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Rollup merge of #92843 - camelid:str-concat-sugg, r=davidtwco

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Improve string concatenation suggestion

Before:

    error[E0369]: cannot add `&str` to `&str`
     --> file.rs:2:22
      |
    2 |     let _x = "hello" + " world";
      |              ------- ^ -------- &str
      |              |       |
      |              |       `+` cannot be used to concatenate two `&str` strings
      |              &str
      |
    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
      |
    2 |     let _x = "hello".to_owned() + " world";
      |              ~~~~~~~~~~~~~~~~~~

After:

    error[E0369]: cannot add `&str` to `&str`
     --> file.rs:2:22
      |
    2 |     let _x = "hello" + " world";
      |              ------- ^ -------- &str
      |              |       |
      |              |       `+` cannot be used to concatenate two `&str` strings
      |              &str
      |
      = note: string concatenation requires an owned `String` on the left
    help: create an owned `String` from a string reference
      |
    2 |     let _x = "hello".to_owned() + " world";
      |                     +++++++++++
This commit is contained in:
Matthias Krüger 2022-01-21 22:03:15 +01:00 committed by GitHub
commit 430673f265
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 81 additions and 85 deletions
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93
compiler/rustc_typeck/src/check/op.rs
View File

@ -549,16 +549,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
is_assign: IsAssign,
op: hir::BinOp,
) -> bool {
let source_map = self.tcx.sess.source_map();
let remove_borrow_msg = "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";
let msg = "`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";
let str_concat_note = "string concatenation requires an owned `String` on the left";
let rm_borrow_msg = "remove the borrow to obtain an owned `String`";
let to_owned_msg = "create an owned `String` from a string reference";
let string_type = self.tcx.get_diagnostic_item(sym::String);
let is_std_string = |ty: Ty<'tcx>| match ty.ty_adt_def() {
@ -574,31 +567,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
) =>
{
if let IsAssign::No = is_assign { // Do not supply this message if `&str += &str`
err.span_label(
op.span,
"`+` cannot be used to concatenate two `&str` strings",
);
match source_map.span_to_snippet(lhs_expr.span) {
Ok(lstring) => {
err.span_suggestion(
lhs_expr.span,
if lstring.starts_with('&') {
remove_borrow_msg
} else {
msg
},
if let Some(stripped) = lstring.strip_prefix('&') {
// let a = String::new();
// let _ = &a + "bar";
stripped.to_string()
} else {
format!("{}.to_owned()", lstring)
},
Applicability::MachineApplicable,
)
}
_ => err.help(msg),
};
err.span_label(op.span, "`+` cannot be used to concatenate two `&str` strings");
err.note(str_concat_note);
if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
err.span_suggestion_verbose(
lhs_expr.span.until(lhs_inner_expr.span),
rm_borrow_msg,
"".to_owned(),
Applicability::MachineApplicable
);
} else {
err.span_suggestion_verbose(
lhs_expr.span.shrink_to_hi(),
to_owned_msg,
".to_owned()".to_owned(),
Applicability::MachineApplicable
);
}
}
true
}
@ -609,32 +594,30 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
op.span,
"`+` cannot be used to concatenate a `&str` with a `String`",
);
match (
source_map.span_to_snippet(lhs_expr.span),
source_map.span_to_snippet(rhs_expr.span),
is_assign,
) {
(Ok(l), Ok(r), IsAssign::No) => {
let to_string = if let Some(stripped) = l.strip_prefix('&') {
// let a = String::new(); let b = String::new();
// let _ = &a + b;
stripped.to_string()
match is_assign {
IsAssign::No => {
let sugg_msg;
let lhs_sugg = if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
sugg_msg = "remove the borrow on the left and add one on the right";
(lhs_expr.span.until(lhs_inner_expr.span), "".to_owned())
} else {
format!("{}.to_owned()", l)
sugg_msg = "create an owned `String` on the left and add a borrow on the right";
(lhs_expr.span.shrink_to_hi(), ".to_owned()".to_owned())
};
err.multipart_suggestion(
msg,
vec![
(lhs_expr.span, to_string),
(rhs_expr.span, format!("&{}", r)),
],
let suggestions = vec![
lhs_sugg,
(rhs_expr.span.shrink_to_lo(), "&".to_owned()),
];
err.multipart_suggestion_verbose(
sugg_msg,
suggestions,
Applicability::MachineApplicable,
);
}
_ => {
err.help(msg);
IsAssign::Yes => {
err.note(str_concat_note);
}
};
}
true
}
_ => false,

5
src/test/ui/issues/issue-47377.stderr
View File

@ -7,10 +7,11 @@ LL | let _a = b + ", World!";
| | `+` cannot be used to concatenate two `&str` strings
| &str
|
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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _a = b.to_owned() + ", World!";
| ~~~~~~~~~~~~
| +++++++++++
error: aborting due to previous error

5
src/test/ui/issues/issue-47380.stderr
View File

@ -7,10 +7,11 @@ LL | println!("🦀🦀🦀🦀🦀"); let _a = b + ", World!";
| | `+` cannot be used to concatenate two `&str` strings
| &str
|
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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | println!("🦀🦀🦀🦀🦀"); let _a = b.to_owned() + ", World!";
| ~~~~~~~~~~~~
| +++++++++++
error: aborting due to previous error

53
src/test/ui/span/issue-39018.stderr
View File

@ -7,10 +7,11 @@ LL | let x = "Hello " + "World!";
| | `+` cannot be used to concatenate two `&str` strings
| &str
|
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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let x = "Hello ".to_owned() + "World!";
| ~~~~~~~~~~~~~~~~~~~
| +++++++++++
error[E0369]: cannot add `World` to `World`
--> $DIR/issue-39018.rs:8:26
@ -46,10 +47,10 @@ LL | let x = "Hello " + "World!".to_owned();
| | `+` cannot be used to concatenate a `&str` with a `String`
| &str
|
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
help: create an owned `String` on the left and add a borrow on the right
|
LL | let x = "Hello ".to_owned() + &"World!".to_owned();
| ~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~
| +++++++++++ +
error[E0369]: cannot add `&String` to `&String`
--> $DIR/issue-39018.rs:26:16
@ -60,10 +61,12 @@ LL | let _ = &a + &b;
| | `+` cannot be used to concatenate two `&str` strings
| &String
|
help: 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
= note: string concatenation requires an owned `String` on the left
help: remove the borrow to obtain an owned `String`
|
LL | let _ = a + &b;
| ~
LL - let _ = &a + &b;
LL + let _ = a + &b;
|
error[E0369]: cannot add `String` to `&String`
--> $DIR/issue-39018.rs:27:16
@ -74,10 +77,11 @@ LL | let _ = &a + b;
| | `+` cannot be used to concatenate a `&str` with a `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
help: remove the borrow on the left and add one on the right
|
LL | let _ = a + &b;
| ~ ~~
LL - let _ = &a + b;
LL + let _ = a + &b;
|
error[E0308]: mismatched types
--> $DIR/issue-39018.rs:29:17
@ -97,10 +101,10 @@ LL | let _ = e + b;
| | `+` cannot be used to concatenate a `&str` with a `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
help: create an owned `String` on the left and add a borrow on the right
|
LL | let _ = e.to_owned() + &b;
| ~~~~~~~~~~~~ ~~
| +++++++++++ +
error[E0369]: cannot add `&String` to `&String`
--> $DIR/issue-39018.rs:31:15
@ -111,10 +115,11 @@ LL | let _ = e + &b;
| | `+` cannot be used to concatenate two `&str` strings
| &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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _ = e.to_owned() + &b;
| ~~~~~~~~~~~~
| +++++++++++
error[E0369]: cannot add `&str` to `&String`
--> $DIR/issue-39018.rs:32:15
@ -125,10 +130,11 @@ LL | let _ = e + d;
| | `+` cannot be used to concatenate two `&str` strings
| &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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _ = e.to_owned() + d;
| ~~~~~~~~~~~~
| +++++++++++
error[E0369]: cannot add `&&str` to `&String`
--> $DIR/issue-39018.rs:33:15
@ -139,10 +145,11 @@ LL | let _ = e + &d;
| | `+` cannot be used to concatenate two `&str` strings
| &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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _ = e.to_owned() + &d;
| ~~~~~~~~~~~~
| +++++++++++
error[E0369]: cannot add `&&str` to `&&str`
--> $DIR/issue-39018.rs:34:16
@ -169,10 +176,11 @@ LL | let _ = c + &d;
| | `+` cannot be used to concatenate two `&str` strings
| &str
|
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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _ = c.to_owned() + &d;
| ~~~~~~~~~~~~
| +++++++++++
error[E0369]: cannot add `&str` to `&str`
--> $DIR/issue-39018.rs:37:15
@ -183,10 +191,11 @@ LL | let _ = c + d;
| | `+` cannot be used to concatenate two `&str` strings
| &str
|
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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _ = c.to_owned() + d;
| ~~~~~~~~~~~~
| +++++++++++
error: aborting due to 14 previous errors

5
src/test/ui/str/str-concat-on-double-ref.stderr
View File

@ -7,10 +7,11 @@ LL | let c = a + b;
| | `+` cannot be used to concatenate two `&str` strings
| &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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let c = a.to_owned() + b;
| ~~~~~~~~~~~~
| +++++++++++
error: aborting due to previous error

5
src/test/ui/terminal-width/non-1-width-unicode-multiline-label.stderr
View File

@ -7,10 +7,11 @@ LL | ...ཽཾཿ྄ཱྀྀྂྃ྅྆྇ྈྉྊྋྌྍྎྏྐྑྒྒྷྔ
| | `+` cannot be used to concatenate two `&str` strings
| &str
|
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
= note: string concatenation requires an owned `String` on the left
help: create an owned `String` from a string reference
|
LL | let _ = "ༀ༁༂༃༄༅༆༇༈༉༊་༌།༎༏༐༑༒༓༔༕༖༗༘༙༚༛༜༝༞༟༠༡༢༣༤༥༦༧༨༩༪༫༬༭༮༯༰༱༲༳༴༵༶༷༸༹༺༻༼༽༾༿ཀཁགགྷངཅཆཇ཈ཉཊཋཌཌྷཎཏཐདདྷནཔཕབབྷམཙཚཛཛྷཝཞཟའཡརལཤཥསཧཨཀྵཪཫཬ཭཮཯཰ཱཱཱིིུུྲྀཷླྀཹེཻོཽཾཿ྄ཱྀྀྂྃ྅྆྇ྈྉྊྋྌྍྎྏྐྑྒྒྷྔྕྖྗ྘ྙྚྛྜྜྷྞྟྠྡྡྷྣྤྥྦྦྷྨྩྪྫྫྷྭྮྯྰྱྲླྴྵྶྷྸྐྵྺྻྼ྽྾྿࿀࿁࿂࿃࿄࿅࿆࿇࿈࿉࿊࿋࿌࿍࿎࿏࿐࿑࿒࿓࿔࿕࿖࿗࿘࿙࿚"; let _a = unicode_is_fun.to_owned() + " really fun!";
| ~~~~~~~~~~~~~~~~~~~~~~~~~
| +++++++++++
error: aborting due to previous error