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Rollup merge of rust-lang#59455 - estebank:borrow-sugg-shorthand-fiel…
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…d, r=davidtwco

Account for short-hand field syntax when suggesting borrow

Fix rust-lang#52965.
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@Centril
Centril authored Mar 30, 2019
2 parents c28704c + ddfa47f commit 41e64b6
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Showing 3 changed files with 125 additions and 20 deletions.
71 changes: 55 additions & 16 deletions src/librustc_typeck/check/demand.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -270,6 +270,26 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
None
}

fn is_hir_id_from_struct_pattern_shorthand_field(&self, hir_id: hir::HirId, sp: Span) -> bool {
let cm = self.sess().source_map();
let parent_id = self.tcx.hir().get_parent_node_by_hir_id(hir_id);
if let Some(parent) = self.tcx.hir().find_by_hir_id(parent_id) {
// Account for fields
if let Node::Expr(hir::Expr {
node: hir::ExprKind::Struct(_, fields, ..), ..
}) = parent {
if let Ok(src) = cm.span_to_snippet(sp) {
for field in fields {
if field.ident.as_str() == src.as_str() && field.is_shorthand {
return true;
}
}
}
}
}
false
}

/// This function is used to determine potential "simple" improvements or users' errors and
/// provide them useful help. For example:
///
Expand Down Expand Up @@ -299,6 +319,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
return None;
}

let is_struct_pat_shorthand_field = self.is_hir_id_from_struct_pattern_shorthand_field(
expr.hir_id,
sp,
);

match (&expected.sty, &checked_ty.sty) {
(&ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (&exp.sty, &check.sty) {
(&ty::Str, &ty::Array(arr, _)) |
Expand Down Expand Up @@ -337,12 +362,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
// bar(&x); // error, expected &mut
// ```
let ref_ty = match mutability {
hir::Mutability::MutMutable => self.tcx.mk_mut_ref(
self.tcx.mk_region(ty::ReStatic),
checked_ty),
hir::Mutability::MutImmutable => self.tcx.mk_imm_ref(
self.tcx.mk_region(ty::ReStatic),
checked_ty),
hir::Mutability::MutMutable => {
self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
}
hir::Mutability::MutImmutable => {
self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty)
}
};
if self.can_coerce(ref_ty, expected) {
if let Ok(src) = cm.span_to_snippet(sp) {
Expand All @@ -363,14 +388,22 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
if let Some(sugg) = self.can_use_as_ref(expr) {
return Some(sugg);
}
let field_name = if is_struct_pat_shorthand_field {
format!("{}: ", sugg_expr)
} else {
String::new()
};
return Some(match mutability {
hir::Mutability::MutMutable => {
(sp, "consider mutably borrowing here", format!("&mut {}",
sugg_expr))
}
hir::Mutability::MutImmutable => {
(sp, "consider borrowing here", format!("&{}", sugg_expr))
}
hir::Mutability::MutMutable => (
sp,
"consider mutably borrowing here",
format!("{}&mut {}", field_name, sugg_expr),
),
hir::Mutability::MutImmutable => (
sp,
"consider borrowing here",
format!("{}&{}", field_name, sugg_expr),
),
});
}
}
Expand Down Expand Up @@ -411,12 +444,18 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
checked,
sp) {
// do not suggest if the span comes from a macro (#52783)
if let (Ok(code),
true) = (cm.span_to_snippet(sp), sp == expr.span) {
if let (Ok(code), true) = (
cm.span_to_snippet(sp),
sp == expr.span,
) {
return Some((
sp,
"consider dereferencing the borrow",
format!("*{}", code),
if is_struct_pat_shorthand_field {
format!("{}: *{}", code, code)
} else {
format!("*{}", code)
},
));
}
}
Expand Down
18 changes: 18 additions & 0 deletions src/test/ui/deref-suggestion.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,14 @@ fn foo4(u: &u32) {
//~^ ERROR mismatched types
}

struct S<'a> {
u: &'a u32,
}

struct R {
i: u32,
}

fn main() {
let s = String::new();
let r_s = &s;
Expand All @@ -27,4 +35,14 @@ fn main() {
foo4(&0);
assert_eq!(3i32, &3i32);
//~^ ERROR mismatched types
let u = 3;
let s = S { u };
//~^ ERROR mismatched types
let s = S { u: u };
//~^ ERROR mismatched types
let i = &4;
let r = R { i };
//~^ ERROR mismatched types
let r = R { i: i };
//~^ ERROR mismatched types
}
56 changes: 52 additions & 4 deletions src/test/ui/deref-suggestion.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ LL | foo3(u);
found type `&u32`

error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:22:9
--> $DIR/deref-suggestion.rs:30:9
|
LL | foo(&"aaa".to_owned());
| ^^^^^^^^^^^^^^^^^
Expand All @@ -35,7 +35,7 @@ LL | foo(&"aaa".to_owned());
found type `&std::string::String`

error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:24:9
--> $DIR/deref-suggestion.rs:32:9
|
LL | foo(&mut "aaa".to_owned());
| ^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -59,7 +59,7 @@ LL | foo3(borrow!(0));
found type `&{integer}`

error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:28:5
--> $DIR/deref-suggestion.rs:36:5
|
LL | assert_eq!(3i32, &3i32);
| ^^^^^^^^^^^^^^^^^^^^^^^^ expected i32, found &i32
Expand All @@ -68,6 +68,54 @@ LL | assert_eq!(3i32, &3i32);
found type `&i32`
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: aborting due to 6 previous errors
error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:39:17
|
LL | let s = S { u };
| ^
| |
| expected &u32, found integer
| help: consider borrowing here: `u: &u`
|
= note: expected type `&u32`
found type `{integer}`

error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:41:20
|
LL | let s = S { u: u };
| ^
| |
| expected &u32, found integer
| help: consider borrowing here: `&u`
|
= note: expected type `&u32`
found type `{integer}`

error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:44:17
|
LL | let r = R { i };
| ^
| |
| expected u32, found &{integer}
| help: consider dereferencing the borrow: `i: *i`
|
= note: expected type `u32`
found type `&{integer}`

error[E0308]: mismatched types
--> $DIR/deref-suggestion.rs:46:20
|
LL | let r = R { i: i };
| ^
| |
| expected u32, found &{integer}
| help: consider dereferencing the borrow: `*i`
|
= note: expected type `u32`
found type `&{integer}`

error: aborting due to 10 previous errors

For more information about this error, try `rustc --explain E0308`.

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