Auto merge of rust-lang#5868 - flip1995:rollup-5g8vft5, r=flip1995

Rollup of 5 pull requests

Successful merges:

 - rust-lang#5837 (needless_collect: catch x: Vec<_> = iter.collect(); x.into_iter() ...)
 - rust-lang#5846 (Handle mapping to Option in `map_flatten` lint)
 - rust-lang#5848 (Add derive_ord_xor_partial_ord lint)
 - rust-lang#5852 (Add lint for duplicate methods of trait bounds)
 - rust-lang#5856 (Remove old Symbol reexport)

Failed merges:

r? @ghost

changelog: rollup

Author: bors

CHANGELOG.md

@@ -1454,6 +1454,7 @@ Released 2018-09-13
 [`deprecated_semver`]: https://rust-lang.github.io/rust-clippy/master/index.html#deprecated_semver
 [`deref_addrof`]: https://rust-lang.github.io/rust-clippy/master/index.html#deref_addrof
 [`derive_hash_xor_eq`]: https://rust-lang.github.io/rust-clippy/master/index.html#derive_hash_xor_eq
+[`derive_ord_xor_partial_ord`]: https://rust-lang.github.io/rust-clippy/master/index.html#derive_ord_xor_partial_ord
 [`diverging_sub_expression`]: https://rust-lang.github.io/rust-clippy/master/index.html#diverging_sub_expression
 [`doc_markdown`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
 [`double_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#double_comparisons
@@ -1723,6 +1724,7 @@ Released 2018-09-13
 [`too_many_arguments`]: https://rust-lang.github.io/rust-clippy/master/index.html#too_many_arguments
 [`too_many_lines`]: https://rust-lang.github.io/rust-clippy/master/index.html#too_many_lines
 [`toplevel_ref_arg`]: https://rust-lang.github.io/rust-clippy/master/index.html#toplevel_ref_arg
+[`trait_duplication_in_bounds`]: https://rust-lang.github.io/rust-clippy/master/index.html#trait_duplication_in_bounds
 [`transmute_bytes_to_str`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_bytes_to_str
 [`transmute_float_to_int`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_float_to_int
 [`transmute_int_to_bool`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_int_to_bool

clippy_lints/src/attrs.rs

@@ -1,6 +1,5 @@
 //! checks for attributes
 
-use crate::reexport::Name;
 use crate::utils::{
     first_line_of_span, is_present_in_source, match_def_path, paths, snippet_opt, span_lint, span_lint_and_help,
     span_lint_and_sugg, span_lint_and_then, without_block_comments,
@@ -517,7 +516,7 @@ fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>
     }
 }
 
-fn check_attrs(cx: &LateContext<'_>, span: Span, name: Name, attrs: &[Attribute]) {
+fn check_attrs(cx: &LateContext<'_>, span: Span, name: Symbol, attrs: &[Attribute]) {
     if span.from_expansion() {
         return;
     }

clippy_lints/src/derive.rs

@@ -1,6 +1,7 @@
 use crate::utils::paths;
 use crate::utils::{
-    is_automatically_derived, is_copy, match_path, span_lint_and_help, span_lint_and_note, span_lint_and_then,
+    get_trait_def_id, is_automatically_derived, is_copy, match_path, span_lint_and_help, span_lint_and_note,
+    span_lint_and_then,
 };
 use if_chain::if_chain;
 use rustc_hir::def_id::DefId;
@@ -43,6 +44,57 @@ declare_clippy_lint! {
     "deriving `Hash` but implementing `PartialEq` explicitly"
 }
 
+declare_clippy_lint! {
+    /// **What it does:** Checks for deriving `Ord` but implementing `PartialOrd`
+    /// explicitly or vice versa.
+    ///
+    /// **Why is this bad?** The implementation of these traits must agree (for
+    /// example for use with `sort`) so it’s probably a bad idea to use a
+    /// default-generated `Ord` implementation with an explicitly defined
+    /// `PartialOrd`. In particular, the following must hold for any type
+    /// implementing `Ord`:
+    ///
+    /// ```text
+    /// k1.cmp(&k2) == k1.partial_cmp(&k2).unwrap()
+    /// ```
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    ///
+    /// ```rust,ignore
+    /// #[derive(Ord, PartialEq, Eq)]
+    /// struct Foo;
+    ///
+    /// impl PartialOrd for Foo {
+    ///     ...
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust,ignore
+    /// #[derive(PartialEq, Eq)]
+    /// struct Foo;
+    ///
+    /// impl PartialOrd for Foo {
+    ///     fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
+    ///        Some(self.cmp(other))
+    ///     }
+    /// }
+    ///
+    /// impl Ord for Foo {
+    ///     ...
+    /// }
+    /// ```
+    /// or, if you don't need a custom ordering:
+    /// ```rust,ignore
+    /// #[derive(Ord, PartialOrd, PartialEq, Eq)]
+    /// struct Foo;
+    /// ```
+    pub DERIVE_ORD_XOR_PARTIAL_ORD,
+    correctness,
+    "deriving `Ord` but implementing `PartialOrd` explicitly"
+}
+
 declare_clippy_lint! {
     /// **What it does:** Checks for explicit `Clone` implementations for `Copy`
     /// types.
@@ -103,7 +155,12 @@ declare_clippy_lint! {
     "deriving `serde::Deserialize` on a type that has methods using `unsafe`"
 }
 
-declare_lint_pass!(Derive => [EXPL_IMPL_CLONE_ON_COPY, DERIVE_HASH_XOR_EQ, UNSAFE_DERIVE_DESERIALIZE]);
+declare_lint_pass!(Derive => [
+    EXPL_IMPL_CLONE_ON_COPY,
+    DERIVE_HASH_XOR_EQ,
+    DERIVE_ORD_XOR_PARTIAL_ORD,
+    UNSAFE_DERIVE_DESERIALIZE
+]);
 
 impl<'tcx> LateLintPass<'tcx> for Derive {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
@@ -116,6 +173,7 @@ impl<'tcx> LateLintPass<'tcx> for Derive {
             let is_automatically_derived = is_automatically_derived(&*item.attrs);
 
             check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
+            check_ord_partial_ord(cx, item.span, trait_ref, ty, is_automatically_derived);
 
             if is_automatically_derived {
                 check_unsafe_derive_deserialize(cx, item, trait_ref, ty);
@@ -180,6 +238,60 @@ fn check_hash_peq<'tcx>(
     }
 }
 
+/// Implementation of the `DERIVE_ORD_XOR_PARTIAL_ORD` lint.
+fn check_ord_partial_ord<'tcx>(
+    cx: &LateContext<'tcx>,
+    span: Span,
+    trait_ref: &TraitRef<'_>,
+    ty: Ty<'tcx>,
+    ord_is_automatically_derived: bool,
+) {
+    if_chain! {
+        if let Some(ord_trait_def_id) = get_trait_def_id(cx, &paths::ORD);
+        if let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait();
+        if let Some(def_id) = &trait_ref.trait_def_id();
+        if *def_id == ord_trait_def_id;
+        then {
+            // Look for the PartialOrd implementations for `ty`
+            cx.tcx.for_each_relevant_impl(partial_ord_trait_def_id, ty, |impl_id| {
+                let partial_ord_is_automatically_derived = is_automatically_derived(&cx.tcx.get_attrs(impl_id));
+
+                if partial_ord_is_automatically_derived == ord_is_automatically_derived {
+                    return;
+                }
+
+                let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
+
+                // Only care about `impl PartialOrd<Foo> for Foo`
+                // For `impl PartialOrd<B> for A, input_types is [A, B]
+                if trait_ref.substs.type_at(1) == ty {
+                    let mess = if partial_ord_is_automatically_derived {
+                        "you are implementing `Ord` explicitly but have derived `PartialOrd`"
+                    } else {
+                        "you are deriving `Ord` but have implemented `PartialOrd` explicitly"
+                    };
+
+                    span_lint_and_then(
+                        cx,
+                        DERIVE_ORD_XOR_PARTIAL_ORD,
+                        span,
+                        mess,
+                        |diag| {
+                            if let Some(local_def_id) = impl_id.as_local() {
+                                let hir_id = cx.tcx.hir().as_local_hir_id(local_def_id);
+                                diag.span_note(
+                                    cx.tcx.hir().span(hir_id),
+                                    "`PartialOrd` implemented here"
+                                );
+                            }
+                        }
+                    );
+                }
+            });
+        }
+    }
+}
+
 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
 fn check_copy_clone<'tcx>(cx: &LateContext<'tcx>, item: &Item<'_>, trait_ref: &TraitRef<'_>, ty: Ty<'tcx>) {
     if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {

clippy_lints/src/lib.rs

@@ -322,10 +322,6 @@ mod zero_div_zero;
 
 pub use crate::utils::conf::Conf;
 
-mod reexport {
-    pub use rustc_span::Symbol as Name;
-}
-
 /// Register all pre expansion lints
 ///
 /// Pre-expansion lints run before any macro expansion has happened.
@@ -513,6 +509,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &default_trait_access::DEFAULT_TRAIT_ACCESS,
         &dereference::EXPLICIT_DEREF_METHODS,
         &derive::DERIVE_HASH_XOR_EQ,
+        &derive::DERIVE_ORD_XOR_PARTIAL_ORD,
         &derive::EXPL_IMPL_CLONE_ON_COPY,
         &derive::UNSAFE_DERIVE_DESERIALIZE,
         &doc::DOC_MARKDOWN,
@@ -786,6 +783,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &tabs_in_doc_comments::TABS_IN_DOC_COMMENTS,
         &temporary_assignment::TEMPORARY_ASSIGNMENT,
         &to_digit_is_some::TO_DIGIT_IS_SOME,
+        &trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS,
         &trait_bounds::TYPE_REPETITION_IN_BOUNDS,
         &transmute::CROSSPOINTER_TRANSMUTE,
         &transmute::TRANSMUTE_BYTES_TO_STR,
@@ -1174,6 +1172,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&ranges::RANGE_PLUS_ONE),
         LintId::of(&shadow::SHADOW_UNRELATED),
         LintId::of(&strings::STRING_ADD_ASSIGN),
+        LintId::of(&trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS),
         LintId::of(&trait_bounds::TYPE_REPETITION_IN_BOUNDS),
         LintId::of(&trivially_copy_pass_by_ref::TRIVIALLY_COPY_PASS_BY_REF),
         LintId::of(&types::CAST_LOSSLESS),
@@ -1230,6 +1229,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&copies::IFS_SAME_COND),
         LintId::of(&copies::IF_SAME_THEN_ELSE),
         LintId::of(&derive::DERIVE_HASH_XOR_EQ),
+        LintId::of(&derive::DERIVE_ORD_XOR_PARTIAL_ORD),
         LintId::of(&doc::MISSING_SAFETY_DOC),
         LintId::of(&doc::NEEDLESS_DOCTEST_MAIN),
         LintId::of(&double_comparison::DOUBLE_COMPARISONS),
@@ -1648,6 +1648,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&copies::IFS_SAME_COND),
         LintId::of(&copies::IF_SAME_THEN_ELSE),
         LintId::of(&derive::DERIVE_HASH_XOR_EQ),
+        LintId::of(&derive::DERIVE_ORD_XOR_PARTIAL_ORD),
         LintId::of(&drop_bounds::DROP_BOUNDS),
         LintId::of(&drop_forget_ref::DROP_COPY),
         LintId::of(&drop_forget_ref::DROP_REF),

clippy_lints/src/lifetimes.rs

@@ -13,9 +13,8 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::map::Map;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::Span;
-use rustc_span::symbol::kw;
+use rustc_span::symbol::{kw, Symbol};
 
-use crate::reexport::Name;
 use crate::utils::{in_macro, last_path_segment, span_lint, trait_ref_of_method};
 
 declare_clippy_lint! {
@@ -113,7 +112,7 @@ impl<'tcx> LateLintPass<'tcx> for Lifetimes {
 enum RefLt {
     Unnamed,
     Static,
-    Named(Name),
+    Named(Symbol),
 }
 
 fn check_fn_inner<'tcx>(
@@ -456,7 +455,7 @@ fn has_where_lifetimes<'tcx>(cx: &LateContext<'tcx>, where_clause: &'tcx WhereCl
 }
 
 struct LifetimeChecker {
-    map: FxHashMap<Name, Span>,
+    map: FxHashMap<Symbol, Span>,
 }
 
 impl<'tcx> Visitor<'tcx> for LifetimeChecker {