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use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{get_parent_expr, path_to_local_id, usage};
use if_chain::if_chain;
use rustc_ast::ast;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_hir::{BorrowKind, Expr, ExprKind, HirId, Mutability, Pat};
use rustc_lint::LateContext;
use rustc_middle::hir::nested_filter;
use rustc_middle::ty::{self, Ty};
use rustc_span::symbol::sym;
pub(super) fn derefs_to_slice<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx hir::Expr<'tcx>,
ty: Ty<'tcx>,
) -> Option<&'tcx hir::Expr<'tcx>> {
fn may_slice<'a>(cx: &LateContext<'a>, ty: Ty<'a>) -> bool {
match ty.kind() {
ty::Slice(_) => true,
ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
ty::Adt(..) => is_type_diagnostic_item(cx, ty, sym::Vec),
ty::Array(_, size) => size.try_eval_target_usize(cx.tcx, cx.param_env).is_some(),
ty::Ref(_, inner, _) => may_slice(cx, *inner),
_ => false,
}
}
if let hir::ExprKind::MethodCall(path, self_arg, ..) = &expr.kind {
if path.ident.name == sym::iter && may_slice(cx, cx.typeck_results().expr_ty(self_arg)) {
Some(self_arg)
} else {
None
}
} else {
match ty.kind() {
ty::Slice(_) => Some(expr),
ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
ty::Ref(_, inner, _) => {
if may_slice(cx, *inner) {
Some(expr)
} else {
None
}
},
_ => None,
}
}
}
pub(super) fn get_hint_if_single_char_arg(
cx: &LateContext<'_>,
arg: &hir::Expr<'_>,
applicability: &mut Applicability,
) -> Option<String> {
if_chain! {
if let hir::ExprKind::Lit(lit) = &arg.kind;
if let ast::LitKind::Str(r, style) = lit.node;
let string = r.as_str();
if string.chars().count() == 1;
then {
let snip = snippet_with_applicability(cx, arg.span, string, applicability);
let ch = if let ast::StrStyle::Raw(nhash) = style {
let nhash = nhash as usize;
// for raw string: r##"a"##
&snip[(nhash + 2)..(snip.len() - 1 - nhash)]
} else {
// for regular string: "a"
&snip[1..(snip.len() - 1)]
};
let hint = format!("'{}'", match ch {
"'" => "\\'" ,
r"\" => "\\\\",
_ => ch,
});
Some(hint)
} else {
None
}
}
}
/// The core logic of `check_for_loop_iter` in `unnecessary_iter_cloned.rs`, this function wraps a
/// use of `CloneOrCopyVisitor`.
pub(super) fn clone_or_copy_needed<'tcx>(
cx: &LateContext<'tcx>,
pat: &Pat<'tcx>,
body: &'tcx Expr<'tcx>,
) -> (bool, Vec<&'tcx Expr<'tcx>>) {
let mut visitor = CloneOrCopyVisitor {
cx,
binding_hir_ids: pat_bindings(pat),
clone_or_copy_needed: false,
addr_of_exprs: Vec::new(),
};
visitor.visit_expr(body);
(visitor.clone_or_copy_needed, visitor.addr_of_exprs)
}
/// Returns a vector of all `HirId`s bound by the pattern.
fn pat_bindings(pat: &Pat<'_>) -> Vec<HirId> {
let mut collector = usage::ParamBindingIdCollector {
binding_hir_ids: Vec::new(),
};
collector.visit_pat(pat);
collector.binding_hir_ids
}
/// `clone_or_copy_needed` will be false when `CloneOrCopyVisitor` is done visiting if the only
/// operations performed on `binding_hir_ids` are:
/// * to take non-mutable references to them
/// * to use them as non-mutable `&self` in method calls
/// If any of `binding_hir_ids` is used in any other way, then `clone_or_copy_needed` will be true
/// when `CloneOrCopyVisitor` is done visiting.
struct CloneOrCopyVisitor<'cx, 'tcx> {
cx: &'cx LateContext<'tcx>,
binding_hir_ids: Vec<HirId>,
clone_or_copy_needed: bool,
addr_of_exprs: Vec<&'tcx Expr<'tcx>>,
}
impl<'cx, 'tcx> Visitor<'tcx> for CloneOrCopyVisitor<'cx, 'tcx> {
type NestedFilter = nested_filter::OnlyBodies;
fn nested_visit_map(&mut self) -> Self::Map {
self.cx.tcx.hir()
}
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
walk_expr(self, expr);
if self.is_binding(expr) {
if let Some(parent) = get_parent_expr(self.cx, expr) {
match parent.kind {
ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) => {
self.addr_of_exprs.push(parent);
return;
},
ExprKind::MethodCall(.., args, _) => {
if_chain! {
if args.iter().all(|arg| !self.is_binding(arg));
if let Some(method_def_id) = self.cx.typeck_results().type_dependent_def_id(parent.hir_id);
let method_ty = self.cx.tcx.type_of(method_def_id).subst_identity();
let self_ty = method_ty.fn_sig(self.cx.tcx).input(0).skip_binder();
if matches!(self_ty.kind(), ty::Ref(_, _, Mutability::Not));
then {
return;
}
}
},
_ => {},
}
}
self.clone_or_copy_needed = true;
}
}
}
impl<'cx, 'tcx> CloneOrCopyVisitor<'cx, 'tcx> {
fn is_binding(&self, expr: &Expr<'tcx>) -> bool {
self.binding_hir_ids
.iter()
.any(|hir_id| path_to_local_id(expr, *hir_id))
}
}
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