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Handle more string addition cases with appropriate suggestions

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This commit is contained in:
Esteban Küber 2019-05-16 19:29:02 -07:00
parent 1962adea6a
commit 234adf84bd
4 changed files with 209 additions and 18 deletions
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57
src/librustc_typeck/check/op.rs
View file

@ -502,6 +502,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
false
}
/// Provide actionable suggestions when trying to add two strings with incorrect types,
/// like `&str + &str`, `String + String` and `&str + &String`.
///
/// If this function returns `true` it means a note was printed, so we don't need
/// to print the normal "implementation of `std::ops::Add` might be missing" note
fn check_str_addition(
&self,
expr: &'gcx hir::Expr,
@ -514,33 +519,57 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
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";
// If this function returns true it means a note was printed, so we don't need
// to print the normal "implementation of `std::ops::Add` might be missing" note
debug!("check_str_addition: {:?} + {:?}", lhs_ty, rhs_ty);
match (&lhs_ty.sty, &rhs_ty.sty) {
(&Ref(_, l_ty, _), &Ref(_, r_ty, _))
if l_ty.sty == Str && r_ty.sty == Str => {
(&Ref(_, l_ty, _), &Ref(_, r_ty, _)) // &str or &String + &str, &String or &&str
if (l_ty.sty == Str || &format!("{:?}", l_ty) == "std::string::String") && (
r_ty.sty == Str ||
&format!("{:?}", r_ty) == "std::string::String" ||
&format!("{:?}", rhs_ty) == "&&str"
) =>
{
if !is_assign {
err.span_label(op.span,
"`+` can't be used to concatenate two `&str` strings");
err.span_label(
op.span,
"`+` can't be used to concatenate two `&str` strings",
);
match source_map.span_to_snippet(lhs_expr.span) {
Ok(lstring) => err.span_suggestion(
lhs_expr.span,
msg,
format!("{}.to_owned()", lstring),
Applicability::MachineApplicable,
),
Ok(lstring) => {
err.span_suggestion(
lhs_expr.span,
if lstring.starts_with("&") {
remove_borrow_msg
} else {
msg
},
if lstring.starts_with("&") {
// let a = String::new();
// let _ = &a + "bar";
format!("{}", &lstring[1..])
} else {
format!("{}.to_owned()", lstring)
},
Applicability::MachineApplicable,
)
}
_ => err.help(msg),
};
}
true
}
(&Ref(_, l_ty, _), &Adt(..))
if l_ty.sty == Str && &format!("{:?}", rhs_ty) == "std::string::String" => {
(&Ref(_, l_ty, _), &Adt(..)) // Handle `&str` & `&String` + `String`
if (l_ty.sty == Str || &format!("{:?}", l_ty) == "std::string::String") &&
&format!("{:?}", rhs_ty) == "std::string::String" =>
{
err.span_label(expr.span,
"`+` can't be used to concatenate a `&str` with a `String`");
match (

20
src/test/ui/span/issue-39018.rs
View file

@ -16,3 +16,23 @@ enum World {
Hello,
Goodbye,
}
fn foo() {
let a = String::new();
let b = String::new();
let c = "";
let d = "";
let e = &a;
let _ = &a + &b; //~ ERROR binary operation
let _ = &a + b; //~ ERROR binary operation
let _ = a + &b; // ok
let _ = a + b; //~ ERROR mismatched types
let _ = e + b; //~ ERROR binary operation
let _ = e + &b; //~ ERROR binary operation
let _ = e + d; //~ ERROR binary operation
let _ = e + &d; //~ ERROR binary operation
let _ = &c + &d; //~ ERROR binary operation
let _ = &c + d; //~ ERROR binary operation
let _ = c + &d; //~ ERROR binary operation
let _ = c + d; //~ ERROR binary operation
}

143
src/test/ui/span/issue-39018.stderr
View file

@ -35,6 +35,145 @@ help: `to_owned()` can be used to create an owned `String` from a string referen
LL | let x = "Hello ".to_owned() + &"World!".to_owned();
| ^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^
error: aborting due to 3 previous errors
error[E0369]: binary operation `+` cannot be applied to type `&std::string::String`
--> $DIR/issue-39018.rs:26:16
|
LL | let _ = &a + &b;
| -- ^ -- &std::string::String
| | |
| | `+` can't be used to concatenate two `&str` strings
| &std::string::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
|
LL | let _ = a + &b;
| ^
For more information about this error, try `rustc --explain E0369`.
error[E0369]: binary operation `+` cannot be applied to type `&std::string::String`
--> $DIR/issue-39018.rs:27:16
|
LL | let _ = &a + b;
| ---^--
| | |
| | std::string::String
| &std::string::String
| `+` can't be used to concatenate a `&str` with a `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;
| ^^^^^^^^^^^^^ ^^
error[E0308]: mismatched types
--> $DIR/issue-39018.rs:29:17
|
LL | let _ = a + b;
| ^
| |
| expected &str, found struct `std::string::String`
| help: consider borrowing here: `&b`
|
= note: expected type `&str`
found type `std::string::String`
error[E0369]: binary operation `+` cannot be applied to type `&std::string::String`
--> $DIR/issue-39018.rs:30:15
|
LL | let _ = e + b;
| --^--
| | |
| | std::string::String
| &std::string::String
| `+` can't be used to concatenate a `&str` with a `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 _ = e.to_owned() + &b;
| ^^^^^^^^^^^^ ^^
error[E0369]: binary operation `+` cannot be applied to type `&std::string::String`
--> $DIR/issue-39018.rs:31:15
|
LL | let _ = e + &b;
| - ^ -- &std::string::String
| | |
| | `+` can't be used to concatenate two `&str` strings
| &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 _ = e.to_owned() + &b;
| ^^^^^^^^^^^^
error[E0369]: binary operation `+` cannot be applied to type `&std::string::String`
--> $DIR/issue-39018.rs:32:15
|
LL | let _ = e + d;
| - ^ - &str
| | |
| | `+` can't be used to concatenate two `&str` strings
| &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 _ = e.to_owned() + d;
| ^^^^^^^^^^^^
error[E0369]: binary operation `+` cannot be applied to type `&std::string::String`
--> $DIR/issue-39018.rs:33:15
|
LL | let _ = e + &d;
| - ^ -- &&str
| | |
| | `+` can't be used to concatenate two `&str` strings
| &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 _ = e.to_owned() + &d;
| ^^^^^^^^^^^^
error[E0369]: binary operation `+` cannot be applied to type `&&str`
--> $DIR/issue-39018.rs:34:16
|
LL | let _ = &c + &d;
| -- ^ -- &&str
| |
| &&str
|
= note: an implementation of `std::ops::Add` might be missing for `&&str`
error[E0369]: binary operation `+` cannot be applied to type `&&str`
--> $DIR/issue-39018.rs:35:16
|
LL | let _ = &c + d;
| -- ^ - &str
| |
| &&str
|
= note: an implementation of `std::ops::Add` might be missing for `&&str`
error[E0369]: binary operation `+` cannot be applied to type `&str`
--> $DIR/issue-39018.rs:36:15
|
LL | let _ = c + &d;
| - ^ -- &&str
| | |
| | `+` can't 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
|
LL | let _ = c.to_owned() + &d;
| ^^^^^^^^^^^^
error[E0369]: binary operation `+` cannot be applied to type `&str`
--> $DIR/issue-39018.rs:37:15
|
LL | let _ = c + d;
| - ^ - &str
| | |
| | `+` can't 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
|
LL | let _ = c.to_owned() + d;
| ^^^^^^^^^^^^
error: aborting due to 14 previous errors
Some errors have detailed explanations: E0308, E0369.
For more information about an error, try `rustc --explain E0308`.

7
src/test/ui/str/str-concat-on-double-ref.stderr
View file

@ -3,10 +3,13 @@ error[E0369]: binary operation `+` cannot be applied to type `&std::string::Stri
|
LL | let c = a + b;
| - ^ - &str
| |
| | |
| | `+` can't be used to concatenate two `&str` strings
| &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
|
= note: an implementation of `std::ops::Add` might be missing for `&std::string::String`
LL | let c = a.to_owned() + b;
| ^^^^^^^^^^^^
error: aborting due to previous error