266 lines
11 KiB
Rust
266 lines
11 KiB
Rust
use rustc::hir;
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use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
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use rustc::lint::*;
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use syntax::ast;
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use utils::{get_trait_def_id, implements_trait, snippet_opt, span_lint_and_then, SpanlessEq};
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use utils::{higher, sugg};
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/// **What it does:** Checks for compound assignment operations (`+=` and
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/// similar).
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///
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/// **Why is this bad?** Projects with many developers from languages without
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/// those operations may find them unreadable and not worth their weight.
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///
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/// **Known problems:** Types implementing `OpAssign` don't necessarily
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/// implement `Op`.
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///
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/// **Example:**
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/// ```rust
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/// a += 1;
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/// ```
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declare_restriction_lint! {
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pub ASSIGN_OPS,
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"any compound assignment operation"
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}
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/// **What it does:** Checks for `a = a op b` or `a = b commutative_op a`
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/// patterns.
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///
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/// **Why is this bad?** These can be written as the shorter `a op= b`.
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///
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/// **Known problems:** While forbidden by the spec, `OpAssign` traits may have
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/// implementations that differ from the regular `Op` impl.
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///
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/// **Example:**
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/// ```rust
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/// let mut a = 5;
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/// ...
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/// a = a + b;
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/// ```
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declare_lint! {
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pub ASSIGN_OP_PATTERN,
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Warn,
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"assigning the result of an operation on a variable to that same variable"
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}
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/// **What it does:** Checks for `a op= a op b` or `a op= b op a` patterns.
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///
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/// **Why is this bad?** Most likely these are bugs where one meant to write `a
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/// op= b`.
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///
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/// **Known problems:** Someone might actually mean `a op= a op b`, but that
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/// should rather be written as `a = (2 * a) op b` where applicable.
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///
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/// **Example:**
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/// ```rust
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/// let mut a = 5;
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/// ...
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/// a += a + b;
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/// ```
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declare_lint! {
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pub MISREFACTORED_ASSIGN_OP,
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Warn,
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"having a variable on both sides of an assign op"
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}
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#[derive(Copy, Clone, Default)]
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pub struct AssignOps;
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impl LintPass for AssignOps {
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fn get_lints(&self) -> LintArray {
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lint_array!(ASSIGN_OPS, ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
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match expr.node {
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hir::ExprAssignOp(op, ref lhs, ref rhs) => {
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span_lint_and_then(cx, ASSIGN_OPS, expr.span, "assign operation detected", |db| {
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let lhs = &sugg::Sugg::hir(cx, lhs, "..");
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let rhs = &sugg::Sugg::hir(cx, rhs, "..");
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db.span_suggestion(
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expr.span,
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"replace it with",
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format!("{} = {}", lhs, sugg::make_binop(higher::binop(op.node), lhs, rhs)),
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);
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});
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if let hir::ExprBinary(binop, ref l, ref r) = rhs.node {
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if op.node == binop.node {
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let lint = |assignee: &hir::Expr, rhs_other: &hir::Expr| {
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span_lint_and_then(
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cx,
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MISREFACTORED_ASSIGN_OP,
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expr.span,
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"variable appears on both sides of an assignment operation",
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|db| if let (Some(snip_a), Some(snip_r)) =
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(snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span))
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{
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let a = &sugg::Sugg::hir(cx, assignee, "..");
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let r = &sugg::Sugg::hir(cx, rhs, "..");
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let long = format!("{} = {}", snip_a, sugg::make_binop(higher::binop(op.node), a, r));
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db.span_suggestion(
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expr.span,
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&format!("Did you mean {} = {} {} {} or {}? Consider replacing it with",
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snip_a, snip_a, op.node.as_str(), snip_r,
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long),
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format!("{} {}= {}", snip_a, op.node.as_str(), snip_r)
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);
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db.span_suggestion(
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expr.span,
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"or",
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long
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);
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},
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);
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};
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// lhs op= l op r
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if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, l) {
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lint(lhs, r);
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}
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// lhs op= l commutative_op r
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if is_commutative(op.node) && SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, r) {
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lint(lhs, l);
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}
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}
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}
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},
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hir::ExprAssign(ref assignee, ref e) => {
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if let hir::ExprBinary(op, ref l, ref r) = e.node {
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#[allow(cyclomatic_complexity)]
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let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
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let ty = cx.tables.expr_ty(assignee);
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let rty = cx.tables.expr_ty(rhs);
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macro_rules! ops {
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($op:expr,
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$cx:expr,
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$ty:expr,
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$rty:expr,
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$($trait_name:ident:$full_trait_name:ident),+) => {
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match $op {
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$(hir::$full_trait_name => {
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let [krate, module] = ::utils::paths::OPS_MODULE;
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let path = [krate, module, concat!(stringify!($trait_name), "Assign")];
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let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
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trait_id
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} else {
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return; // useless if the trait doesn't exist
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};
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// check that we are not inside an `impl AssignOp` of this exact operation
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let parent_fn = cx.tcx.hir.get_parent(e.id);
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let parent_impl = cx.tcx.hir.get_parent(parent_fn);
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// the crate node is the only one that is not in the map
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if_chain! {
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if parent_impl != ast::CRATE_NODE_ID;
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if let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl);
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if let hir::Item_::ItemImpl(_, _, _, _, Some(ref trait_ref), _, _) =
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item.node;
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if trait_ref.path.def.def_id() == trait_id;
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then { return; }
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}
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implements_trait($cx, $ty, trait_id, &[$rty])
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},)*
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_ => false,
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}
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}
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}
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if ops!(
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op.node,
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cx,
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ty,
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rty,
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Add: BiAdd,
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Sub: BiSub,
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Mul: BiMul,
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Div: BiDiv,
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Rem: BiRem,
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And: BiAnd,
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Or: BiOr,
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BitAnd: BiBitAnd,
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BitOr: BiBitOr,
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BitXor: BiBitXor,
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Shr: BiShr,
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Shl: BiShl
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) {
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span_lint_and_then(
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cx,
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ASSIGN_OP_PATTERN,
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expr.span,
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"manual implementation of an assign operation",
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|db| if let (Some(snip_a), Some(snip_r)) =
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(snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
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{
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db.span_suggestion(
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expr.span,
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"replace it with",
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format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
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);
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},
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);
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}
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};
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let mut visitor = ExprVisitor {
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assignee: assignee,
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counter: 0,
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cx: cx
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};
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walk_expr(&mut visitor, e);
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if visitor.counter == 1 {
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// a = a op b
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if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, l) {
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lint(assignee, r);
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}
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// a = b commutative_op a
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if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, r) {
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match op.node {
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hir::BiAdd |
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hir::BiMul |
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hir::BiAnd |
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hir::BiOr |
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hir::BiBitXor |
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hir::BiBitAnd |
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hir::BiBitOr => {
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lint(assignee, l);
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},
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_ => {},
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}
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}
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}
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}
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},
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_ => {},
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}
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}
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}
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fn is_commutative(op: hir::BinOp_) -> bool {
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use rustc::hir::BinOp_::*;
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match op {
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BiAdd | BiMul | BiAnd | BiOr | BiBitXor | BiBitAnd | BiBitOr | BiEq | BiNe => true,
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BiSub | BiDiv | BiRem | BiShl | BiShr | BiLt | BiLe | BiGe | BiGt => false,
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}
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}
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struct ExprVisitor<'a, 'tcx: 'a> {
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assignee: &'a hir::Expr,
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counter: u8,
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cx: &'a LateContext<'a, 'tcx>,
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}
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impl<'a, 'tcx: 'a> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
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if SpanlessEq::new(self.cx).ignore_fn().eq_expr(self.assignee, &expr) {
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self.counter += 1;
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}
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walk_expr(self, expr);
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}
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::None
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}
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}
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