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Account for short-hand field syntax when suggesting borrow #59455

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merged 4 commits into from
Mar 30, 2019
Merged

Account for short-hand field syntax when suggesting borrow #59455

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4e7ec07
Account for short-hand field syntax when suggesting borrow
estebank Mar 27, 2019
a51ca02
Expand test
estebank Mar 27, 2019
07857f7
review comments
estebank Mar 28, 2019
ddfa47f
Fix incorrect code
estebank Mar 29, 2019
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71 changes: 55 additions & 16 deletions src/librustc_typeck/check/demand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -249,6 +249,26 @@ 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 @@ -277,6 +297,11 @@ 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 @@ -315,12 +340,12 @@ 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 @@ -341,14 +366,22 @@ 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 @@ -389,12 +422,18 @@ 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
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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
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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`.