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Rollup merge of #99539 - compiler-errors:bidirectional-block-suggestions, r=fee1-dead

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Improve suggestions for returning binding

Fixes #99525

Also reworks the cause codes for match and if a bit, I think cleaning them up in a positive way.
We no longer need to call `could_remove_semicolon` in successful code, which might save a few cycles?
This commit is contained in:
Dylan DPC 2022-07-22 11:53:42 +05:30 • committed by GitHub
commit 92bebac0b9
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13 changed files with 625 additions and 467 deletions
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10
compiler/rustc_hir/src/hir.rs
View file

@ -954,6 +954,16 @@ pub struct Block<'hir> {
pub targeted_by_break: bool,
}
impl<'hir> Block<'hir> {
pub fn innermost_block(&self) -> &Block<'hir> {
let mut block = self;
while let Some(Expr { kind: ExprKind::Block(inner_block, _), .. }) = block.expr {
block = inner_block;
}
block
}
}
#[derive(Debug, HashStable_Generic)]
pub struct Pat<'hir> {
#[stable_hasher(ignore)]

539
compiler/rustc_infer/src/infer/error_reporting/mod.rs
View file

@ -316,37 +316,6 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
err
}
/// Structurally compares two types, modulo any inference variables.
///
/// Returns `true` if two types are equal, or if one type is an inference variable compatible
/// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
/// FloatVar inference type are compatible with themselves or their concrete types (Int and
/// Float types, respectively). When comparing two ADTs, these rules apply recursively.
pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
match (&a.kind(), &b.kind()) {
(&ty::Adt(did_a, substs_a), &ty::Adt(did_b, substs_b)) => {
if did_a != did_b {
return false;
}
substs_a.types().zip(substs_b.types()).all(|(a, b)| same_type_modulo_infer(a, b))
}
(&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
| (&ty::Infer(ty::InferTy::IntVar(_)), &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)))
| (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
| (
&ty::Infer(ty::InferTy::FloatVar(_)),
&ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
)
| (&ty::Infer(ty::InferTy::TyVar(_)), _)
| (_, &ty::Infer(ty::InferTy::TyVar(_))) => true,
(&ty::Ref(_, ty_a, mut_a), &ty::Ref(_, ty_b, mut_b)) => {
mut_a == mut_b && same_type_modulo_infer(*ty_a, *ty_b)
}
_ => a == b,
}
}
impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
pub fn report_region_errors(
&self,
@ -645,13 +614,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
err.span_label(span, "expected due to this");
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
semi_span,
arm_block_id,
arm_span,
arm_ty,
prior_arm_block_id,
prior_arm_span,
prior_arm_ty,
source,
ref prior_arms,
last_ty,
scrut_hir_id,
opt_suggest_box_span,
arm_span,
scrut_span,
..
}) => match source {
@ -682,10 +654,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
}
_ => {
// `last_ty` can be `!`, `expected` will have better info when present.
// `prior_arm_ty` can be `!`, `expected` will have better info when present.
let t = self.resolve_vars_if_possible(match exp_found {
Some(ty::error::ExpectedFound { expected, .. }) => expected,
_ => last_ty,
_ => prior_arm_ty,
});
let source_map = self.tcx.sess.source_map();
let mut any_multiline_arm = source_map.is_multiline(arm_span);
@ -710,37 +682,15 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
};
let msg = "`match` arms have incompatible types";
err.span_label(outer_error_span, msg);
if let Some((sp, boxed)) = semi_span {
if let (StatementAsExpression::NeedsBoxing, [.., prior_arm]) =
(boxed, &prior_arms[..])
{
err.multipart_suggestion(
"consider removing this semicolon and boxing the expressions",
vec![
(prior_arm.shrink_to_lo(), "Box::new(".to_string()),
(prior_arm.shrink_to_hi(), ")".to_string()),
(arm_span.shrink_to_lo(), "Box::new(".to_string()),
(arm_span.shrink_to_hi(), ")".to_string()),
(sp, String::new()),
],
Applicability::HasPlaceholders,
);
} else if matches!(boxed, StatementAsExpression::NeedsBoxing) {
err.span_suggestion_short(
sp,
"consider removing this semicolon and boxing the expressions",
"",
Applicability::MachineApplicable,
);
} else {
err.span_suggestion_short(
sp,
"consider removing this semicolon",
"",
Applicability::MachineApplicable,
);
}
}
self.suggest_remove_semi_or_return_binding(
err,
prior_arm_block_id,
prior_arm_ty,
prior_arm_span,
arm_block_id,
arm_ty,
arm_span,
);
if let Some(ret_sp) = opt_suggest_box_span {
// Get return type span and point to it.
self.suggest_boxing_for_return_impl_trait(
@ -752,43 +702,33 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
},
ObligationCauseCode::IfExpression(box IfExpressionCause {
then,
else_sp,
outer,
semicolon,
then_id,
else_id,
then_ty,
else_ty,
outer_span,
opt_suggest_box_span,
}) => {
err.span_label(then, "expected because of this");
if let Some(sp) = outer {
let then_span = self.find_block_span_from_hir_id(then_id);
let else_span = self.find_block_span_from_hir_id(then_id);
err.span_label(then_span, "expected because of this");
if let Some(sp) = outer_span {
err.span_label(sp, "`if` and `else` have incompatible types");
}
if let Some((sp, boxed)) = semicolon {
if matches!(boxed, StatementAsExpression::NeedsBoxing) {
err.multipart_suggestion(
"consider removing this semicolon and boxing the expression",
vec![
(then.shrink_to_lo(), "Box::new(".to_string()),
(then.shrink_to_hi(), ")".to_string()),
(else_sp.shrink_to_lo(), "Box::new(".to_string()),
(else_sp.shrink_to_hi(), ")".to_string()),
(sp, String::new()),
],
Applicability::MachineApplicable,
);
} else {
err.span_suggestion_short(
sp,
"consider removing this semicolon",
"",
Applicability::MachineApplicable,
);
}
}
self.suggest_remove_semi_or_return_binding(
err,
Some(then_id),
then_ty,
then_span,
Some(else_id),
else_ty,
else_span,
);
if let Some(ret_sp) = opt_suggest_box_span {
self.suggest_boxing_for_return_impl_trait(
err,
ret_sp,
[then, else_sp].into_iter(),
[then_span, else_span].into_iter(),
);
}
}
@ -808,6 +748,56 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
}
fn suggest_remove_semi_or_return_binding(
&self,
err: &mut Diagnostic,
first_id: Option<hir::HirId>,
first_ty: Ty<'tcx>,
first_span: Span,
second_id: Option<hir::HirId>,
second_ty: Ty<'tcx>,
second_span: Span,
) {
let remove_semicolon =
[(first_id, second_ty), (second_id, first_ty)].into_iter().find_map(|(id, ty)| {
let hir::Node::Block(blk) = self.tcx.hir().get(id?) else { return None };
self.could_remove_semicolon(blk, ty)
});
match remove_semicolon {
Some((sp, StatementAsExpression::NeedsBoxing)) => {
err.multipart_suggestion(
"consider removing this semicolon and boxing the expressions",
vec![
(first_span.shrink_to_lo(), "Box::new(".to_string()),
(first_span.shrink_to_hi(), ")".to_string()),
(second_span.shrink_to_lo(), "Box::new(".to_string()),
(second_span.shrink_to_hi(), ")".to_string()),
(sp, String::new()),
],
Applicability::MachineApplicable,
);
}
Some((sp, StatementAsExpression::CorrectType)) => {
err.span_suggestion_short(
sp,
"consider removing this semicolon",
"",
Applicability::MachineApplicable,
);
}
None => {
for (id, ty) in [(first_id, second_ty), (second_id, first_ty)] {
if let Some(id) = id
&& let hir::Node::Block(blk) = self.tcx.hir().get(id)
&& self.consider_returning_binding(blk, ty, err)
{
break;
}
}
}
}
}
fn suggest_boxing_for_return_impl_trait(
&self,
err: &mut Diagnostic,
@ -1723,15 +1713,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
};
debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
if let Some(exp_found) = exp_found {
let should_suggest_fixes = if let ObligationCauseCode::Pattern { root_ty, .. } =
cause.code()
{
// Skip if the root_ty of the pattern is not the same as the expected_ty.
// If these types aren't equal then we've probably peeled off a layer of arrays.
same_type_modulo_infer(self.resolve_vars_if_possible(*root_ty), exp_found.expected)
} else {
true
};
let should_suggest_fixes =
if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
// Skip if the root_ty of the pattern is not the same as the expected_ty.
// If these types aren't equal then we've probably peeled off a layer of arrays.
self.same_type_modulo_infer(*root_ty, exp_found.expected)
} else {
true
};
if should_suggest_fixes {
self.suggest_tuple_pattern(cause, &exp_found, diag);
@ -1786,7 +1775,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
.filter_map(|variant| {
let sole_field = &variant.fields[0];
let sole_field_ty = sole_field.ty(self.tcx, substs);
if same_type_modulo_infer(sole_field_ty, exp_found.found) {
if self.same_type_modulo_infer(sole_field_ty, exp_found.found) {
let variant_path =
with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
// FIXME #56861: DRYer prelude filtering
@ -1902,12 +1891,15 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
self.get_impl_future_output_ty(exp_found.expected).map(Binder::skip_binder),
self.get_impl_future_output_ty(exp_found.found).map(Binder::skip_binder),
) {
(Some(exp), Some(found)) if same_type_modulo_infer(exp, found) => match cause.code() {
ObligationCauseCode::IfExpression(box IfExpressionCause { then, .. }) => {
(Some(exp), Some(found)) if self.same_type_modulo_infer(exp, found) => match cause
.code()
{
ObligationCauseCode::IfExpression(box IfExpressionCause { then_id, .. }) => {
let then_span = self.find_block_span_from_hir_id(*then_id);
diag.multipart_suggestion(
"consider `await`ing on both `Future`s",
vec![
(then.shrink_to_hi(), ".await".to_string()),
(then_span.shrink_to_hi(), ".await".to_string()),
(exp_span.shrink_to_hi(), ".await".to_string()),
],
Applicability::MaybeIncorrect,
@ -1934,7 +1926,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
diag.help("consider `await`ing on both `Future`s");
}
},
(_, Some(ty)) if same_type_modulo_infer(exp_found.expected, ty) => {
(_, Some(ty)) if self.same_type_modulo_infer(exp_found.expected, ty) => {
diag.span_suggestion_verbose(
exp_span.shrink_to_hi(),
"consider `await`ing on the `Future`",
@ -1942,11 +1934,20 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
Applicability::MaybeIncorrect,
);
}
(Some(ty), _) if same_type_modulo_infer(ty, exp_found.found) => match cause.code() {
ObligationCauseCode::Pattern { span: Some(span), .. }
| ObligationCauseCode::IfExpression(box IfExpressionCause { then: span, .. }) => {
(Some(ty), _) if self.same_type_modulo_infer(ty, exp_found.found) => match cause.code()
{
ObligationCauseCode::Pattern { span: Some(then_span), .. } => {
diag.span_suggestion_verbose(
span.shrink_to_hi(),
then_span.shrink_to_hi(),
"consider `await`ing on the `Future`",
".await",
Applicability::MaybeIncorrect,
);
}
ObligationCauseCode::IfExpression(box IfExpressionCause { then_id, .. }) => {
let then_span = self.find_block_span_from_hir_id(*then_id);
diag.span_suggestion_verbose(
then_span.shrink_to_hi(),
"consider `await`ing on the `Future`",
".await",
Applicability::MaybeIncorrect,
@ -1992,7 +1993,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
.iter()
.filter(|field| field.vis.is_accessible_from(field.did, self.tcx))
.map(|field| (field.name, field.ty(self.tcx, expected_substs)))
.find(|(_, ty)| same_type_modulo_infer(*ty, exp_found.found))
.find(|(_, ty)| self.same_type_modulo_infer(*ty, exp_found.found))
{
if let ObligationCauseCode::Pattern { span: Some(span), .. } = *cause.code() {
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
@ -2057,7 +2058,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
| (_, ty::Infer(_))
| (ty::Param(_), _)
| (ty::Infer(_), _) => {}
_ if same_type_modulo_infer(exp_ty, found_ty) => {}
_ if self.same_type_modulo_infer(exp_ty, found_ty) => {}
_ => show_suggestion = false,
};
}
@ -2179,7 +2180,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
) {
let [expected_tup_elem] = expected_fields[..] else { return };
if !same_type_modulo_infer(expected_tup_elem, found) {
if !self.same_type_modulo_infer(expected_tup_elem, found) {
return;
}
@ -2647,6 +2648,76 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
span.is_desugaring(DesugaringKind::QuestionMark)
&& self.tcx.is_diagnostic_item(sym::From, trait_def_id)
}
/// Structurally compares two types, modulo any inference variables.
///
/// Returns `true` if two types are equal, or if one type is an inference variable compatible
/// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
/// FloatVar inference type are compatible with themselves or their concrete types (Int and
/// Float types, respectively). When comparing two ADTs, these rules apply recursively.
pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
let (a, b) = self.resolve_vars_if_possible((a, b));
match (a.kind(), b.kind()) {
(&ty::Adt(def_a, substs_a), &ty::Adt(def_b, substs_b)) => {
if def_a != def_b {
return false;
}
substs_a
.types()
.zip(substs_b.types())
.all(|(a, b)| self.same_type_modulo_infer(a, b))
}
(&ty::FnDef(did_a, substs_a), &ty::FnDef(did_b, substs_b)) => {
if did_a != did_b {
return false;
}
substs_a
.types()
.zip(substs_b.types())
.all(|(a, b)| self.same_type_modulo_infer(a, b))
}
(&ty::Int(_) | &ty::Uint(_), &ty::Infer(ty::InferTy::IntVar(_)))
| (
&ty::Infer(ty::InferTy::IntVar(_)),
&ty::Int(_) | &ty::Uint(_) | &ty::Infer(ty::InferTy::IntVar(_)),
)
| (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
| (
&ty::Infer(ty::InferTy::FloatVar(_)),
&ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
)
| (&ty::Infer(ty::InferTy::TyVar(_)), _)
| (_, &ty::Infer(ty::InferTy::TyVar(_))) => true,
(&ty::Ref(_, ty_a, mut_a), &ty::Ref(_, ty_b, mut_b)) => {
mut_a == mut_b && self.same_type_modulo_infer(ty_a, ty_b)
}
(&ty::RawPtr(a), &ty::RawPtr(b)) => {
a.mutbl == b.mutbl && self.same_type_modulo_infer(a.ty, b.ty)
}
(&ty::Slice(a), &ty::Slice(b)) => self.same_type_modulo_infer(a, b),
(&ty::Array(a_ty, a_ct), &ty::Array(b_ty, b_ct)) => {
self.same_type_modulo_infer(a_ty, b_ty) && a_ct == b_ct
}
(&ty::Tuple(a), &ty::Tuple(b)) => {
if a.len() != b.len() {
return false;
}
std::iter::zip(a.iter(), b.iter()).all(|(a, b)| self.same_type_modulo_infer(a, b))
}
(&ty::FnPtr(a), &ty::FnPtr(b)) => {
let a = a.skip_binder().inputs_and_output;
let b = b.skip_binder().inputs_and_output;
if a.len() != b.len() {
return false;
}
std::iter::zip(a.iter(), b.iter()).all(|(a, b)| self.same_type_modulo_infer(a, b))
}
// FIXME(compiler-errors): This needs to be generalized more
_ => a == b,
}
}
}
impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
@ -2798,3 +2869,237 @@ impl TyCategory {
}
}
}
impl<'tcx> InferCtxt<'_, 'tcx> {
/// Given a [`hir::Block`], get the span of its last expression or
/// statement, peeling off any inner blocks.
pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
let block = block.innermost_block();
if let Some(expr) = &block.expr {
expr.span
} else if let Some(stmt) = block.stmts.last() {
// possibly incorrect trailing `;` in the else arm
stmt.span
} else {
// empty block; point at its entirety
block.span
}
}
/// Given a [`hir::HirId`] for a block, get the span of its last expression
/// or statement, peeling off any inner blocks.
pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
match self.tcx.hir().get(hir_id) {
hir::Node::Block(blk) => self.find_block_span(blk),
// The parser was in a weird state if either of these happen, but
// it's better not to panic.
hir::Node::Expr(e) => e.span,
_ => rustc_span::DUMMY_SP,
}
}
/// Be helpful when the user wrote `{... expr; }` and taking the `;` off
/// is enough to fix the error.
pub fn could_remove_semicolon(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
) -> Option<(Span, StatementAsExpression)> {
let blk = blk.innermost_block();
// Do not suggest if we have a tail expr.
if blk.expr.is_some() {
return None;
}
let last_stmt = blk.stmts.last()?;
let hir::StmtKind::Semi(ref last_expr) = last_stmt.kind else {
return None;
};
let last_expr_ty = self.in_progress_typeck_results?.borrow().expr_ty_opt(*last_expr)?;
let needs_box = match (last_expr_ty.kind(), expected_ty.kind()) {
_ if last_expr_ty.references_error() => return None,
_ if self.same_type_modulo_infer(last_expr_ty, expected_ty) => {
StatementAsExpression::CorrectType
}
(ty::Opaque(last_def_id, _), ty::Opaque(exp_def_id, _))
if last_def_id == exp_def_id =>
{
StatementAsExpression::CorrectType
}
(ty::Opaque(last_def_id, last_bounds), ty::Opaque(exp_def_id, exp_bounds)) => {
debug!(
"both opaque, likely future {:?} {:?} {:?} {:?}",
last_def_id, last_bounds, exp_def_id, exp_bounds
);
let last_local_id = last_def_id.as_local()?;
let exp_local_id = exp_def_id.as_local()?;
match (
&self.tcx.hir().expect_item(last_local_id).kind,
&self.tcx.hir().expect_item(exp_local_id).kind,
) {
(
hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: last_bounds, .. }),
hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: exp_bounds, .. }),
) if iter::zip(*last_bounds, *exp_bounds).all(|(left, right)| {
match (left, right) {
(
hir::GenericBound::Trait(tl, ml),
hir::GenericBound::Trait(tr, mr),
) if tl.trait_ref.trait_def_id() == tr.trait_ref.trait_def_id()
&& ml == mr =>
{
true
}
(
hir::GenericBound::LangItemTrait(langl, _, _, argsl),
hir::GenericBound::LangItemTrait(langr, _, _, argsr),
) if langl == langr => {
// FIXME: consider the bounds!
debug!("{:?} {:?}", argsl, argsr);
true
}
_ => false,
}
}) =>
{
StatementAsExpression::NeedsBoxing
}
_ => StatementAsExpression::CorrectType,
}
}
_ => return None,
};
let span = if last_stmt.span.from_expansion() {
let mac_call = rustc_span::source_map::original_sp(last_stmt.span, blk.span);
self.tcx.sess.source_map().mac_call_stmt_semi_span(mac_call)?
} else {
last_stmt.span.with_lo(last_stmt.span.hi() - BytePos(1))
};
Some((span, needs_box))
}
/// Suggest returning a local binding with a compatible type if the block
/// has no return expression.
pub fn consider_returning_binding(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
err: &mut Diagnostic,
) -> bool {
let blk = blk.innermost_block();
// Do not suggest if we have a tail expr.
if blk.expr.is_some() {
return false;
}
let mut shadowed = FxHashSet::default();
let mut candidate_idents = vec![];
let mut find_compatible_candidates = |pat: &hir::Pat<'_>| {
if let hir::PatKind::Binding(_, hir_id, ident, _) = &pat.kind
&& let Some(pat_ty) = self
.in_progress_typeck_results
.and_then(|typeck_results| typeck_results.borrow().node_type_opt(*hir_id))
{
let pat_ty = self.resolve_vars_if_possible(pat_ty);
if self.same_type_modulo_infer(pat_ty, expected_ty)
&& !(pat_ty, expected_ty).references_error()
&& shadowed.insert(ident.name)
{
candidate_idents.push((*ident, pat_ty));
}
}
true
};
let hir = self.tcx.hir();
for stmt in blk.stmts.iter().rev() {
let hir::StmtKind::Local(local) = &stmt.kind else { continue; };
local.pat.walk(&mut find_compatible_candidates);
}
match hir.find(hir.get_parent_node(blk.hir_id)) {
Some(hir::Node::Expr(hir::Expr { hir_id, .. })) => {
match hir.find(hir.get_parent_node(*hir_id)) {
Some(hir::Node::Arm(hir::Arm { pat, .. })) => {
pat.walk(&mut find_compatible_candidates);
}
Some(
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body), .. })
| hir::Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Fn(_, body),
..
})
| hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(body)),
..
})
| hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(hir::Closure { body, .. }),
..
}),
) => {
for param in hir.body(*body).params {
param.pat.walk(&mut find_compatible_candidates);
}
}
Some(hir::Node::Expr(hir::Expr {
kind:
hir::ExprKind::If(
hir::Expr { kind: hir::ExprKind::Let(let_), .. },
then_block,
_,
),
..
})) if then_block.hir_id == *hir_id => {
let_.pat.walk(&mut find_compatible_candidates);
}
_ => {}
}
}
_ => {}
}
match &candidate_idents[..] {
[(ident, _ty)] => {
let sm = self.tcx.sess.source_map();
if let Some(stmt) = blk.stmts.last() {
let stmt_span = sm.stmt_span(stmt.span, blk.span);
let sugg = if sm.is_multiline(blk.span)
&& let Some(spacing) = sm.indentation_before(stmt_span)
{
format!("\n{spacing}{ident}")
} else {
format!(" {ident}")
};
err.span_suggestion_verbose(
stmt_span.shrink_to_hi(),
format!("consider returning the local binding `{ident}`"),
sugg,
Applicability::MaybeIncorrect,
);
} else {
let sugg = if sm.is_multiline(blk.span)
&& let Some(spacing) = sm.indentation_before(blk.span.shrink_to_lo())
{
format!("\n{spacing} {ident}\n{spacing}")
} else {
format!(" {ident} ")
};
let left_span = sm.span_through_char(blk.span, '{').shrink_to_hi();
err.span_suggestion_verbose(
sm.span_extend_while(left_span, |c| c.is_whitespace()).unwrap_or(left_span),
format!("consider returning the local binding `{ident}`"),
sugg,
Applicability::MaybeIncorrect,
);
}
true
}
values if (1..3).contains(&values.len()) => {
let spans = values.iter().map(|(ident, _)| ident.span).collect::<Vec<_>>();
err.span_note(spans, "consider returning one of these bindings");
true
}
_ => false,
}
}
}

23
compiler/rustc_middle/src/traits/mod.rs
View file

@ -351,7 +351,7 @@ pub enum ObligationCauseCode<'tcx> {
ConstPatternStructural,
/// Computing common supertype in an if expression
IfExpression(Box<IfExpressionCause>),
IfExpression(Box<IfExpressionCause<'tcx>>),
/// Computing common supertype of an if expression with no else counter-part
IfExpressionWithNoElse,
@ -488,22 +488,27 @@ impl<'tcx> ty::Lift<'tcx> for StatementAsExpression {
#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
pub struct MatchExpressionArmCause<'tcx> {
pub arm_block_id: Option<hir::HirId>,
pub arm_ty: Ty<'tcx>,
pub arm_span: Span,
pub prior_arm_block_id: Option<hir::HirId>,
pub prior_arm_ty: Ty<'tcx>,
pub prior_arm_span: Span,
pub scrut_span: Span,
pub semi_span: Option<(Span, StatementAsExpression)>,
pub source: hir::MatchSource,
pub prior_arms: Vec<Span>,
pub last_ty: Ty<'tcx>,
pub scrut_hir_id: hir::HirId,
pub opt_suggest_box_span: Option<Span>,
}
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct IfExpressionCause {
pub then: Span,
pub else_sp: Span,
pub outer: Option<Span>,
pub semicolon: Option<(Span, StatementAsExpression)>,
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
#[derive(Lift, TypeFoldable, TypeVisitable)]
pub struct IfExpressionCause<'tcx> {
pub then_id: hir::HirId,
pub else_id: hir::HirId,
pub then_ty: Ty<'tcx>,
pub else_ty: Ty<'tcx>,
pub outer_span: Option<Span>,
pub opt_suggest_box_span: Option<Span>,
}

1
compiler/rustc_middle/src/traits/structural_impls.rs
View file

@ -130,7 +130,6 @@ impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceConstDestructData<N> {
// Lift implementations
TrivialTypeTraversalAndLiftImpls! {
super::IfExpressionCause,
super::ImplSourceDiscriminantKindData,
super::ImplSourcePointeeData,
}

3
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View file

@ -22,7 +22,6 @@ use rustc_hir::intravisit::Visitor;
use rustc_hir::GenericParam;
use rustc_hir::Item;
use rustc_hir::Node;
use rustc_infer::infer::error_reporting::same_type_modulo_infer;
use rustc_infer::traits::TraitEngine;
use rustc_middle::traits::select::OverflowError;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
@ -640,7 +639,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
if expected.len() == 1 { "" } else { "s" },
)
);
} else if !same_type_modulo_infer(given_ty, expected_ty) {
} else if !self.same_type_modulo_infer(given_ty, expected_ty) {
// Print type mismatch
let (expected_args, given_args) =
self.cmp(given_ty, expected_ty);

169
compiler/rustc_typeck/src/check/_match.rs
View file

@ -9,7 +9,6 @@ use rustc_span::Span;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use rustc_trait_selection::traits::{
IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
StatementAsExpression,
};
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@ -75,8 +74,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
};
let mut other_arms = vec![]; // Used only for diagnostics.
let mut prior_arm_ty = None;
for (i, arm) in arms.iter().enumerate() {
let mut prior_arm = None;
for arm in arms {
if let Some(g) = &arm.guard {
self.diverges.set(Diverges::Maybe);
match g {
@ -96,21 +95,28 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let opt_suggest_box_span = self.opt_suggest_box_span(arm_ty, orig_expected);
let (arm_span, semi_span) =
self.get_appropriate_arm_semicolon_removal_span(&arms, i, prior_arm_ty, arm_ty);
let (span, code) = match i {
let (arm_block_id, arm_span) = if let hir::ExprKind::Block(blk, _) = arm.body.kind {
(Some(blk.hir_id), self.find_block_span(blk))
} else {
(None, arm.body.span)
};
let (span, code) = match prior_arm {
// The reason for the first arm to fail is not that the match arms diverge,
// but rather that there's a prior obligation that doesn't hold.
0 => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)),
_ => (
None => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)),
Some((prior_arm_block_id, prior_arm_ty, prior_arm_span)) => (
expr.span,
ObligationCauseCode::MatchExpressionArm(Box::new(MatchExpressionArmCause {
arm_block_id,
arm_span,
arm_ty,
prior_arm_block_id,
prior_arm_ty,
prior_arm_span,
scrut_span: scrut.span,
semi_span,
source: match_src,
prior_arms: other_arms.clone(),
last_ty: prior_arm_ty.unwrap(),
scrut_hir_id: scrut.hir_id,
opt_suggest_box_span,
})),
@ -139,7 +145,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let ret_ty = ret_coercion.borrow().expected_ty();
let ret_ty = self.inh.infcx.shallow_resolve(ret_ty);
self.can_coerce(arm_ty, ret_ty)
&& prior_arm_ty.map_or(true, |t| self.can_coerce(t, ret_ty))
&& prior_arm.map_or(true, |(_, t, _)| self.can_coerce(t, ret_ty))
// The match arms need to unify for the case of `impl Trait`.
&& !matches!(ret_ty.kind(), ty::Opaque(..))
}
@ -181,7 +187,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
if other_arms.len() > 5 {
other_arms.remove(0);
}
prior_arm_ty = Some(arm_ty);
prior_arm = Some((arm_block_id, arm_ty, arm_span));
}
// If all of the arms in the `match` diverge,
@ -207,28 +214,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
match_ty
}
fn get_appropriate_arm_semicolon_removal_span(
&self,
arms: &'tcx [hir::Arm<'tcx>],
i: usize,
prior_arm_ty: Option<Ty<'tcx>>,
arm_ty: Ty<'tcx>,
) -> (Span, Option<(Span, StatementAsExpression)>) {
let arm = &arms[i];
let (arm_span, mut semi_span) = if let hir::ExprKind::Block(blk, _) = &arm.body.kind {
self.find_block_span(blk, prior_arm_ty)
} else {
(arm.body.span, None)
};
if semi_span.is_none() && i > 0 {
if let hir::ExprKind::Block(blk, _) = &arms[i - 1].body.kind {
let (_, semi_span_prev) = self.find_block_span(blk, Some(arm_ty));
semi_span = semi_span_prev;
}
}
(arm_span, semi_span)
}
/// When the previously checked expression (the scrutinee) diverges,
/// warn the user about the match arms being unreachable.
fn warn_arms_when_scrutinee_diverges(&self, arms: &'tcx [hir::Arm<'tcx>]) {
@ -313,7 +298,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
else_ty: Ty<'tcx>,
opt_suggest_box_span: Option<Span>,
) -> ObligationCause<'tcx> {
let mut outer_sp = if self.tcx.sess.source_map().is_multiline(span) {
let mut outer_span = if self.tcx.sess.source_map().is_multiline(span) {
// The `if`/`else` isn't in one line in the output, include some context to make it
// clear it is an if/else expression:
// ```
@ -339,69 +324,67 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
None
};
let mut remove_semicolon = None;
let error_sp = if let ExprKind::Block(block, _) = &else_expr.kind {
let (error_sp, semi_sp) = self.find_block_span(block, Some(then_ty));
remove_semicolon = semi_sp;
if block.expr.is_none() && block.stmts.is_empty() {
// Avoid overlapping spans that aren't as readable:
// ```
// 2 | let x = if true {
// | _____________-
// 3 | | 3
// | | - expected because of this
// 4 | | } else {
// | |____________^
// 5 | ||
// 6 | || };
// | || ^
// | ||_____|
// | |______if and else have incompatible types
// | expected integer, found `()`
// ```
// by not pointing at the entire expression:
// ```
// 2 | let x = if true {
// | ------- `if` and `else` have incompatible types
// 3 | 3
// | - expected because of this
// 4 | } else {
// | ____________^
// 5 | |
// 6 | | };
// | |_____^ expected integer, found `()`
// ```
if outer_sp.is_some() {
outer_sp = Some(self.tcx.sess.source_map().guess_head_span(span));
}
let (error_sp, else_id) = if let ExprKind::Block(block, _) = &else_expr.kind {
let block = block.innermost_block();
// Avoid overlapping spans that aren't as readable:
// ```
// 2 | let x = if true {
// | _____________-
// 3 | | 3
// | | - expected because of this
// 4 | | } else {
// | |____________^
// 5 | ||
// 6 | || };
// | || ^
// | ||_____|
// | |______if and else have incompatible types
// | expected integer, found `()`
// ```
// by not pointing at the entire expression:
// ```
// 2 | let x = if true {
// | ------- `if` and `else` have incompatible types
// 3 | 3
// | - expected because of this
// 4 | } else {
// | ____________^
// 5 | |
// 6 | | };
// | |_____^ expected integer, found `()`
// ```
if block.expr.is_none() && block.stmts.is_empty()
&& let Some(outer_span) = &mut outer_span
{
*outer_span = self.tcx.sess.source_map().guess_head_span(*outer_span);
}
error_sp
(self.find_block_span(block), block.hir_id)
} else {
// shouldn't happen unless the parser has done something weird
else_expr.span
(else_expr.span, else_expr.hir_id)
};
// Compute `Span` of `then` part of `if`-expression.
let then_sp = if let ExprKind::Block(block, _) = &then_expr.kind {
let (then_sp, semi_sp) = self.find_block_span(block, Some(else_ty));
remove_semicolon = remove_semicolon.or(semi_sp);
let then_id = if let ExprKind::Block(block, _) = &then_expr.kind {
let block = block.innermost_block();
// Exclude overlapping spans
if block.expr.is_none() && block.stmts.is_empty() {
outer_sp = None; // same as in `error_sp`; cleanup output
outer_span = None;
}
then_sp
block.hir_id
} else {
// shouldn't happen unless the parser has done something weird
then_expr.span
then_expr.hir_id
};
// Finally construct the cause:
self.cause(
error_sp,
ObligationCauseCode::IfExpression(Box::new(IfExpressionCause {
then: then_sp,
else_sp: error_sp,
outer: outer_sp,
semicolon: remove_semicolon,
else_id,
then_id,
then_ty,
else_ty,
outer_span,
opt_suggest_box_span,
})),
)
@ -482,22 +465,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}
fn find_block_span(
&self,
block: &'tcx hir::Block<'tcx>,
expected_ty: Option<Ty<'tcx>>,
) -> (Span, Option<(Span, StatementAsExpression)>) {
if let Some(expr) = &block.expr {
(expr.span, None)
} else if let Some(stmt) = block.stmts.last() {
// possibly incorrect trailing `;` in the else arm
(stmt.span, expected_ty.and_then(|ty| self.could_remove_semicolon(block, ty)))
} else {
// empty block; point at its entirety
(block.span, None)
}
}
// When we have a `match` as a tail expression in a `fn` with a returned `impl Trait`
// we check if the different arms would work with boxed trait objects instead and
// provide a structured suggestion in that case.

84
compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
View file

@ -30,17 +30,15 @@ use rustc_middle::ty::{
};
use rustc_session::lint;
use rustc_span::hygiene::DesugaringKind;
use rustc_span::source_map::{original_sp, DUMMY_SP};
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::{self, BytePos, Span};
use rustc_span::{Span, DUMMY_SP};
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_trait_selection::traits::{
self, ObligationCause, ObligationCauseCode, StatementAsExpression, TraitEngine, TraitEngineExt,
self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt,
};
use std::collections::hash_map::Entry;
use std::iter;
use std::slice;
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@ -1059,84 +1057,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
));
}
pub(in super::super) fn could_remove_semicolon(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
) -> Option<(Span, StatementAsExpression)> {
// Be helpful when the user wrote `{... expr;}` and
// taking the `;` off is enough to fix the error.
let last_stmt = blk.stmts.last()?;
let hir::StmtKind::Semi(ref last_expr) = last_stmt.kind else {
return None;
};
let last_expr_ty = self.node_ty(last_expr.hir_id);
let needs_box = match (last_expr_ty.kind(), expected_ty.kind()) {
(ty::Opaque(last_def_id, _), ty::Opaque(exp_def_id, _))
if last_def_id == exp_def_id =>
{
StatementAsExpression::CorrectType
}
(ty::Opaque(last_def_id, last_bounds), ty::Opaque(exp_def_id, exp_bounds)) => {
debug!(
"both opaque, likely future {:?} {:?} {:?} {:?}",
last_def_id, last_bounds, exp_def_id, exp_bounds
);
let last_local_id = last_def_id.as_local()?;
let exp_local_id = exp_def_id.as_local()?;
match (
&self.tcx.hir().expect_item(last_local_id).kind,
&self.tcx.hir().expect_item(exp_local_id).kind,
) {
(
hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: last_bounds, .. }),
hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds: exp_bounds, .. }),
) if iter::zip(*last_bounds, *exp_bounds).all(|(left, right)| {
match (left, right) {
(
hir::GenericBound::Trait(tl, ml),
hir::GenericBound::Trait(tr, mr),
) if tl.trait_ref.trait_def_id() == tr.trait_ref.trait_def_id()
&& ml == mr =>
{
true
}
(
hir::GenericBound::LangItemTrait(langl, _, _, argsl),
hir::GenericBound::LangItemTrait(langr, _, _, argsr),
) if langl == langr => {
// FIXME: consider the bounds!
debug!("{:?} {:?}", argsl, argsr);
true
}
_ => false,
}
}) =>
{
StatementAsExpression::NeedsBoxing
}
_ => StatementAsExpression::CorrectType,
}
}
_ => StatementAsExpression::CorrectType,
};
if (matches!(last_expr_ty.kind(), ty::Error(_))
|| self.can_sub(self.param_env, last_expr_ty, expected_ty).is_err())
&& matches!(needs_box, StatementAsExpression::CorrectType)
{
return None;
}
let span = if last_stmt.span.from_expansion() {
let mac_call = original_sp(last_stmt.span, blk.span);
self.tcx.sess.source_map().mac_call_stmt_semi_span(mac_call)?
} else {
last_stmt.span.with_lo(last_stmt.span.hi() - BytePos(1))
};
Some((span, needs_box))
}
// Instantiates the given path, which must refer to an item with the given
// number of type parameters and type.
#[instrument(skip(self, span), level = "debug")]

116
compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
View file

@ -3,7 +3,6 @@ use crate::astconv::AstConv;
use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel};
use rustc_ast::util::parser::ExprPrecedence;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{Applicability, Diagnostic, MultiSpan};
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind};
@ -14,7 +13,7 @@ use rustc_hir::{
use rustc_infer::infer::{self, TyCtxtInferExt};
use rustc_infer::traits::{self, StatementAsExpression};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::{self, Binder, IsSuggestable, Subst, ToPredicate, Ty, TypeVisitable};
use rustc_middle::ty::{self, Binder, IsSuggestable, Subst, ToPredicate, Ty};
use rustc_span::symbol::sym;
use rustc_span::Span;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
@ -904,117 +903,4 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
false
}
}
pub(crate) fn consider_returning_binding(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
err: &mut Diagnostic,
) {
let mut shadowed = FxHashSet::default();
let mut candidate_idents = vec![];
let mut find_compatible_candidates = |pat: &hir::Pat<'_>| {
if let hir::PatKind::Binding(_, hir_id, ident, _) = &pat.kind
&& let Some(pat_ty) = self.typeck_results.borrow().node_type_opt(*hir_id)
{
let pat_ty = self.resolve_vars_if_possible(pat_ty);
if self.can_coerce(pat_ty, expected_ty)
&& !(pat_ty, expected_ty).references_error()
&& shadowed.insert(ident.name)
{
candidate_idents.push((*ident, pat_ty));
}
}
true
};
let hir = self.tcx.hir();
for stmt in blk.stmts.iter().rev() {
let StmtKind::Local(local) = &stmt.kind else { continue; };
local.pat.walk(&mut find_compatible_candidates);
}
match hir.find(hir.get_parent_node(blk.hir_id)) {
Some(hir::Node::Expr(hir::Expr { hir_id, .. })) => {
match hir.find(hir.get_parent_node(*hir_id)) {
Some(hir::Node::Arm(hir::Arm { pat, .. })) => {
pat.walk(&mut find_compatible_candidates);
}
Some(
hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body), .. })
| hir::Node::ImplItem(hir::ImplItem {
kind: hir::ImplItemKind::Fn(_, body),
..
})
| hir::Node::TraitItem(hir::TraitItem {
kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(body)),
..
})
| hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(hir::Closure { body, .. }),
..
}),
) => {
for param in hir.body(*body).params {
param.pat.walk(&mut find_compatible_candidates);
}
}
Some(hir::Node::Expr(hir::Expr {
kind:
hir::ExprKind::If(
hir::Expr { kind: hir::ExprKind::Let(let_), .. },
then_block,
_,
),
..
})) if then_block.hir_id == *hir_id => {
let_.pat.walk(&mut find_compatible_candidates);
}
_ => {}
}
}
_ => {}
}
match &candidate_idents[..] {
[(ident, _ty)] => {
let sm = self.tcx.sess.source_map();
if let Some(stmt) = blk.stmts.last() {
let stmt_span = sm.stmt_span(stmt.span, blk.span);
let sugg = if sm.is_multiline(blk.span)
&& let Some(spacing) = sm.indentation_before(stmt_span)
{
format!("\n{spacing}{ident}")
} else {
format!(" {ident}")
};
err.span_suggestion_verbose(
stmt_span.shrink_to_hi(),
format!("consider returning the local binding `{ident}`"),
sugg,
Applicability::MachineApplicable,
);
} else {
let sugg = if sm.is_multiline(blk.span)
&& let Some(spacing) = sm.indentation_before(blk.span.shrink_to_lo())
{
format!("\n{spacing} {ident}\n{spacing}")
} else {
format!(" {ident} ")
};
let left_span = sm.span_through_char(blk.span, '{').shrink_to_hi();
err.span_suggestion_verbose(
sm.span_extend_while(left_span, |c| c.is_whitespace()).unwrap_or(left_span),
format!("consider returning the local binding `{ident}`"),
sugg,
Applicability::MachineApplicable,
);
}
}
values if (1..3).contains(&values.len()) => {
let spans = values.iter().map(|(ident, _)| ident.span).collect::<Vec<_>>();
err.span_note(spans, "consider returning one of these bindings");
}
_ => {}
}
}
}

18
src/test/ui/async-await/async-block-control-flow-static-semantics.stderr
View file

@ -18,14 +18,6 @@ LL | | break 0u8;
LL | | };
| |_________- enclosing `async` block
error[E0271]: type mismatch resolving `<impl Future<Output = u8> as Future>::Output == ()`
--> $DIR/async-block-control-flow-static-semantics.rs:26:39
|
LL | let _: &dyn Future<Output = ()> = &block;
| ^^^^^^ expected `()`, found `u8`
|
= note: required for the cast from `impl Future<Output = u8>` to the object type `dyn Future<Output = ()>`
error[E0308]: mismatched types
--> $DIR/async-block-control-flow-static-semantics.rs:21:58
|
@ -40,7 +32,7 @@ LL | | }
| |_^ expected `u8`, found `()`
error[E0271]: type mismatch resolving `<impl Future<Output = u8> as Future>::Output == ()`
--> $DIR/async-block-control-flow-static-semantics.rs:17:39
--> $DIR/async-block-control-flow-static-semantics.rs:26:39
|
LL | let _: &dyn Future<Output = ()> = &block;
| ^^^^^^ expected `()`, found `u8`
@ -55,6 +47,14 @@ LL | fn return_targets_async_block_not_fn() -> u8 {
| |
| implicitly returns `()` as its body has no tail or `return` expression
error[E0271]: type mismatch resolving `<impl Future<Output = u8> as Future>::Output == ()`
--> $DIR/async-block-control-flow-static-semantics.rs:17:39
|
LL | let _: &dyn Future<Output = ()> = &block;
| ^^^^^^ expected `()`, found `u8`
|
= note: required for the cast from `impl Future<Output = u8>` to the object type `dyn Future<Output = ()>`
error[E0308]: mismatched types
--> $DIR/async-block-control-flow-static-semantics.rs:47:44
|

2
src/test/ui/issues/issue-59494.stderr
View file

@ -7,8 +7,6 @@ LL | let t8 = t8n(t7, t7p(f, g));
| required by a bound introduced by this call
|
= help: the trait `Fn<(_,)>` is not implemented for `impl Fn(((_, _), _))`
= note: expected a closure with arguments `(((_, _), _),)`
found a closure with arguments `(_,)`
note: required by a bound in `t8n`
--> $DIR/issue-59494.rs:5:45
|

23
src/test/ui/suggestions/return-bindings.fixed
View file

@ -1,23 +0,0 @@
// run-rustfix
#![allow(unused)]
fn a(i: i32) -> i32 { i }
//~^ ERROR mismatched types
fn b(opt_str: Option<String>) {
let s: String = if let Some(s) = opt_str {
s
//~^ ERROR mismatched types
} else {
String::new()
};
}
fn c() -> Option<i32> {
//~^ ERROR mismatched types
let x = Some(1);
x
}
fn main() {}

34
src/test/ui/suggestions/return-bindings.rs
View file

@ -1,5 +1,3 @@
// run-rustfix
#![allow(unused)]
fn a(i: i32) -> i32 {}
@ -18,4 +16,36 @@ fn c() -> Option<i32> {
let x = Some(1);
}
fn d(opt_str: Option<String>) {
let s: String = if let Some(s) = opt_str {
//~^ ERROR mismatched types
} else {
String::new()
};
}
fn d2(opt_str: Option<String>) {
let s = if let Some(s) = opt_str {
} else {
String::new()
//~^ ERROR `if` and `else` have incompatible types
};
}
fn e(opt_str: Option<String>) {
let s: String = match opt_str {
Some(s) => {}
//~^ ERROR mismatched types
None => String::new(),
};
}
fn e2(opt_str: Option<String>) {
let s = match opt_str {
Some(s) => {}
None => String::new(),
//~^ ERROR `match` arms have incompatible types
};
}
fn main() {}

70
src/test/ui/suggestions/return-bindings.stderr
View file

@ -1,5 +1,5 @@
error[E0308]: mismatched types
--> $DIR/return-bindings.rs:5:17
--> $DIR/return-bindings.rs:3:17
|
LL | fn a(i: i32) -> i32 {}
| - ^^^ expected `i32`, found `()`
@ -12,7 +12,7 @@ LL | fn a(i: i32) -> i32 { i }
| +
error[E0308]: mismatched types
--> $DIR/return-bindings.rs:9:46
--> $DIR/return-bindings.rs:7:46
|
LL | let s: String = if let Some(s) = opt_str {
| ______________________________________________^
@ -28,7 +28,7 @@ LL ~
|
error[E0308]: mismatched types
--> $DIR/return-bindings.rs:16:11
--> $DIR/return-bindings.rs:14:11
|
LL | fn c() -> Option<i32> {
| - ^^^^^^^^^^^ expected enum `Option`, found `()`
@ -43,6 +43,68 @@ LL ~ let x = Some(1);
LL + x
|
error: aborting due to 3 previous errors
error[E0308]: mismatched types
--> $DIR/return-bindings.rs:20:46
|
LL | let s: String = if let Some(s) = opt_str {
| ______________________________________________^
LL | |
LL | | } else {
| |_____^ expected struct `String`, found `()`
|
help: consider returning the local binding `s`
|
LL ~ let s: String = if let Some(s) = opt_str {
LL + s
LL ~
|
error[E0308]: `if` and `else` have incompatible types
--> $DIR/return-bindings.rs:30:9
|
LL | let s = if let Some(s) = opt_str {
| ______________________________________-
LL | | } else {
| |_____- expected because of this
LL | String::new()
| ^^^^^^^^^^^^^ expected `()`, found struct `String`
|
help: consider returning the local binding `s`
|
LL ~ let s = if let Some(s) = opt_str {
LL + s
LL ~ } else {
|
error[E0308]: mismatched types
--> $DIR/return-bindings.rs:37:20
|
LL | Some(s) => {}
| ^^ expected struct `String`, found `()`
|
help: consider returning the local binding `s`
|
LL | Some(s) => { s }
| +
error[E0308]: `match` arms have incompatible types
--> $DIR/return-bindings.rs:46:17
|
LL | let s = match opt_str {
| _____________-
LL | | Some(s) => {}
| | -- this is found to be of type `()`
LL | | None => String::new(),
| | ^^^^^^^^^^^^^ expected `()`, found struct `String`
LL | |
LL | | };
| |_____- `match` arms have incompatible types
|
help: consider returning the local binding `s`
|
LL | Some(s) => { s }
| +
error: aborting due to 7 previous errors
For more information about this error, try `rustc --explain E0308`.