use rustc::lint::*;
use rustc::hir::*;
use syntax::codemap::Spanned;
use utils::{is_integer_literal, paths, snippet, span_lint};
use utils::{higher, implements_trait, get_trait_def_id};
declare_lint! {
pub ITERATOR_STEP_BY_ZERO,
Warn,
"using `Iterator::step_by(0)`, which produces an infinite iterator"
}
declare_lint! {
pub RANGE_ZIP_WITH_LEN,
Warn,
"zipping iterator with a range when `enumerate()` would do"
}
#[derive(Copy,Clone)]
pub struct StepByZero;
impl LintPass for StepByZero {
fn get_lints(&self) -> LintArray {
lint_array!(ITERATOR_STEP_BY_ZERO, RANGE_ZIP_WITH_LEN)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for StepByZero {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if let ExprMethodCall(Spanned { node: ref name, .. }, _, ref args) = expr.node {
let name = name.as_str();
if name == "step_by" && args.len() == 2 && has_step_by(cx, &args[0]) {
use consts::{Constant, constant};
use rustc_const_math::ConstInt::Usize;
if let Some((Constant::Int(Usize(us)), _)) = constant(cx, &args[1]) {
if us.as_u64(cx.sess().target.uint_type) == 0 {
span_lint(cx,
ITERATOR_STEP_BY_ZERO,
expr.span,
"Iterator::step_by(0) will panic at runtime");
}
}
} else if name == "zip" && args.len() == 2 {
let iter = &args[0].node;
let zip_arg = &args[1];
if_let_chain! {[
let ExprMethodCall( Spanned { node: iter_name, .. }, _, ref iter_args ) = *iter,
iter_name == "iter",
let Some(higher::Range { start: Some(start), end: Some(end), .. }) = higher::range(zip_arg),
is_integer_literal(start, 0),
let ExprMethodCall(Spanned { node: len_name, .. }, _, ref len_args) = end.node,
len_name == "len" && len_args.len() == 1,
let ExprPath(QPath::Resolved(_, ref iter_path)) = iter_args[0].node,
let ExprPath(QPath::Resolved(_, ref len_path)) = len_args[0].node,
iter_path.segments == len_path.segments
], {
span_lint(cx,
RANGE_ZIP_WITH_LEN,
expr.span,
&format!("It is more idiomatic to use {}.iter().enumerate()",
snippet(cx, iter_args[0].span, "_")));
}}
}
}
}
}
fn has_step_by(cx: &LateContext, expr: &Expr) -> bool {
let ty = cx.tables.expr_ty_adjusted(expr);
get_trait_def_id(cx, &paths::ITERATOR).map_or(false, |iterator_trait| implements_trait(cx, ty, iterator_trait, &[]))
}