Add clippy::result_as_ref_deref lint

CHANGELOG.md

@@ -5881,6 +5881,7 @@ Released 2018-09-13
 [`replace_consts`]: https://rust-lang.github.io/rust-clippy/master/index.html#replace_consts
 [`reserve_after_initialization`]: https://rust-lang.github.io/rust-clippy/master/index.html#reserve_after_initialization
 [`rest_pat_in_fully_bound_structs`]: https://rust-lang.github.io/rust-clippy/master/index.html#rest_pat_in_fully_bound_structs
+[`result_as_ref_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_as_ref_deref
 [`result_expect_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_expect_used
 [`result_filter_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_filter_map
 [`result_large_err`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err

clippy_config/src/msrvs.rs

@@ -20,7 +20,7 @@ msrv_aliases! {
  1,83,0 { CONST_EXTERN_FN }
  1,83,0 { CONST_FLOAT_BITS_CONV }
  1,81,0 { LINT_REASONS_STABILIZATION }
- 1,80,0 { BOX_INTO_ITER}
+ 1,80,0 { BOX_INTO_ITER }
  1,77,0 { C_STR_LITERALS }
  1,76,0 { PTR_FROM_REF, OPTION_RESULT_INSPECT }
  1,73,0 { MANUAL_DIV_CEIL }
@@ -39,7 +39,7 @@ msrv_aliases! {
  1,52,0 { STR_SPLIT_ONCE, REM_EUCLID_CONST }
  1,51,0 { BORROW_AS_PTR, SEEK_FROM_CURRENT, UNSIGNED_ABS }
  1,50,0 { BOOL_THEN, CLAMP }
- 1,47,0 { TAU, IS_ASCII_DIGIT_CONST, ARRAY_IMPL_ANY_LEN, SATURATING_SUB_CONST }
+ 1,47,0 { TAU, IS_ASCII_DIGIT_CONST, ARRAY_IMPL_ANY_LEN, SATURATING_SUB_CONST, RESULT_AS_DEREF }
  1,46,0 { CONST_IF_MATCH }
  1,45,0 { STR_STRIP_PREFIX }
  1,43,0 { LOG2_10, LOG10_2, NUMERIC_ASSOCIATED_CONSTANTS }

clippy_lints/src/declared_lints.rs

@@ -445,6 +445,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
  crate::methods::READ_LINE_WITHOUT_TRIM_INFO,
  crate::methods::REDUNDANT_AS_STR_INFO,
  crate::methods::REPEAT_ONCE_INFO,
+ crate::methods::RESULT_AS_REF_DEREF_INFO,
  crate::methods::RESULT_FILTER_MAP_INFO,
  crate::methods::RESULT_MAP_OR_INTO_OPTION_INFO,
  crate::methods::SEARCH_IS_SOME_INFO,

clippy_lints/src/methods/option_as_ref_deref.rs → clippy_lints/src/methods/manual_as_ref_deref.rs

@@ -9,9 +9,16 @@ use rustc_lint::LateContext;
 use rustc_middle::ty;
 use rustc_span::{Symbol, sym};
 
-use super::OPTION_AS_REF_DEREF;
+use super::{OPTION_AS_REF_DEREF, RESULT_AS_REF_DEREF};
 
-/// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Target {
+ Option,
+ Result,
+}
+
+/// lint use of `_.as_ref().map(Deref::deref)` for `Option`s and `Result`s
+#[allow(clippy::too_many_lines)]
 pub(super) fn check(
  cx: &LateContext<'_>,
  expr: &hir::Expr<'_>,
@@ -20,14 +27,23 @@ pub(super) fn check(
  is_mut: bool,
  msrv: &Msrv,
 ) {
- if !msrv.meets(msrvs::OPTION_AS_DEREF) {
- return;
- }
-
  let same_mutability = |m| (is_mut && m == &hir::Mutability::Mut) || (!is_mut && m == &hir::Mutability::Not);
 
- let option_ty = cx.typeck_results().expr_ty(as_ref_recv);
- if !is_type_diagnostic_item(cx, option_ty, sym::Option) {
+ let target = 'target: {
+ let target_ty = cx.typeck_results().expr_ty(as_ref_recv);
+ if is_type_diagnostic_item(cx, target_ty, sym::Option) {
+ break 'target Target::Option;
+ }
+ if is_type_diagnostic_item(cx, target_ty, sym::Result) {
+ break 'target Target::Result;
+ }
+ return;
+ };
+
+ if target == Target::Option && !msrv.meets(msrvs::OPTION_AS_DEREF) {
+ return;
+ }
+ if target == Target::Result && !msrv.meets(msrvs::RESULT_AS_DEREF) {
  return;
  }
 
@@ -103,10 +119,20 @@ pub(super) fn check(
  let hint = format!("{}.{method_hint}()", snippet(cx, as_ref_recv.span, ".."));
  let suggestion = format!("consider using {method_hint}");
 
- let msg = format!("called `{current_method}` on an `Option` value");
+ let target_name_with_article = match target {
+ Target::Option => "an `Option`",
+ Target::Result => "a `Result`",
+ };
+ let msg = format!("called `{current_method}` on {target_name_with_article} value");
+
+ let lint = match target {
+ Target::Option => OPTION_AS_REF_DEREF,
+ Target::Result => RESULT_AS_REF_DEREF,
+ };
+
  span_lint_and_sugg(
  cx,
- OPTION_AS_REF_DEREF,
+ lint,
  expr.span,
  msg,
  suggestion,

clippy_lints/src/methods/mod.rs

@@ -52,6 +52,7 @@ mod iter_skip_zero;
 mod iter_with_drain;
 mod iterator_step_by_zero;
 mod join_absolute_paths;
+mod manual_as_ref_deref;
 mod manual_c_str_literals;
 mod manual_inspect;
 mod manual_is_variant_and;
@@ -76,7 +77,6 @@ mod obfuscated_if_else;
 mod ok_expect;
 mod open_options;
 mod option_as_ref_cloned;
-mod option_as_ref_deref;
 mod option_map_or_err_ok;
 mod option_map_or_none;
 mod option_map_unwrap_or;
@@ -1759,7 +1759,8 @@ declare_clippy_lint! {
 
 declare_clippy_lint! {
  /// ### What it does
- /// Checks for usage of `_.as_ref().map(Deref::deref)` or its aliases (such as String::as_str).
+ /// Checks for usage of `_.as_ref().map(Deref::deref)` or its aliases
+ /// (such as `String::as_str`) on `Option`.
  ///
  /// ### Why is this bad?
  /// Readability, this can be written more concisely as
@@ -1783,6 +1784,33 @@ declare_clippy_lint! {
  "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
 }
 
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for usage of `_.as_ref().map(Deref::deref)` or its aliases
+ /// (such as `String::as_str`) on `Result`.
+ ///
+ /// ### Why is this bad?
+ /// Readability, this can be written more concisely as
+ /// `_.as_deref()`.
+ ///
+ /// ### Example
+ /// ```no_run
+ /// # let res = Ok::<_, ()>("".to_string());
+ /// res.as_ref().map(String::as_str)
+ /// # ;
+ /// ```
+ /// Use instead:
+ /// ```no_run
+ /// # let res = OK::<_, ()>("".to_string());
+ /// res.as_deref()
+ /// # ;
+ /// ```
+ #[clippy::version = "1.83.0"]
+ pub RESULT_AS_REF_DEREF,
+ complexity,
+ "using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
+}
+
 declare_clippy_lint! {
  /// ### What it does
  /// Checks for usage of `iter().next()` on a Slice or an Array
@@ -4252,6 +4280,7 @@ impl_lint_pass!(Methods => [
  ZST_OFFSET,
  FILETYPE_IS_FILE,
  OPTION_AS_REF_DEREF,
+ RESULT_AS_REF_DEREF,
  UNNECESSARY_LAZY_EVALUATIONS,
  MAP_COLLECT_RESULT_UNIT,
  FROM_ITER_INSTEAD_OF_COLLECT,
@@ -4821,8 +4850,8 @@ impl Methods {
  }
  if let Some((name, recv2, args, span2, _)) = method_call(recv) {
  match (name, args) {
- ("as_mut", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, true, &self.msrv),
- ("as_ref", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, false, &self.msrv),
+ ("as_mut", []) => manual_as_ref_deref::check(cx, expr, recv2, m_arg, true, &self.msrv),
+ ("as_ref", []) => manual_as_ref_deref::check(cx, expr, recv2, m_arg, false, &self.msrv),
  ("filter", [f_arg]) => {
  filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, false);
  },

tests/ui/result_as_ref_deref.fixed

@@ -0,0 +1,53 @@
+#![allow(unused, clippy::redundant_clone, clippy::useless_vec)]
+#![warn(clippy::result_as_ref_deref)]
+
+use std::ffi::{CString, OsString};
+use std::ops::{Deref, DerefMut};
+use std::path::PathBuf;
+
+fn main() {
+ let mut res = Ok::<_, ()>(String::from("123"));
+
+ let _ = res.clone().as_deref().map(str::len);
+
+ #[rustfmt::skip]
+ let _ = res.clone().as_deref()
+ .map(str::len);
+
+ let _ = res.as_deref_mut();
+
+ let _ = res.as_deref();
+ let _ = res.as_deref();
+ let _ = res.as_deref_mut();
+ let _ = res.as_deref_mut();
+ let _ = Ok::<_, ()>(CString::new(vec![]).unwrap()).as_deref();
+ let _ = Ok::<_, ()>(OsString::new()).as_deref();
+ let _ = Ok::<_, ()>(PathBuf::new()).as_deref();
+ let _ = Ok::<_, ()>(Vec::<()>::new()).as_deref();
+ let _ = Ok::<_, ()>(Vec::<()>::new()).as_deref_mut();
+
+ let _ = res.as_deref();
+ let _ = res.clone().as_deref_mut().map(|x| x.len());
+
+ let vc = vec![String::new()];
+ let _ = Ok::<_, ()>(1_usize).as_ref().map(|x| vc[*x].as_str()); // should not be linted
+
+ let _: Result<&str, &()> = Ok(&String::new()).as_ref().map(|x| x.as_str()); // should not be linted
+
+ let _ = res.as_deref();
+ let _ = res.as_deref_mut();
+
+ let _ = res.as_deref();
+}
+
+#[clippy::msrv = "1.46"]
+fn msrv_1_46() {
+ let res = Ok::<_, ()>(String::from("123"));
+ let _ = res.as_ref().map(String::as_str);
+}
+
+#[clippy::msrv = "1.47"]
+fn msrv_1_47() {
+ let res = Ok::<_, ()>(String::from("123"));
+ let _ = res.as_deref();
+}

tests/ui/result_as_ref_deref.rs

@@ -0,0 +1,58 @@
+#![allow(unused, clippy::redundant_clone, clippy::useless_vec)]
+#![warn(clippy::result_as_ref_deref)]
+
+use std::ffi::{CString, OsString};
+use std::ops::{Deref, DerefMut};
+use std::path::PathBuf;
+
+fn main() {
+ let mut res = Ok::<_, ()>(String::from("123"));
+
+ let _ = res.clone().as_ref().map(Deref::deref).map(str::len);
+
+ #[rustfmt::skip]
+ let _ = res.clone()
+ .as_ref().map(
+ Deref::deref
+ )
+ .map(str::len);
+
+ let _ = res.as_mut().map(DerefMut::deref_mut);
+
+ let _ = res.as_ref().map(String::as_str);
+ let _ = res.as_ref().map(|x| x.as_str());
+ let _ = res.as_mut().map(String::as_mut_str);
+ let _ = res.as_mut().map(|x| x.as_mut_str());
+ let _ = Ok::<_, ()>(CString::new(vec![]).unwrap())
+ .as_ref()
+ .map(CString::as_c_str);
+ let _ = Ok::<_, ()>(OsString::new()).as_ref().map(OsString::as_os_str);
+ let _ = Ok::<_, ()>(PathBuf::new()).as_ref().map(PathBuf::as_path);
+ let _ = Ok::<_, ()>(Vec::<()>::new()).as_ref().map(Vec::as_slice);
+ let _ = Ok::<_, ()>(Vec::<()>::new()).as_mut().map(Vec::as_mut_slice);
+
+ let _ = res.as_ref().map(|x| x.deref());
+ let _ = res.clone().as_mut().map(|x| x.deref_mut()).map(|x| x.len());
+
+ let vc = vec![String::new()];
+ let _ = Ok::<_, ()>(1_usize).as_ref().map(|x| vc[*x].as_str()); // should not be linted
+
+ let _: Result<&str, &()> = Ok(&String::new()).as_ref().map(|x| x.as_str()); // should not be linted
+
+ let _ = res.as_ref().map(|x| &**x);
+ let _ = res.as_mut().map(|x| &mut **x);
+
+ let _ = res.as_ref().map(std::ops::Deref::deref);
+}
+
+#[clippy::msrv = "1.46"]
+fn msrv_1_46() {
+ let res = Ok::<_, ()>(String::from("123"));
+ let _ = res.as_ref().map(String::as_str);
+}
+
+#[clippy::msrv = "1.47"]
+fn msrv_1_47() {
+ let res = Ok::<_, ()>(String::from("123"));
+ let _ = res.as_ref().map(String::as_str);
+}