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Use more accurate return path spans 

No longer suggest `Box::new(if foo { Type1 } else { Type2 })`, instead
suggesting `if foo { Box::new(Type1) } else { Box::new(Type2) }`.
This commit is contained in:
Esteban Küber 2020-01-24 10:35:13 -08:00
parent 55dce720b2
commit d14a323e74
7 changed files with 91 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
src/librustc/traits/error_reporting/suggestions.rs
View File

@ -600,12 +600,13 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
// Visit to make sure there's a single `return` type to suggest `impl Trait`,
// otherwise suggest using `Box<dyn Trait>` or an enum.
let mut visitor = ReturnsVisitor(vec![]);
let mut visitor = ReturnsVisitor::new();
visitor.visit_body(&body);
let tables = self.in_progress_tables.map(|t| t.borrow()).unwrap();
let mut ret_types = visitor.0.iter().filter_map(|expr| tables.node_type_opt(expr.hir_id));
let mut ret_types =
visitor.returns.iter().filter_map(|expr| tables.node_type_opt(expr.hir_id));
let (last_ty, all_returns_have_same_type) = ret_types.clone().fold(
(None, true),
|(last_ty, mut same): (std::option::Option<Ty<'_>>, bool), ty| {
@ -677,7 +678,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
// Suggest `-> Box<dyn Trait>` and `Box::new(returned_value)`.
// Get all the return values and collect their span and suggestion.
let mut suggestions = visitor
.0
.returns
.iter()
.map(|expr| {
(
@ -737,10 +738,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
{
let body = hir.body(*body_id);
// Point at all the `return`s in the function as they have failed trait bounds.
let mut visitor = ReturnsVisitor(vec![]);
let mut visitor = ReturnsVisitor::new();
visitor.visit_body(&body);
let tables = self.in_progress_tables.map(|t| t.borrow()).unwrap();
for expr in &visitor.0 {
for expr in &visitor.returns {
if let Some(returned_ty) = tables.node_type_opt(expr.hir_id) {
let ty = self.resolve_vars_if_possible(&returned_ty);
err.span_label(expr.span, &format!("this returned value is of type `{}`", ty));
@ -1691,7 +1692,16 @@ pub fn suggest_constraining_type_param(
/// Collect all the returned expressions within the input expression.
/// Used to point at the return spans when we want to suggest some change to them.
struct ReturnsVisitor<'v>(Vec<&'v hir::Expr<'v>>);
struct ReturnsVisitor<'v> {
returns: Vec<&'v hir::Expr<'v>>,
in_block_tail: bool,
}
impl ReturnsVisitor<'_> {
fn new() -> Self {
ReturnsVisitor { returns: vec![], in_block_tail: false }
}
}
impl<'v> Visitor<'v> for ReturnsVisitor<'v> {
type Map = rustc::hir::map::Map<'v>;
@ -1701,20 +1711,41 @@ impl<'v> Visitor<'v> for ReturnsVisitor<'v> {
}
fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
if let hir::ExprKind::Ret(Some(ex)) = ex.kind {
self.0.push(ex);
match ex.kind {
hir::ExprKind::Ret(Some(ex)) => {
self.returns.push(ex);
}
hir::ExprKind::Block(block, _) if self.in_block_tail => {
self.in_block_tail = false;
for stmt in block.stmts {
hir::intravisit::walk_stmt(self, stmt);
}
self.in_block_tail = true;
if let Some(expr) = block.expr {
self.visit_expr(expr);
}
}
hir::ExprKind::Match(_, arms, _) if self.in_block_tail => {
for arm in arms {
self.visit_expr(arm.body);
}
}
// We need to walk to find `return`s in the entire body.
_ if !self.in_block_tail => hir::intravisit::walk_expr(self, ex),
_ => self.returns.push(ex),
}
hir::intravisit::walk_expr(self, ex);
}
fn visit_body(&mut self, body: &'v hir::Body<'v>) {
let prev = self.in_block_tail;
if body.generator_kind().is_none() {
if let hir::ExprKind::Block(block, None) = body.value.kind {
if let Some(expr) = block.expr {
self.0.push(expr);
if block.expr.is_some() {
self.in_block_tail = true;
}
}
}
hir::intravisit::walk_body(self, body);
self.in_block_tail = prev;
}
}

4
src/test/ui/error-codes/E0746.fixed
View File

@ -10,9 +10,9 @@ fn foo() -> impl Trait { Struct }
fn bar() -> impl Trait { //~ ERROR E0746
if true {
return 0;
return 0u32;
}
42
42u32
}
fn main() {}

4
src/test/ui/error-codes/E0746.rs
View File

@ -10,9 +10,9 @@ fn foo() -> dyn Trait { Struct }
fn bar() -> dyn Trait { //~ ERROR E0746
if true {
return 0;
return 0u32;
}
42
42u32
}
fn main() {}

2
src/test/ui/error-codes/E0746.stderr
View File

@ -17,7 +17,7 @@ LL | fn bar() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
help: return `impl Trait` instead, as all return paths are of type `{integer}`, which implements `Trait`
help: return `impl Trait` instead, as all return paths are of type `u32`, which implements `Trait`
|
LL | fn bar() -> impl Trait {
| ^^^^^^^^^^

11
src/test/ui/impl-trait/dyn-trait-return-should-be-impl-trait.rs
View File

@ -22,6 +22,13 @@ fn bal() -> dyn Trait { //~ ERROR E0746
}
42
}
fn bax() -> dyn Trait { //~ ERROR E0746
if true {
Struct
} else {
42
}
}
fn bam() -> Box<dyn Trait> {
if true {
return Struct; //~ ERROR mismatched types
@ -52,9 +59,9 @@ fn baw() -> Box<dyn Trait> {
// Suggest using `impl Trait`
fn bat() -> dyn Trait { //~ ERROR E0746
if true {
return 0;
return 0u32;
}
42
42u32
}
fn bay() -> dyn Trait { //~ ERROR E0746
if true {

57
src/test/ui/impl-trait/dyn-trait-return-should-be-impl-trait.stderr
View File

@ -95,8 +95,27 @@ LL | }
LL | Box::new(42)
|
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:25:13
|
LL | fn bax() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
= note: if all the returned values were of the same type you could use `impl Trait` as the return type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: you can create a new `enum` with a variant for each returned type
help: return a boxed trait object instead
|
LL | fn bax() -> Box<dyn Trait> {
LL | if true {
LL | Box::new(Struct)
LL | } else {
LL | Box::new(42)
|
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:27:16
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:34:16
|
LL | fn bam() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -112,7 +131,7 @@ LL | return Struct;
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:29:5
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:36:5
|
LL | fn bam() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -128,7 +147,7 @@ LL | 42
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:33:16
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:40:16
|
LL | fn baq() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -144,7 +163,7 @@ LL | return 0;
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:35:5
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:42:5
|
LL | fn baq() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -160,7 +179,7 @@ LL | 42
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:39:9
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:46:9
|
LL | fn baz() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -176,7 +195,7 @@ LL | Struct
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:41:9
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:48:9
|
LL | fn baz() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -192,7 +211,7 @@ LL | 42
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:46:9
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:53:9
|
LL | fn baw() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -208,7 +227,7 @@ LL | 0
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0308]: mismatched types
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:48:9
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:55:9
|
LL | fn baw() -> Box<dyn Trait> {
| -------------- expected `std::boxed::Box<(dyn Trait + 'static)>` because of return type
@ -224,38 +243,30 @@ LL | 42
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:53:13
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:60:13
|
LL | fn bat() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
help: return `impl Trait` instead, as all return paths are of type `{integer}`, which implements `Trait`
help: return `impl Trait` instead, as all return paths are of type `u32`, which implements `Trait`
|
LL | fn bat() -> impl Trait {
| ^^^^^^^^^^
error[E0746]: return type cannot have an unboxed trait object
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:59:13
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:66:13
|
LL | fn bay() -> dyn Trait {
| ^^^^^^^^^ doesn't have a size known at compile-time
|
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
= note: if all the returned values were of the same type you could use `impl Trait` as the return type
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
= note: you can create a new `enum` with a variant for each returned type
help: return a boxed trait object instead
|
LL | fn bay() -> Box<dyn Trait> {
LL | Box::new(if true {
LL | 0u32
LL | } else {
LL | 42u32
LL | })
help: return `impl Trait` instead, as all return paths are of type `u32`, which implements `Trait`
|
LL | fn bay() -> impl Trait {
| ^^^^^^^^^^
error: aborting due to 18 previous errors
error: aborting due to 19 previous errors
Some errors have detailed explanations: E0277, E0308, E0746.
For more information about an error, try `rustc --explain E0277`.

2
src/test/ui/never_type/feature-gate-never_type_fallback.stderr
View File

@ -5,7 +5,7 @@ LL | fn should_ret_unit() -> impl T {
| ^^^^^^ the trait `T` is not implemented for `()`
LL |
LL | panic!()
| -------- this returned value is of type `()`
| -------- this returned value is of type `!`
|
= note: the return type of a function must have a statically known size
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)