use clippy_utils::diagnostics::{span_lint, span_lint_and_note};
use clippy_utils::{get_parent_expr, path_to_local, path_to_local_id};
-use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
+use if_chain::if_chain;
+use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_hir::{BinOpKind, Block, Expr, ExprKind, Guard, HirId, Local, Node, Stmt, StmtKind};
use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::hir::map::Map;
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
- /// **What it does:** Checks for a read and a write to the same variable where
+ /// ### What it does
+ /// Checks for a read and a write to the same variable where
/// whether the read occurs before or after the write depends on the evaluation
/// order of sub-expressions.
///
- /// **Why is this bad?** It is often confusing to read. In addition, the
- /// sub-expression evaluation order for Rust is not well documented.
+ /// ### Why is this bad?
+ /// It is often confusing to read. As described [here](https://doc.rust-lang.org/reference/expressions.html?highlight=subexpression#evaluation-order-of-operands),
+ /// the operands of these expressions are evaluated before applying the effects of the expression.
///
- /// **Known problems:** Code which intentionally depends on the evaluation
+ /// ### Known problems
+ /// Code which intentionally depends on the evaluation
/// order, or which is correct for any evaluation order.
///
- /// **Example:**
+ /// ### Example
/// ```rust
/// let mut x = 0;
///
/// };
/// let a = tmp + x;
/// ```
+ #[clippy::version = "pre 1.29.0"]
pub EVAL_ORDER_DEPENDENCE,
- complexity,
+ suspicious,
"whether a variable read occurs before a write depends on sub-expression evaluation order"
}
declare_clippy_lint! {
- /// **What it does:** Checks for diverging calls that are not match arms or
+ /// ### What it does
+ /// Checks for diverging calls that are not match arms or
/// statements.
///
- /// **Why is this bad?** It is often confusing to read. In addition, the
+ /// ### Why is this bad?
+ /// It is often confusing to read. In addition, the
/// sub-expression evaluation order for Rust is not well documented.
///
- /// **Known problems:** Someone might want to use `some_bool || panic!()` as a
+ /// ### Known problems
+ /// Someone might want to use `some_bool || panic!()` as a
/// shorthand.
///
- /// **Example:**
+ /// ### Example
/// ```rust,no_run
/// # fn b() -> bool { true }
/// # fn c() -> bool { true }
/// let x = (a, b, c, panic!());
/// // can simply be replaced by `panic!()`
/// ```
+ #[clippy::version = "pre 1.29.0"]
pub DIVERGING_SUB_EXPRESSION,
complexity,
"whether an expression contains a diverging sub expression"
impl<'tcx> LateLintPass<'tcx> for EvalOrderDependence {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// Find a write to a local variable.
- match expr.kind {
- ExprKind::Assign(lhs, ..) | ExprKind::AssignOp(_, lhs, _) => {
- if let Some(var) = path_to_local(lhs) {
- let mut visitor = ReadVisitor {
- cx,
- var,
- write_expr: expr,
- last_expr: expr,
- };
- check_for_unsequenced_reads(&mut visitor);
- }
- },
- _ => {},
- }
+ let var = if_chain! {
+ if let ExprKind::Assign(lhs, ..) | ExprKind::AssignOp(_, lhs, _) = expr.kind;
+ if let Some(var) = path_to_local(lhs);
+ if expr.span.desugaring_kind().is_none();
+ then { var } else { return; }
+ };
+ let mut visitor = ReadVisitor {
+ cx,
+ var,
+ write_expr: expr,
+ last_expr: expr,
+ };
+ check_for_unsequenced_reads(&mut visitor);
}
fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
match stmt.kind {
self.visit_expr(e);
for arm in arms {
if let Some(Guard::If(if_expr)) = arm.guard {
- self.visit_expr(if_expr)
+ self.visit_expr(if_expr);
}
// make sure top level arm expressions aren't linted
self.maybe_walk_expr(&*arm.body);
}
impl<'a, 'tcx> Visitor<'tcx> for DivergenceVisitor<'a, 'tcx> {
- type Map = Map<'tcx>;
-
fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
match e.kind {
ExprKind::Continue(_) | ExprKind::Break(_, _) | ExprKind::Ret(_) => self.report_diverging_sub_expr(e),
match typ.kind() {
ty::FnDef(..) | ty::FnPtr(_) => {
let sig = typ.fn_sig(self.cx.tcx);
- if let ty::Never = self.cx.tcx.erase_late_bound_regions(sig).output().kind() {
+ if self.cx.tcx.erase_late_bound_regions(sig).output().kind() == &ty::Never {
self.report_diverging_sub_expr(e);
}
},
fn visit_block(&mut self, _: &'tcx Block<'_>) {
// don't continue over blocks, LateLintPass already does that
}
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
- }
}
/// Walks up the AST from the given write expression (`vis.write_expr`) looking
}
impl<'a, 'tcx> Visitor<'tcx> for ReadVisitor<'a, 'tcx> {
- type Map = Map<'tcx>;
-
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if expr.hir_id == self.last_expr.hir_id {
return;
self.cx,
EVAL_ORDER_DEPENDENCE,
expr.span,
- "unsequenced read of a variable",
+ &format!("unsequenced read of `{}`", self.cx.tcx.hir().name(self.var)),
Some(self.write_expr.span),
"whether read occurs before this write depends on evaluation order",
);
walk_expr(self, expr);
}
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
- }
}
/// Returns `true` if `expr` is the LHS of an assignment, like `expr = ...`.
projects / rust.git / blobdiff