use rustc::lint::*;
use rustc::ty;
use rustc::hir;
use syntax::ast::RangeLimits;
use utils::{self, higher};
use utils::higher::Range;
use consts::{constant, Constant};
declare_clippy_lint! {
pub OUT_OF_BOUNDS_INDEXING,
correctness,
"out of bounds constant indexing"
}
declare_clippy_lint! {
pub INDEXING_SLICING,
restriction,
"indexing/slicing usage"
}
#[derive(Copy, Clone)]
pub struct ArrayIndexing;
impl LintPass for ArrayIndexing {
fn get_lints(&self) -> LintArray {
lint_array!(INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ArrayIndexing {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx hir::Expr) {
if let hir::ExprIndex(ref array, ref index) = e.node {
let ty = cx.tables.expr_ty(array);
if let ty::TyArray(_, size) = ty.sty {
let size = size.assert_usize(cx.tcx).unwrap().into();
if let Some((Constant::Int(const_index), _)) = constant(cx, index) {
if size <= const_index {
utils::span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "const index is out of bounds");
}
return;
}
if let Some(range) = higher::range(cx, index) {
if let Some((start, end)) = to_const_range(cx, range, size) {
if start > size || end > size {
utils::span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "range is out of bounds");
}
return;
}
}
}
if let Some(range) = higher::range(cx, index) {
if range.start.is_none() && range.end.is_none() {
return;
}
utils::span_lint(cx, INDEXING_SLICING, e.span, "slicing may panic");
} else {
utils::span_lint(cx, INDEXING_SLICING, e.span, "indexing may panic");
}
}
}
}
fn to_const_range<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, range: Range, array_size: u128) -> Option<(u128, u128)> {
let s = range.start.map(|expr| constant(cx, expr).map(|(c, _)| c));
let start = match s {
Some(Some(Constant::Int(x))) => x,
Some(_) => return None,
None => 0,
};
let e = range.end.map(|expr| constant(cx, expr).map(|(c, _)| c));
let end = match e {
Some(Some(Constant::Int(x))) => if range.limits == RangeLimits::Closed {
x + 1
} else {
x
},
Some(_) => return None,
None => array_size,
};
Some((start, end))
}