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use reexport::*;
use rustc::hir::*;
use rustc::hir::intravisit::FnKind;
use rustc::lint::*;
use rustc::middle::const_val::ConstVal;
use rustc::ty;
use rustc_const_eval::EvalHint::ExprTypeChecked;
use rustc_const_eval::eval_const_expr_partial;
use rustc_const_math::ConstFloat;
use syntax::codemap::{Span, Spanned, ExpnFormat};
use utils::{get_item_name, get_parent_expr, implements_trait, in_macro, is_integer_literal, match_path, snippet,
span_lint, span_lint_and_then, walk_ptrs_ty, last_path_segment, iter_input_pats};
use utils::sugg::Sugg;
declare_lint! {
pub TOPLEVEL_REF_ARG,
Warn,
"an entire binding declared as `ref`, in a function argument or a `let` statement"
}
declare_lint! {
pub CMP_NAN,
Deny,
"comparisons to NAN, which will always return false, probably not intended"
}
declare_lint! {
pub FLOAT_CMP,
Warn,
"using `==` or `!=` on float values instead of comparing difference with an epsilon"
}
declare_lint! {
pub CMP_OWNED,
Warn,
"creating owned instances for comparing with others, e.g. `x == \"foo\".to_string()`"
}
declare_lint! {
pub MODULO_ONE,
Warn,
"taking a number modulo 1, which always returns 0"
}
declare_lint! {
pub REDUNDANT_PATTERN,
Warn,
"using `name @ _` in a pattern"
}
declare_lint! {
pub USED_UNDERSCORE_BINDING,
Allow,
"using a binding which is prefixed with an underscore"
}
declare_lint! {
pub SHORT_CIRCUIT_STATEMENT,
Warn,
"using a short circuit boolean condition as a statement"
}
#[derive(Copy, Clone)]
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(TOPLEVEL_REF_ARG,
CMP_NAN,
FLOAT_CMP,
CMP_OWNED,
MODULO_ONE,
REDUNDANT_PATTERN,
USED_UNDERSCORE_BINDING,
SHORT_CIRCUIT_STATEMENT)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_fn(
&mut self,
cx: &LateContext<'a, 'tcx>,
k: FnKind<'tcx>,
decl: &'tcx FnDecl,
body: &'tcx Body,
_: Span,
_: NodeId
) {
if let FnKind::Closure(_) = k {
return;
}
for arg in iter_input_pats(decl, body) {
if let PatKind::Binding(BindByRef(_), _, _, _) = arg.pat.node {
span_lint(cx,
TOPLEVEL_REF_ARG,
arg.pat.span,
"`ref` directly on a function argument is ignored. Consider using a reference type instead.");
}
}
}
fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, s: &'tcx Stmt) {
if_let_chain! {[
let StmtDecl(ref d, _) = s.node,
let DeclLocal(ref l) = d.node,
let PatKind::Binding(BindByRef(mt), _, i, None) = l.pat.node,
let Some(ref init) = l.init
], {
let init = Sugg::hir(cx, init, "..");
let (mutopt,initref) = if mt == Mutability::MutMutable {
("mut ", init.mut_addr())
} else {
("", init.addr())
};
let tyopt = if let Some(ref ty) = l.ty {
format!(": &{mutopt}{ty}", mutopt=mutopt, ty=snippet(cx, ty.span, "_"))
} else {
"".to_owned()
};
span_lint_and_then(cx,
TOPLEVEL_REF_ARG,
l.pat.span,
"`ref` on an entire `let` pattern is discouraged, take a reference with `&` instead",
|db| {
db.span_suggestion(s.span,
"try",
format!("let {name}{tyopt} = {initref};",
name=snippet(cx, i.span, "_"),
tyopt=tyopt,
initref=initref));
}
);
}};
if_let_chain! {[
let StmtSemi(ref expr, _) = s.node,
let Expr_::ExprBinary(ref binop, ref a, ref b) = expr.node,
binop.node == BiAnd || binop.node == BiOr,
let Some(sugg) = Sugg::hir_opt(cx, a),
], {
span_lint_and_then(cx,
SHORT_CIRCUIT_STATEMENT,
s.span,
"boolean short circuit operator in statement may be clearer using an explicit test",
|db| {
let sugg = if binop.node == BiOr { !sugg } else { sugg };
db.span_suggestion(s.span, "replace it with",
format!("if {} {{ {}; }}", sugg, &snippet(cx, b.span, "..")));
});
}};
}
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if let ExprBinary(ref cmp, ref left, ref right) = expr.node {
let op = cmp.node;
if op.is_comparison() {
if let ExprPath(QPath::Resolved(_, ref path)) = left.node {
check_nan(cx, path, expr.span);
}
if let ExprPath(QPath::Resolved(_, ref path)) = right.node {
check_nan(cx, path, expr.span);
}
check_to_owned(cx, left, right, true, cmp.span);
check_to_owned(cx, right, left, false, cmp.span)
}
if (op == BiEq || op == BiNe) && (is_float(cx, left) || is_float(cx, right)) {
if is_allowed(cx, left) || is_allowed(cx, right) {
return;
}
if let Some(name) = get_item_name(cx, expr) {
let name = &*name.as_str();
if name == "eq" || name == "ne" || name == "is_nan" || name.starts_with("eq_") ||
name.ends_with("_eq") {
return;
}
}
span_lint_and_then(cx, FLOAT_CMP, expr.span, "strict comparison of f32 or f64", |db| {
let lhs = Sugg::hir(cx, left, "..");
let rhs = Sugg::hir(cx, right, "..");
db.span_suggestion(expr.span,
"consider comparing them within some error",
format!("({}).abs() < error", lhs - rhs));
db.span_note(expr.span, "std::f32::EPSILON and std::f64::EPSILON are available.");
});
} else if op == BiRem && is_integer_literal(right, 1) {
span_lint(cx, MODULO_ONE, expr.span, "any number modulo 1 will be 0");
}
}
if in_attributes_expansion(cx, expr) {
return;
}
let binding = match expr.node {
ExprPath(ref qpath) => {
let binding = last_path_segment(qpath).name.as_str();
if binding.starts_with('_') &&
!binding.starts_with("__") &&
&*binding != "_result" &&
is_used(cx, expr) &&
non_macro_local(cx, &cx.tcx.tables().qpath_def(qpath, expr.id)) {
Some(binding)
} else {
None
}
},
ExprField(_, spanned) => {
let name = spanned.node.as_str();
if name.starts_with('_') && !name.starts_with("__") {
Some(name)
} else {
None
}
},
_ => None,
};
if let Some(binding) = binding {
span_lint(cx,
USED_UNDERSCORE_BINDING,
expr.span,
&format!("used binding `{}` which is prefixed with an underscore. A leading \
underscore signals that a binding will not be used.",
binding));
}
}
fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat) {
if let PatKind::Binding(_, _, ref ident, Some(ref right)) = pat.node {
if right.node == PatKind::Wild {
span_lint(cx,
REDUNDANT_PATTERN,
pat.span,
&format!("the `{} @ _` pattern can be written as just `{}`", ident.node, ident.node));
}
}
}
}
fn check_nan(cx: &LateContext, path: &Path, span: Span) {
path.segments.last().map(|seg| {
if &*seg.name.as_str() == "NAN" {
span_lint(cx,
CMP_NAN,
span,
"doomed comparison with NAN, use `std::{f32,f64}::is_nan()` instead");
}
});
}
fn is_allowed(cx: &LateContext, expr: &Expr) -> bool {
let res = eval_const_expr_partial(cx.tcx, expr, ExprTypeChecked, None);
if let Ok(ConstVal::Float(val)) = res {
use std::cmp::Ordering;
let zero = ConstFloat::FInfer {
f32: 0.0,
f64: 0.0,
};
let infinity = ConstFloat::FInfer {
f32: ::std::f32::INFINITY,
f64: ::std::f64::INFINITY,
};
let neg_infinity = ConstFloat::FInfer {
f32: ::std::f32::NEG_INFINITY,
f64: ::std::f64::NEG_INFINITY,
};
val.try_cmp(zero) == Ok(Ordering::Equal) || val.try_cmp(infinity) == Ok(Ordering::Equal) ||
val.try_cmp(neg_infinity) == Ok(Ordering::Equal)
} else {
false
}
}
fn is_float(cx: &LateContext, expr: &Expr) -> bool {
matches!(walk_ptrs_ty(cx.tcx.tables().expr_ty(expr)).sty, ty::TyFloat(_))
}
fn check_to_owned(cx: &LateContext, expr: &Expr, other: &Expr, left: bool, op: Span) {
let (arg_ty, snip) = match expr.node {
ExprMethodCall(Spanned { node: ref name, .. }, _, ref args) if args.len() == 1 => {
let name = &*name.as_str();
if name == "to_string" || name == "to_owned" && is_str_arg(cx, args) {
(cx.tcx.tables().expr_ty(&args[0]), snippet(cx, args[0].span, ".."))
} else {
return;
}
},
ExprCall(ref path, ref v) if v.len() == 1 => {
if let ExprPath(ref path) = path.node {
if match_path(path, &["String", "from_str"]) || match_path(path, &["String", "from"]) {
(cx.tcx.tables().expr_ty(&v[0]), snippet(cx, v[0].span, ".."))
} else {
return;
}
} else {
return;
}
},
_ => return,
};
let other_ty = cx.tcx.tables().expr_ty(other);
let partial_eq_trait_id = match cx.tcx.lang_items.eq_trait() {
Some(id) => id,
None => return,
};
if !implements_trait(cx, arg_ty, partial_eq_trait_id, vec![other_ty]) {
return;
}
if left {
span_lint(cx,
CMP_OWNED,
expr.span,
&format!("this creates an owned instance just for comparison. Consider using `{} {} {}` to \
compare without allocation",
snip,
snippet(cx, op, "=="),
snippet(cx, other.span, "..")));
} else {
span_lint(cx,
CMP_OWNED,
expr.span,
&format!("this creates an owned instance just for comparison. Consider using `{} {} {}` to \
compare without allocation",
snippet(cx, other.span, ".."),
snippet(cx, op, "=="),
snip));
}
}
fn is_str_arg(cx: &LateContext, args: &[Expr]) -> bool {
args.len() == 1 && matches!(walk_ptrs_ty(cx.tcx.tables().expr_ty(&args[0])).sty, ty::TyStr)
}
fn is_used(cx: &LateContext, expr: &Expr) -> bool {
if let Some(parent) = get_parent_expr(cx, expr) {
match parent.node {
ExprAssign(_, ref rhs) |
ExprAssignOp(_, _, ref rhs) => **rhs == *expr,
_ => is_used(cx, parent),
}
} else {
true
}
}
fn in_attributes_expansion(cx: &LateContext, expr: &Expr) -> bool {
cx.sess().codemap().with_expn_info(expr.span.expn_id, |info_opt| {
info_opt.map_or(false, |info| matches!(info.callee.format, ExpnFormat::MacroAttribute(_)))
})
}
fn non_macro_local(cx: &LateContext, def: &def::Def) -> bool {
match *def {
def::Def::Local(id) |
def::Def::Upvar(id, _, _) => {
if let Some(span) = cx.tcx.map.span_if_local(id) {
!in_macro(cx, span)
} else {
true
}
},
_ => false,
}
}