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Make expr_use_ctxt always return Some unless the syntax context changes.

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This commit is contained in:
Jason Newcomb 2023-11-14 22:41:38 -05:00
parent b587871e27
commit cdc4c697b5
7 changed files with 112 additions and 122 deletions
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176
clippy_utils/src/lib.rs
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@ -1,5 +1,6 @@
#![feature(array_chunks)]
#![feature(box_patterns)]
#![feature(control_flow_enum)]
#![feature(if_let_guard)]
#![feature(let_chains)]
#![feature(lint_reasons)]
@ -2508,26 +2509,30 @@ pub fn is_test_module_or_function(tcx: TyCtxt<'_>, item: &Item<'_>) -> bool {
&& item.ident.name.as_str().split('_').any(|a| a == "test" || a == "tests")
}
/// Walks the HIR tree from the given expression, up to the node where the value produced by the
/// expression is consumed. Calls the function for every node encountered this way until it returns
/// `Some`.
/// Walks up the HIR tree from the given expression in an attempt to find where the value is
/// consumed.
///
/// This allows walking through `if`, `match`, `break`, block expressions to find where the value
/// produced by the expression is consumed.
/// Termination has three conditions:
/// - The given function returns `Break`. This function will return the value.
/// - The consuming node is found. This function will return `Continue(use_node, child_id)`.
/// - No further parent nodes are found. This will trigger a debug assert or return `None`.
///
/// This allows walking through `if`, `match`, `break`, and block expressions to find where the
/// value produced by the expression is consumed.
pub fn walk_to_expr_usage<'tcx, T>(
cx: &LateContext<'tcx>,
e: &Expr<'tcx>,
mut f: impl FnMut(Node<'tcx>, HirId) -> Option<T>,
) -> Option<T> {
mut f: impl FnMut(HirId, Node<'tcx>, HirId) -> ControlFlow<T>,
) -> Option<ControlFlow<T, (Node<'tcx>, HirId)>> {
let map = cx.tcx.hir();
let mut iter = map.parent_iter(e.hir_id);
let mut child_id = e.hir_id;
while let Some((parent_id, parent)) = iter.next() {
if let Some(x) = f(parent, child_id) {
return Some(x);
if let ControlFlow::Break(x) = f(parent_id, parent, child_id) {
return Some(ControlFlow::Break(x));
}
let parent = match parent {
let parent_expr = match parent {
Node::Expr(e) => e,
Node::Block(Block { expr: Some(body), .. }) | Node::Arm(Arm { body, .. }) if body.hir_id == child_id => {
child_id = parent_id;
@ -2537,18 +2542,19 @@ pub fn walk_to_expr_usage<'tcx, T>(
child_id = parent_id;
continue;
},
_ => return None,
_ => return Some(ControlFlow::Continue((parent, child_id))),
};
match parent.kind {
match parent_expr.kind {
ExprKind::If(child, ..) | ExprKind::Match(child, ..) if child.hir_id != child_id => child_id = parent_id,
ExprKind::Break(Destination { target_id: Ok(id), .. }, _) => {
child_id = id;
iter = map.parent_iter(id);
},
ExprKind::Block(..) => child_id = parent_id,
_ => return None,
ExprKind::Block(..) | ExprKind::DropTemps(_) => child_id = parent_id,
_ => return Some(ControlFlow::Continue((parent, child_id))),
}
}
debug_assert!(false, "no parent node found for `{child_id:?}`");
None
}
@ -2592,6 +2598,8 @@ pub enum ExprUseNode<'tcx> {
Callee,
/// Access of a field.
FieldAccess(Ident),
Expr,
Other,
}
impl<'tcx> ExprUseNode<'tcx> {
/// Checks if the value is returned from the function.
@ -2668,144 +2676,104 @@ impl<'tcx> ExprUseNode<'tcx> {
let sig = cx.tcx.fn_sig(id).skip_binder();
Some(DefinedTy::Mir(cx.tcx.param_env(id).and(sig.input(i))))
},
Self::Local(_) | Self::FieldAccess(..) | Self::Callee => None,
Self::Local(_) | Self::FieldAccess(..) | Self::Callee | Self::Expr | Self::Other => None,
}
}
}
/// Gets the context an expression's value is used in.
#[expect(clippy::too_many_lines)]
pub fn expr_use_ctxt<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> Option<ExprUseCtxt<'tcx>> {
let mut adjustments = [].as_slice();
let mut is_ty_unified = false;
let mut moved_before_use = false;
let ctxt = e.span.ctxt();
walk_to_expr_usage(cx, e, &mut |parent, child_id| {
// LocalTableInContext returns the wrong lifetime, so go use `expr_adjustments` instead.
walk_to_expr_usage(cx, e, &mut |parent_id, parent, child_id| {
if adjustments.is_empty()
&& let Node::Expr(e) = cx.tcx.hir().get(child_id)
{
adjustments = cx.typeck_results().expr_adjustments(e);
}
match parent {
Node::Local(l) if l.span.ctxt() == ctxt => Some(ExprUseCtxt {
node: ExprUseNode::Local(l),
adjustments,
is_ty_unified,
moved_before_use,
}),
if !cx.tcx.hir().opt_span(parent_id).is_some_and(|x| x.ctxt() == ctxt) {
return ControlFlow::Break(());
}
if let Node::Expr(e) = parent {
match e.kind {
ExprKind::If(e, _, _) | ExprKind::Match(e, _, _) if e.hir_id != child_id => {
is_ty_unified = true;
moved_before_use = true;
},
ExprKind::Block(_, Some(_)) | ExprKind::Break(..) => {
is_ty_unified = true;
moved_before_use = true;
},
ExprKind::Block(..) => moved_before_use = true,
_ => {},
}
}
ControlFlow::Continue(())
})?
.continue_value()
.map(|(use_node, child_id)| {
let node = match use_node {
Node::Local(l) => ExprUseNode::Local(l),
Node::ExprField(field) => ExprUseNode::Field(field),
Node::Item(&Item {
kind: ItemKind::Static(..) | ItemKind::Const(..),
owner_id,
span,
..
})
| Node::TraitItem(&TraitItem {
kind: TraitItemKind::Const(..),
owner_id,
span,
..
})
| Node::ImplItem(&ImplItem {
kind: ImplItemKind::Const(..),
owner_id,
span,
..
}) if span.ctxt() == ctxt => Some(ExprUseCtxt {
node: ExprUseNode::ConstStatic(owner_id),
adjustments,
is_ty_unified,
moved_before_use,
}),
}) => ExprUseNode::ConstStatic(owner_id),
Node::Item(&Item {
kind: ItemKind::Fn(..),
owner_id,
span,
..
})
| Node::TraitItem(&TraitItem {
kind: TraitItemKind::Fn(..),
owner_id,
span,
..
})
| Node::ImplItem(&ImplItem {
kind: ImplItemKind::Fn(..),
owner_id,
span,
..
}) if span.ctxt() == ctxt => Some(ExprUseCtxt {
node: ExprUseNode::Return(owner_id),
adjustments,
is_ty_unified,
moved_before_use,
}),
}) => ExprUseNode::Return(owner_id),
Node::ExprField(field) if field.span.ctxt() == ctxt => Some(ExprUseCtxt {
node: ExprUseNode::Field(field),
adjustments,
is_ty_unified,
moved_before_use,
}),
Node::Expr(parent) if parent.span.ctxt() == ctxt => match parent.kind {
ExprKind::Ret(_) => Some(ExprUseCtxt {
node: ExprUseNode::Return(OwnerId {
def_id: cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()),
}),
adjustments,
is_ty_unified,
moved_before_use,
Node::Expr(use_expr) => match use_expr.kind {
ExprKind::Ret(_) => ExprUseNode::Return(OwnerId {
def_id: cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()),
}),
ExprKind::Closure(closure) => Some(ExprUseCtxt {
node: ExprUseNode::Return(OwnerId { def_id: closure.def_id }),
adjustments,
is_ty_unified,
moved_before_use,
}),
ExprKind::Call(func, args) => Some(ExprUseCtxt {
node: match args.iter().position(|arg| arg.hir_id == child_id) {
Some(i) => ExprUseNode::FnArg(func, i),
None => ExprUseNode::Callee,
},
adjustments,
is_ty_unified,
moved_before_use,
}),
ExprKind::MethodCall(name, _, args, _) => Some(ExprUseCtxt {
node: ExprUseNode::MethodArg(
parent.hir_id,
name.args,
args.iter().position(|arg| arg.hir_id == child_id).map_or(0, |i| i + 1),
),
adjustments,
is_ty_unified,
moved_before_use,
}),
ExprKind::Field(child, name) if child.hir_id == e.hir_id => Some(ExprUseCtxt {
node: ExprUseNode::FieldAccess(name),
adjustments,
is_ty_unified,
moved_before_use,
}),
ExprKind::If(e, _, _) | ExprKind::Match(e, _, _) if e.hir_id != child_id => {
is_ty_unified = true;
moved_before_use = true;
None
ExprKind::Closure(closure) => ExprUseNode::Return(OwnerId { def_id: closure.def_id }),
ExprKind::Call(func, args) => match args.iter().position(|arg| arg.hir_id == child_id) {
Some(i) => ExprUseNode::FnArg(func, i),
None => ExprUseNode::Callee,
},
ExprKind::Block(_, Some(_)) | ExprKind::Break(..) => {
is_ty_unified = true;
moved_before_use = true;
None
},
ExprKind::Block(..) => {
moved_before_use = true;
None
},
_ => None,
ExprKind::MethodCall(name, _, args, _) => ExprUseNode::MethodArg(
use_expr.hir_id,
name.args,
args.iter().position(|arg| arg.hir_id == child_id).map_or(0, |i| i + 1),
),
ExprKind::Field(child, name) if child.hir_id == e.hir_id => ExprUseNode::FieldAccess(name),
_ => ExprUseNode::Expr,
},
_ => None,
_ => ExprUseNode::Other,
};
ExprUseCtxt {
node,
adjustments,
is_ty_unified,
moved_before_use,
}
})
}