>
Date: Fri, 17 May 2019 17:45:54 +0000 (-0700)
Subject: Account for &String + String
X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;h=8895fb945d0ea0ce124923aadc16adb68c74f3e6;p=rust.git

Account for &String + String
---

diff --git a/src/librustc_typeck/check/op.rs b/src/librustc_typeck/check/op.rs
index 26a5bdfef7d..cd207478f8f 100644
--- a/src/librustc_typeck/check/op.rs
+++ b/src/librustc_typeck/check/op.rs
@@ -579,10 +579,17 @@ fn check_str_addition(
                     is_assign,
                 ) {
                     (Ok(l), Ok(r), false) => {
+                        let to_string = if l.starts_with("&") {
+                            // let a = String::new(); let b = String::new();
+                            // let _ = &a + b;
+                            format!("{}", &l[1..])
+                        } else {
+                            format!("{}.to_owned()", l)
+                        };
                         err.multipart_suggestion(
                             msg,
                             vec![
-                                (lhs_expr.span, format!("{}.to_owned()", l)),
+                                (lhs_expr.span, to_string),
                                 (rhs_expr.span, format!("&{}", r)),
                             ],
                             Applicability::MachineApplicable,
diff --git a/src/test/ui/span/issue-39018.stderr b/src/test/ui/span/issue-39018.stderr
index cdb9c1168d8..d8fbf841b61 100644
--- a/src/test/ui/span/issue-39018.stderr
+++ b/src/test/ui/span/issue-39018.stderr
@@ -57,8 +57,8 @@ LL |     let _ = &a + b;
    |             &std::string::String
 help: `to_owned()` can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left
    |
-LL |     let _ = &a.to_owned() + &b;
-   |             ^^^^^^^^^^^^^   ^^
+LL |     let _ = a + &b;
+   |             ^   ^^
 
 error[E0308]: mismatched types
   --> $DIR/issue-39018.rs:29:17