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use rustc::hir;
use rustc::lint::*;
use syntax::ast;
use utils::{span_lint_and_then, snippet_opt, SpanlessEq, get_trait_def_id, implements_trait};
use utils::{higher, sugg};
declare_restriction_lint! {
pub ASSIGN_OPS,
"any compound assignment operation"
}
declare_lint! {
pub ASSIGN_OP_PATTERN,
Warn,
"assigning the result of an operation on a variable to that same variable"
}
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, MISREFACTORED_ASSIGN_OP)
}
}
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| {
let lhs = &sugg::Sugg::hir(cx, lhs, "..");
let rhs = &sugg::Sugg::hir(cx, rhs, "..");
db.span_suggestion(expr.span,
"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| {
let ty = cx.tcx.tables().expr_ty(assignee);
if ty.walk_shallow().next().is_some() {
return;
}
let rty = cx.tcx.tables().expr_ty(rhs);
if rty.walk_shallow().next().is_some() {
return;
}
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));
}
});
};
if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, l) {
lint(lhs, 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 {
let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
let ty = cx.tcx.tables().expr_ty(assignee);
if ty.walk_shallow().next().is_some() {
return;
}
let rty = cx.tcx.tables().expr_ty(rhs);
if rty.walk_shallow().next().is_some() {
return;
}
macro_rules! ops {
($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;
let path = [krate, module, concat!(stringify!($trait_name), "Assign")];
let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
trait_id
} else {
return;
};
let parent_fn = cx.tcx.map.get_parent(e.id);
let parent_impl = cx.tcx.map.get_parent(parent_fn);
if_let_chain!{[
parent_impl != ast::CRATE_NODE_ID,
let hir::map::Node::NodeItem(item) = cx.tcx.map.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, $ty, trait_id, vec![$rty])
},)*
_ => false,
}
}
}
if ops!(op.node,
cx,
ty,
rty,
Add: BiAdd,
Sub: BiSub,
Mul: BiMul,
Div: BiDiv,
Rem: BiRem,
And: BiAnd,
Or: BiOr,
BitAnd: BiBitAnd,
BitOr: BiBitOr,
BitXor: BiBitXor,
Shr: BiShr,
Shl: BiShl) {
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));
}
});
}
};
if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, l) {
lint(assignee, r);
}
if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, r) {
match op.node {
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,
}
}