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use rustc_front::hir::*;
use rustc::lint::*;
use rustc::middle::ty;
use rustc::middle::subst::Subst;
use std::iter;
use std::borrow::Cow;
use utils::{snippet, span_lint, match_path, match_type, walk_ptrs_ty_depth};
use utils::{OPTION_PATH, RESULT_PATH, STRING_PATH};
use self::SelfKind::*;
use self::OutType::*;
#[derive(Copy,Clone)]
pub struct MethodsPass;
declare_lint!(pub OPTION_UNWRAP_USED, Allow,
"using `Option.unwrap()`, which should at least get a better message using `expect()`");
declare_lint!(pub RESULT_UNWRAP_USED, Allow,
"using `Result.unwrap()`, which might be better handled");
declare_lint!(pub STR_TO_STRING, Warn,
"using `to_string()` on a str, which should be `to_owned()`");
declare_lint!(pub STRING_TO_STRING, Warn,
"calling `String.to_string()` which is a no-op");
declare_lint!(pub SHOULD_IMPLEMENT_TRAIT, Warn,
"defining a method that should be implementing a std trait");
declare_lint!(pub WRONG_SELF_CONVENTION, Warn,
"defining a method named with an established prefix (like \"into_\") that takes \
`self` with the wrong convention");
declare_lint!(pub WRONG_PUB_SELF_CONVENTION, Allow,
"defining a public method named with an established prefix (like \"into_\") that takes \
`self` with the wrong convention");
impl LintPass for MethodsPass {
fn get_lints(&self) -> LintArray {
lint_array!(OPTION_UNWRAP_USED, RESULT_UNWRAP_USED, STR_TO_STRING, STRING_TO_STRING,
SHOULD_IMPLEMENT_TRAIT, WRONG_SELF_CONVENTION)
}
}
impl LateLintPass for MethodsPass {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let ExprMethodCall(ref name, _, ref args) = expr.node {
let (obj_ty, ptr_depth) = walk_ptrs_ty_depth(cx.tcx.expr_ty(&args[0]));
if name.node.as_str() == "unwrap" {
if match_type(cx, obj_ty, &OPTION_PATH) {
span_lint(cx, OPTION_UNWRAP_USED, expr.span,
"used unwrap() on an Option value. If you don't want \
to handle the None case gracefully, consider using \
expect() to provide a better panic message");
} else if match_type(cx, obj_ty, &RESULT_PATH) {
span_lint(cx, RESULT_UNWRAP_USED, expr.span,
"used unwrap() on a Result value. Graceful handling \
of Err values is preferred");
}
}
else if name.node.as_str() == "to_string" {
if obj_ty.sty == ty::TyStr {
let mut arg_str = snippet(cx, args[0].span, "_");
if ptr_depth > 1 {
arg_str = Cow::Owned(format!(
"({}{})",
iter::repeat('*').take(ptr_depth - 1).collect::<String>(),
arg_str));
}
span_lint(cx, STR_TO_STRING, expr.span, &format!(
"`{}.to_owned()` is faster", arg_str));
} else if match_type(cx, obj_ty, &STRING_PATH) {
span_lint(cx, STRING_TO_STRING, expr.span, "`String.to_string()` is a no-op; use \
`clone()` to make a copy");
}
}
}
}
fn check_item(&mut self, cx: &LateContext, item: &Item) {
if let ItemImpl(_, _, _, None, ref ty, ref items) = item.node {
for implitem in items {
let name = implitem.name;
if let MethodImplItem(ref sig, _) = implitem.node {
for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
if_let_chain! {
[
name.as_str() == method_name,
sig.decl.inputs.len() == n_args,
out_type.matches(&sig.decl.output),
self_kind.matches(&sig.explicit_self.node, false)
], {
span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!(
"defining a method called `{}` on this type; consider implementing \
the `{}` trait or choosing a less ambiguous name", name, trait_name));
}
}
}
let is_copy = is_copy(cx, &ty, &item);
for &(prefix, self_kinds) in &CONVENTIONS {
if name.as_str().starts_with(prefix) &&
!self_kinds.iter().any(|k| k.matches(&sig.explicit_self.node, is_copy)) {
let lint = if item.vis == Visibility::Public {
WRONG_PUB_SELF_CONVENTION
} else {
WRONG_SELF_CONVENTION
};
span_lint(cx, lint, sig.explicit_self.span, &format!(
"methods called `{}*` usually take {}; consider choosing a less \
ambiguous name", prefix,
&self_kinds.iter().map(|k| k.description()).collect::<Vec<_>>().join(" or ")));
}
}
}
}
}
}
}
const CONVENTIONS: [(&'static str, &'static [SelfKind]); 5] = [
("into_", &[ValueSelf]),
("to_", &[RefSelf]),
("as_", &[RefSelf, RefMutSelf]),
("is_", &[RefSelf, NoSelf]),
("from_", &[NoSelf]),
];
const TRAIT_METHODS: [(&'static str, usize, SelfKind, OutType, &'static str); 30] = [
("add", 2, ValueSelf, AnyType, "std::ops::Add"),
("sub", 2, ValueSelf, AnyType, "std::ops::Sub"),
("mul", 2, ValueSelf, AnyType, "std::ops::Mul"),
("div", 2, ValueSelf, AnyType, "std::ops::Div"),
("rem", 2, ValueSelf, AnyType, "std::ops::Rem"),
("shl", 2, ValueSelf, AnyType, "std::ops::Shl"),
("shr", 2, ValueSelf, AnyType, "std::ops::Shr"),
("bitand", 2, ValueSelf, AnyType, "std::ops::BitAnd"),
("bitor", 2, ValueSelf, AnyType, "std::ops::BitOr"),
("bitxor", 2, ValueSelf, AnyType, "std::ops::BitXor"),
("neg", 1, ValueSelf, AnyType, "std::ops::Neg"),
("not", 1, ValueSelf, AnyType, "std::ops::Not"),
("drop", 1, RefMutSelf, UnitType, "std::ops::Drop"),
("index", 2, RefSelf, RefType, "std::ops::Index"),
("index_mut", 2, RefMutSelf, RefType, "std::ops::IndexMut"),
("deref", 1, RefSelf, RefType, "std::ops::Deref"),
("deref_mut", 1, RefMutSelf, RefType, "std::ops::DerefMut"),
("clone", 1, RefSelf, AnyType, "std::clone::Clone"),
("borrow", 1, RefSelf, RefType, "std::borrow::Borrow"),
("borrow_mut", 1, RefMutSelf, RefType, "std::borrow::BorrowMut"),
("as_ref", 1, RefSelf, RefType, "std::convert::AsRef"),
("as_mut", 1, RefMutSelf, RefType, "std::convert::AsMut"),
("eq", 2, RefSelf, BoolType, "std::cmp::PartialEq"),
("cmp", 2, RefSelf, AnyType, "std::cmp::Ord"),
("default", 0, NoSelf, AnyType, "std::default::Default"),
("hash", 2, RefSelf, UnitType, "std::hash::Hash"),
("next", 1, RefMutSelf, AnyType, "std::iter::Iterator"),
("into_iter", 1, ValueSelf, AnyType, "std::iter::IntoIterator"),
("from_iter", 1, NoSelf, AnyType, "std::iter::FromIterator"),
("from_str", 1, NoSelf, AnyType, "std::str::FromStr"),
];
#[derive(Clone, Copy)]
enum SelfKind {
ValueSelf,
RefSelf,
RefMutSelf,
NoSelf,
}
impl SelfKind {
fn matches(&self, slf: &ExplicitSelf_, allow_value_for_ref: bool) -> bool {
match (self, slf) {
(&ValueSelf, &SelfValue(_)) => true,
(&RefSelf, &SelfRegion(_, Mutability::MutImmutable, _)) => true,
(&RefMutSelf, &SelfRegion(_, Mutability::MutMutable, _)) => true,
(&RefSelf, &SelfValue(_)) => allow_value_for_ref,
(&RefMutSelf, &SelfValue(_)) => allow_value_for_ref,
(&NoSelf, &SelfStatic) => true,
(_, &SelfExplicit(ref ty, _)) => self.matches_explicit_type(ty, allow_value_for_ref),
_ => false
}
}
fn matches_explicit_type(&self, ty: &Ty, allow_value_for_ref: bool) -> bool {
match (self, &ty.node) {
(&ValueSelf, &TyPath(..)) => true,
(&RefSelf, &TyRptr(_, MutTy { mutbl: Mutability::MutImmutable, .. })) => true,
(&RefMutSelf, &TyRptr(_, MutTy { mutbl: Mutability::MutMutable, .. })) => true,
(&RefSelf, &TyPath(..)) => allow_value_for_ref,
(&RefMutSelf, &TyPath(..)) => allow_value_for_ref,
_ => false
}
}
fn description(&self) -> &'static str {
match *self {
ValueSelf => "self by value",
RefSelf => "self by reference",
RefMutSelf => "self by mutable reference",
NoSelf => "no self",
}
}
}
#[derive(Clone, Copy)]
enum OutType {
UnitType,
BoolType,
AnyType,
RefType,
}
impl OutType {
fn matches(&self, ty: &FunctionRetTy) -> bool {
match (self, ty) {
(&UnitType, &DefaultReturn(_)) => true,
(&UnitType, &Return(ref ty)) if ty.node == TyTup(vec![]) => true,
(&BoolType, &Return(ref ty)) if is_bool(ty) => true,
(&AnyType, &Return(ref ty)) if ty.node != TyTup(vec![]) => true,
(&RefType, &Return(ref ty)) => {
if let TyRptr(_, _) = ty.node { true } else { false }
}
_ => false
}
}
}
fn is_bool(ty: &Ty) -> bool {
if let TyPath(None, ref p) = ty.node {
if match_path(p, &["bool"]) {
return true;
}
}
false
}
fn is_copy(cx: &LateContext, ast_ty: &Ty, item: &Item) -> bool {
match cx.tcx.ast_ty_to_ty_cache.borrow().get(&ast_ty.id) {
None => false,
Some(ty) => {
let env = ty::ParameterEnvironment::for_item(cx.tcx, item.id);
!ty.subst(cx.tcx, &env.free_substs).moves_by_default(&env, ast_ty.span)
}
}
}