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Auto merge of rust-lang#12341 - y21:issue12337, r=dswij
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Check for try blocks in `question_mark` more consistently

Fixes rust-lang#12337

I split this PR up into two commits since this moves a method out of an `impl`, which makes for a pretty bad diff (the `&self` parameter is now unused, and there isn't a reason for that function to be part of the `impl` now).

The first commit is the actual relevant change and the 2nd commit just moves stuff (github's "hide whitespace" makes the diff easier to look at)

------------
Now for the actual issue:

`?` within `try {}` blocks desugars to a `break` to the block, rather than a `return`, so that changes behavior in those cases.

The lint has multiple patterns to look for and in *some* of them it already does correctly check whether we're in a try block, but this isn't done for all of its patterns.

We could add another `self.inside_try_block()` check to the function that looks for `let-else-return`, but I chose to actually just move those checks out and instead have them in `LintPass::check_{stmt,expr}`. This has the advantage that we can't (easily) accidentally forget to add that check in new patterns that might be added in the future.

(There's also a bit of a subtle interaction between two lints, where `question_mark`'s LintPass calls into `manual_let_else`, so I added a check to make sure we don't avoid linting for something that doesn't have anything to do with `?`)

changelog: [`question_mark`]: avoid linting on try blocks in more cases
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@bors
bors committed Mar 4, 2024
2 parents f75d8c7 + 1430623 commit e970fa5
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205 changes: 103 additions & 102 deletions clippy_lints/src/question_mark.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -203,108 +203,106 @@ fn expr_return_none_or_err(
}
}

impl QuestionMark {
fn inside_try_block(&self) -> bool {
self.try_block_depth_stack.last() > Some(&0)
}

/// Checks if the given expression on the given context matches the following structure:
///
/// ```ignore
/// if option.is_none() {
/// return None;
/// }
/// ```
///
/// ```ignore
/// if result.is_err() {
/// return result;
/// }
/// ```
///
/// If it matches, it will suggest to use the question mark operator instead
fn check_is_none_or_err_and_early_return<'tcx>(&self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if !self.inside_try_block()
&& let Some(higher::If { cond, then, r#else }) = higher::If::hir(expr)
&& !is_else_clause(cx.tcx, expr)
&& let ExprKind::MethodCall(segment, caller, ..) = &cond.kind
&& let caller_ty = cx.typeck_results().expr_ty(caller)
&& let if_block = IfBlockType::IfIs(caller, caller_ty, segment.ident.name, then)
&& (is_early_return(sym::Option, cx, &if_block) || is_early_return(sym::Result, cx, &if_block))
{
let mut applicability = Applicability::MachineApplicable;
let receiver_str = snippet_with_applicability(cx, caller.span, "..", &mut applicability);
let by_ref = !caller_ty.is_copy_modulo_regions(cx.tcx, cx.param_env)
&& !matches!(caller.kind, ExprKind::Call(..) | ExprKind::MethodCall(..));
let sugg = if let Some(else_inner) = r#else {
if eq_expr_value(cx, caller, peel_blocks(else_inner)) {
format!("Some({receiver_str}?)")
} else {
return;
}
/// Checks if the given expression on the given context matches the following structure:
///
/// ```ignore
/// if option.is_none() {
/// return None;
/// }
/// ```
///
/// ```ignore
/// if result.is_err() {
/// return result;
/// }
/// ```
///
/// If it matches, it will suggest to use the question mark operator instead
fn check_is_none_or_err_and_early_return<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if let Some(higher::If { cond, then, r#else }) = higher::If::hir(expr)
&& !is_else_clause(cx.tcx, expr)
&& let ExprKind::MethodCall(segment, caller, ..) = &cond.kind
&& let caller_ty = cx.typeck_results().expr_ty(caller)
&& let if_block = IfBlockType::IfIs(caller, caller_ty, segment.ident.name, then)
&& (is_early_return(sym::Option, cx, &if_block) || is_early_return(sym::Result, cx, &if_block))
{
let mut applicability = Applicability::MachineApplicable;
let receiver_str = snippet_with_applicability(cx, caller.span, "..", &mut applicability);
let by_ref = !caller_ty.is_copy_modulo_regions(cx.tcx, cx.param_env)
&& !matches!(caller.kind, ExprKind::Call(..) | ExprKind::MethodCall(..));
let sugg = if let Some(else_inner) = r#else {
if eq_expr_value(cx, caller, peel_blocks(else_inner)) {
format!("Some({receiver_str}?)")
} else {
format!("{receiver_str}{}?;", if by_ref { ".as_ref()" } else { "" })
};
return;
}
} else {
format!("{receiver_str}{}?;", if by_ref { ".as_ref()" } else { "" })
};

span_lint_and_sugg(
cx,
QUESTION_MARK,
expr.span,
"this block may be rewritten with the `?` operator",
"replace it with",
sugg,
applicability,
);
}
span_lint_and_sugg(
cx,
QUESTION_MARK,
expr.span,
"this block may be rewritten with the `?` operator",
"replace it with",
sugg,
applicability,
);
}
}

fn check_if_let_some_or_err_and_early_return<'tcx>(&self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if !self.inside_try_block()
&& let Some(higher::IfLet {
let_pat,
let_expr,
if_then,
if_else,
..
}) = higher::IfLet::hir(cx, expr)
&& !is_else_clause(cx.tcx, expr)
&& let PatKind::TupleStruct(ref path1, [field], ddpos) = let_pat.kind
&& ddpos.as_opt_usize().is_none()
&& let PatKind::Binding(BindingAnnotation(by_ref, _), bind_id, ident, None) = field.kind
&& let caller_ty = cx.typeck_results().expr_ty(let_expr)
&& let if_block = IfBlockType::IfLet(
cx.qpath_res(path1, let_pat.hir_id),
caller_ty,
ident.name,
let_expr,
if_then,
if_else,
)
&& ((is_early_return(sym::Option, cx, &if_block) && path_to_local_id(peel_blocks(if_then), bind_id))
|| is_early_return(sym::Result, cx, &if_block))
&& if_else
.map(|e| eq_expr_value(cx, let_expr, peel_blocks(e)))
.filter(|e| *e)
.is_none()
{
let mut applicability = Applicability::MachineApplicable;
let receiver_str = snippet_with_applicability(cx, let_expr.span, "..", &mut applicability);
let requires_semi = matches!(cx.tcx.parent_hir_node(expr.hir_id), Node::Stmt(_));
let sugg = format!(
"{receiver_str}{}?{}",
if by_ref == ByRef::Yes { ".as_ref()" } else { "" },
if requires_semi { ";" } else { "" }
);
span_lint_and_sugg(
cx,
QUESTION_MARK,
expr.span,
"this block may be rewritten with the `?` operator",
"replace it with",
sugg,
applicability,
);
}
fn check_if_let_some_or_err_and_early_return<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if let Some(higher::IfLet {
let_pat,
let_expr,
if_then,
if_else,
..
}) = higher::IfLet::hir(cx, expr)
&& !is_else_clause(cx.tcx, expr)
&& let PatKind::TupleStruct(ref path1, [field], ddpos) = let_pat.kind
&& ddpos.as_opt_usize().is_none()
&& let PatKind::Binding(BindingAnnotation(by_ref, _), bind_id, ident, None) = field.kind
&& let caller_ty = cx.typeck_results().expr_ty(let_expr)
&& let if_block = IfBlockType::IfLet(
cx.qpath_res(path1, let_pat.hir_id),
caller_ty,
ident.name,
let_expr,
if_then,
if_else,
)
&& ((is_early_return(sym::Option, cx, &if_block) && path_to_local_id(peel_blocks(if_then), bind_id))
|| is_early_return(sym::Result, cx, &if_block))
&& if_else
.map(|e| eq_expr_value(cx, let_expr, peel_blocks(e)))
.filter(|e| *e)
.is_none()
{
let mut applicability = Applicability::MachineApplicable;
let receiver_str = snippet_with_applicability(cx, let_expr.span, "..", &mut applicability);
let requires_semi = matches!(cx.tcx.parent_hir_node(expr.hir_id), Node::Stmt(_));
let sugg = format!(
"{receiver_str}{}?{}",
if by_ref == ByRef::Yes { ".as_ref()" } else { "" },
if requires_semi { ";" } else { "" }
);
span_lint_and_sugg(
cx,
QUESTION_MARK,
expr.span,
"this block may be rewritten with the `?` operator",
"replace it with",
sugg,
applicability,
);
}
}

impl QuestionMark {
fn inside_try_block(&self) -> bool {
self.try_block_depth_stack.last() > Some(&0)
}
}

Expand All @@ -324,15 +322,18 @@ impl<'tcx> LateLintPass<'tcx> for QuestionMark {
return;
}

if !in_constant(cx, stmt.hir_id) {
if !self.inside_try_block() && !in_constant(cx, stmt.hir_id) {
check_let_some_else_return_none(cx, stmt);
}
self.check_manual_let_else(cx, stmt);
}
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if !in_constant(cx, expr.hir_id) && is_lint_allowed(cx, QUESTION_MARK_USED, expr.hir_id) {
self.check_is_none_or_err_and_early_return(cx, expr);
self.check_if_let_some_or_err_and_early_return(cx, expr);
if !self.inside_try_block()
&& !in_constant(cx, expr.hir_id)
&& is_lint_allowed(cx, QUESTION_MARK_USED, expr.hir_id)
{
check_is_none_or_err_and_early_return(cx, expr);
check_if_let_some_or_err_and_early_return(cx, expr);
}
}

Expand Down
10 changes: 10 additions & 0 deletions tests/ui/manual_let_else.rs
View file
Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
#![feature(try_blocks)]
#![allow(unused_braces, unused_variables, dead_code)]
#![allow(
clippy::collapsible_else_if,
Expand Down Expand Up @@ -446,3 +447,12 @@ struct U<T> {
w: T,
x: T,
}

fn issue12337() {
// We want to generally silence question_mark lints within try blocks, since `?` has different
// behavior to `return`, and question_mark calls into manual_let_else logic, so make sure that
// we still emit a lint for manual_let_else
let _: Option<()> = try {
let v = if let Some(v_some) = g() { v_some } else { return };
};
}
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