use rustc::hir;
use rustc::lint::*;
-use utils::{span_lint_and_then, span_lint, snippet_opt, SpanlessEq, get_trait_def_id, implements_trait};
+use syntax::ast;
+use utils::{span_lint_and_then, snippet_opt, SpanlessEq, get_trait_def_id, implements_trait};
use utils::{higher, sugg};
-/// **What it does:** This lint checks for `+=` operations and similar.
+/// **What it does:** Checks for compound assignment operations (`+=` and similar).
///
-/// **Why is this bad?** Projects with many developers from languages without those operations may
-/// find them unreadable and not worth their weight.
+/// **Why is this bad?** Projects with many developers from languages without
+/// those operations may find them unreadable and not worth their weight.
///
/// **Known problems:** Types implementing `OpAssign` don't necessarily implement `Op`.
///
/// **Example:**
-/// ```
+/// ```rust
/// a += 1;
/// ```
declare_restriction_lint! {
pub ASSIGN_OPS,
- "any assignment operation"
+ "any compound assignment operation"
}
-/// **What it does:** Check for `a = a op b` or `a = b commutative_op a` patterns.
+/// **What it does:** Checks for `a = a op b` or `a = b commutative_op a` patterns.
///
/// **Why is this bad?** These can be written as the shorter `a op= b`.
///
-/// **Known problems:** While forbidden by the spec, `OpAssign` traits may have implementations that differ from the regular `Op` impl.
+/// **Known problems:** While forbidden by the spec, `OpAssign` traits may have
+/// implementations that differ from the regular `Op` impl.
///
/// **Example:**
-///
-/// ```
+/// ```rust
/// let mut a = 5;
/// ...
/// a = a + b;
"assigning the result of an operation on a variable to that same variable"
}
+/// **What it does:** Checks for `a op= a op b` or `a op= b op a` patterns.
+///
+/// **Why is this bad?** Most likely these are bugs where one meant to write `a op= b`.
+///
+/// **Known problems:** Someone might actually mean `a op= a op b`, but that
+/// should rather be written as `a = (2 * a) op b` where applicable.
+///
+/// **Example:**
+/// ```rust
+/// let mut a = 5;
+/// ...
+/// a += a + b;
+/// ```
+declare_lint! {
+ pub MISREFACTORED_ASSIGN_OP,
+ Warn,
+ "having a variable on both sides of an assign op"
+}
+
#[derive(Copy, Clone, Default)]
pub struct AssignOps;
impl LintPass for AssignOps {
fn get_lints(&self) -> LintArray {
- lint_array!(ASSIGN_OPS, ASSIGN_OP_PATTERN)
+ lint_array!(ASSIGN_OPS, ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP)
}
}
-impl LateLintPass for AssignOps {
- fn check_expr(&mut self, cx: &LateContext, expr: &hir::Expr) {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
match expr.node {
hir::ExprAssignOp(op, ref lhs, ref rhs) => {
span_lint_and_then(cx, ASSIGN_OPS, expr.span, "assign operation detected", |db| {
"replace it with",
format!("{} = {}", lhs, sugg::make_binop(higher::binop(op.node), lhs, rhs)));
});
- }
+ if let hir::ExprBinary(binop, ref l, ref r) = rhs.node {
+ if op.node == binop.node {
+ let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
+ span_lint_and_then(cx,
+ MISREFACTORED_ASSIGN_OP,
+ expr.span,
+ "variable appears on both sides of an assignment operation",
+ |db| if let (Some(snip_a), Some(snip_r)) =
+ (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span)) {
+ db.span_suggestion(expr.span,
+ "replace it with",
+ format!("{} {}= {}",
+ snip_a,
+ op.node.as_str(),
+ snip_r));
+ });
+ };
+ // lhs op= l op r
+ if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, l) {
+ lint(lhs, r);
+ }
+ // lhs op= l commutative_op r
+ if is_commutative(op.node) && SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, r) {
+ lint(lhs, l);
+ }
+ }
+ }
+ },
hir::ExprAssign(ref assignee, ref e) => {
if let hir::ExprBinary(op, ref l, ref r) = e.node {
+ #[allow(cyclomatic_complexity)]
let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
- let ty = cx.tcx.expr_ty(assignee);
- if ty.walk_shallow().next().is_some() {
- return; // implements_trait does not work with generics
- }
- let rty = cx.tcx.expr_ty(rhs);
- if rty.walk_shallow().next().is_some() {
- return; // implements_trait does not work with generics
- }
+ let ty = cx.tables.expr_ty(assignee);
+ let rty = cx.tables.expr_ty(rhs);
macro_rules! ops {
- ($op:expr, $cx:expr, $ty:expr, $rty:expr, $($trait_name:ident:$full_trait_name:ident),+) => {
+ ($op:expr,
+ $cx:expr,
+ $ty:expr,
+ $rty:expr,
+ $($trait_name:ident:$full_trait_name:ident),+) => {
match $op {
$(hir::$full_trait_name => {
let [krate, module] = ::utils::paths::OPS_MODULE;
} else {
return; // useless if the trait doesn't exist
};
- implements_trait($cx, $ty, trait_id, vec![$rty])
+ // check that we are not inside an `impl AssignOp` of this exact operation
+ let parent_fn = cx.tcx.hir.get_parent(e.id);
+ let parent_impl = cx.tcx.hir.get_parent(parent_fn);
+ // the crate node is the only one that is not in the map
+ if_let_chain!{[
+ parent_impl != ast::CRATE_NODE_ID,
+ let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl),
+ let hir::Item_::ItemImpl(_, _, _, _, Some(ref trait_ref), _, _) = item.node,
+ trait_ref.path.def.def_id() == trait_id
+ ], { return; }}
+ implements_trait($cx, $ty, trait_id, &[$rty])
},)*
_ => false,
}
BitXor: BiBitXor,
Shr: BiShr,
Shl: BiShl) {
- if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span),
- snippet_opt(cx, rhs.span)) {
- span_lint_and_then(cx,
- ASSIGN_OP_PATTERN,
- expr.span,
- "manual implementation of an assign operation",
- |db| {
- db.span_suggestion(expr.span,
- "replace it with",
- format!("{} {}= {}", snip_a, op.node.as_str(), snip_r));
- });
- } else {
- span_lint(cx,
- ASSIGN_OP_PATTERN,
- expr.span,
- "manual implementation of an assign operation");
- }
+ span_lint_and_then(cx,
+ ASSIGN_OP_PATTERN,
+ expr.span,
+ "manual implementation of an assign operation",
+ |db| if let (Some(snip_a), Some(snip_r)) =
+ (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span)) {
+ db.span_suggestion(expr.span,
+ "replace it with",
+ format!("{} {}= {}",
+ snip_a,
+ op.node.as_str(),
+ snip_r));
+ });
}
};
// a = a op b
hir::BiAdd | hir::BiMul | hir::BiAnd | hir::BiOr | hir::BiBitXor | hir::BiBitAnd |
hir::BiBitOr => {
lint(assignee, l);
- }
- _ => {}
+ },
+ _ => {},
}
}
}
- }
- _ => {}
+ },
+ _ => {},
}
}
}
+
+fn is_commutative(op: hir::BinOp_) -> bool {
+ use rustc::hir::BinOp_::*;
+ match op {
+ BiAdd | BiMul | BiAnd | BiOr | BiBitXor | BiBitAnd | BiBitOr | BiEq | BiNe => true,
+ BiSub | BiDiv | BiRem | BiShl | BiShr | BiLt | BiLe | BiGe | BiGt => false,
+ }
+}
projects / rust.git / blobdiff