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Do if-expression obligation stuff less eagerly

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This commit is contained in:
Michael Goulet 2022-07-21 00:03:02 +00:00
parent 3d9dd681f5
commit 99c32570bb
11 changed files with 411 additions and 350 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 peel_blocks(&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)]

335
compiler/rustc_infer/src/infer/error_reporting/mod.rs
View file

@ -721,25 +721,39 @@ 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");
}
let semicolon = if let hir::Node::Block(blk) = self.tcx.hir().get(then_id)
&& let Some(remove_semicolon) = self.could_remove_semicolon(blk, else_ty)
{
Some(remove_semicolon)
} else if let hir::Node::Block(blk) = self.tcx.hir().get(else_id)
&& let Some(remove_semicolon) = self.could_remove_semicolon(blk, then_ty)
{
Some(remove_semicolon)
} else {
None
};
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()),
(then_span.shrink_to_lo(), "Box::new(".to_string()),
(then_span.shrink_to_hi(), ")".to_string()),
(else_span.shrink_to_lo(), "Box::new(".to_string()),
(else_span.shrink_to_hi(), ")".to_string()),
(sp, String::new()),
],
Applicability::MachineApplicable,
@ -752,12 +766,21 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
Applicability::MachineApplicable,
);
}
} else {
let suggested = if let hir::Node::Block(blk) = self.tcx.hir().get(then_id) {
self.consider_returning_binding(blk, else_ty, err)
} else {
false
};
if !suggested && let hir::Node::Block(blk) = self.tcx.hir().get(else_id) {
self.consider_returning_binding(blk, then_ty, err);
}
}
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(),
);
}
}
@ -1870,40 +1893,41 @@ 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 self.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_span.shrink_to_hi(), ".await".to_string()),
(exp_span.shrink_to_hi(), ".await".to_string()),
],
Applicability::MaybeIncorrect,
);
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
prior_arms,
..
}) => {
if let [.., arm_span] = &prior_arms[..] {
diag.multipart_suggestion(
"consider `await`ing on both `Future`s",
vec![
(then.shrink_to_hi(), ".await".to_string()),
(arm_span.shrink_to_hi(), ".await".to_string()),
(exp_span.shrink_to_hi(), ".await".to_string()),
],
Applicability::MaybeIncorrect,
);
}
ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
prior_arms,
..
}) => {
if let [.., arm_span] = &prior_arms[..] {
diag.multipart_suggestion(
"consider `await`ing on both `Future`s",
vec![
(arm_span.shrink_to_hi(), ".await".to_string()),
(exp_span.shrink_to_hi(), ".await".to_string()),
],
Applicability::MaybeIncorrect,
);
} else {
diag.help("consider `await`ing on both `Future`s");
}
}
_ => {
} else {
diag.help("consider `await`ing on both `Future`s");
}
}
}
_ => {
diag.help("consider `await`ing on both `Future`s");
}
},
(_, Some(ty)) if self.same_type_modulo_infer(exp_found.expected, ty) => {
diag.span_suggestion_verbose(
exp_span.shrink_to_hi(),
@ -1914,10 +1938,18 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
(Some(ty), _) if self.same_type_modulo_infer(ty, exp_found.found) => match cause.code()
{
ObligationCauseCode::Pattern { span: Some(span), .. }
| ObligationCauseCode::IfExpression(box IfExpressionCause { then: span, .. }) => {
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,
@ -2808,3 +2840,230 @@ impl TyCategory {
}
}
}
impl<'tcx> InferCtxt<'_, 'tcx> {
pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
let block = block.peel_blocks();
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
}
}
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...
hir::Node::Expr(e) => e.span,
_ => rustc_span::DUMMY_SP,
}
}
pub fn could_remove_semicolon(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
) -> Option<(Span, StatementAsExpression)> {
let blk = blk.peel_blocks();
// Do not suggest if we have a tail expr.
if blk.expr.is_some() {
return None;
}
// 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.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))
}
pub fn consider_returning_binding(
&self,
blk: &'tcx hir::Block<'tcx>,
expected_ty: Ty<'tcx>,
err: &mut Diagnostic,
) -> bool {
let blk = blk.peel_blocks();
// 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,
}
}
}

16
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,
@ -498,12 +498,14 @@ pub struct MatchExpressionArmCause<'tcx> {
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,
}

124
compiler/rustc_typeck/src/check/_match.rs
View file

@ -216,13 +216,17 @@ impl<'a, 'tcx> FnCtxt<'a, '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)
(
self.find_block_span(blk),
prior_arm_ty
.and_then(|prior_arm_ty| self.could_remove_semicolon(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));
let semi_span_prev = self.could_remove_semicolon(blk, arm_ty);
semi_span = semi_span_prev;
}
}
@ -313,7 +317,7 @@ 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 +343,67 @@ 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.peel_blocks();
// 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.peel_blocks();
// 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 +484,6 @@ 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
|

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() {}

10
src/test/ui/suggestions/return-bindings.rs
View file

@ -1,5 +1,3 @@
// run-rustfix
#![allow(unused)]
fn a(i: i32) -> i32 {}
@ -18,4 +16,12 @@ 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 main() {}

24
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 +43,22 @@ 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: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0308`.