Auto merge of rust-lang#9199 - Xiretza:unused-self-exported-api, r=Ja…

…rcho

unused_self: respect avoid-breaking-exported-api

```
changelog: [`unused_self`]: Now respects the `avoid-breaking-exported-api` config option
```

Fixes rust-lang#9195.

I mostly copied the implementation from `unnecessary_wraps`, since I don't have much understanding of rustc internals.

clippy_lints/src/lib.rs

@@ -782,7 +782,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         ))
     });
     store.register_late_pass(|| Box::new(default::Default::default()));
-    store.register_late_pass(|| Box::new(unused_self::UnusedSelf));
+    store.register_late_pass(move || Box::new(unused_self::UnusedSelf::new(avoid_breaking_exported_api)));
     store.register_late_pass(|| Box::new(mutable_debug_assertion::DebugAssertWithMutCall));
     store.register_late_pass(|| Box::new(exit::Exit));
     store.register_late_pass(|| Box::new(to_digit_is_some::ToDigitIsSome));

clippy_lints/src/unused_self.rs

@@ -3,7 +3,7 @@ use clippy_utils::visitors::is_local_used;
 use if_chain::if_chain;
 use rustc_hir::{Impl, ImplItem, ImplItemKind, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -35,7 +35,19 @@ declare_clippy_lint! {
     "methods that contain a `self` argument but don't use it"
 }
 
-declare_lint_pass!(UnusedSelf => [UNUSED_SELF]);
+pub struct UnusedSelf {
+    avoid_breaking_exported_api: bool,
+}
+
+impl_lint_pass!(UnusedSelf => [UNUSED_SELF]);
+
+impl UnusedSelf {
+    pub fn new(avoid_breaking_exported_api: bool) -> Self {
+        Self {
+            avoid_breaking_exported_api,
+        }
+    }
+}
 
 impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &ImplItem<'_>) {
@@ -49,6 +61,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
             if let ItemKind::Impl(Impl { of_trait: None, .. }) = parent_item.kind;
             if assoc_item.fn_has_self_parameter;
             if let ImplItemKind::Fn(.., body_id) = &impl_item.kind;
+            if !cx.access_levels.is_exported(impl_item.def_id) || !self.avoid_breaking_exported_api;
             let body = cx.tcx.hir().body(*body_id);
             if let [self_param, ..] = body.params;
             if !is_local_used(cx, body, self_param.pat.hir_id);

clippy_lints/src/utils/conf.rs

@@ -191,7 +191,7 @@ macro_rules! define_Conf {
 }
 
 define_Conf! {
-    /// Lint: ENUM_VARIANT_NAMES, LARGE_TYPES_PASSED_BY_VALUE, TRIVIALLY_COPY_PASS_BY_REF, UNNECESSARY_WRAPS, UPPER_CASE_ACRONYMS, WRONG_SELF_CONVENTION, BOX_COLLECTION, REDUNDANT_ALLOCATION, RC_BUFFER, VEC_BOX, OPTION_OPTION, LINKEDLIST, RC_MUTEX.
+    /// Lint: ENUM_VARIANT_NAMES, LARGE_TYPES_PASSED_BY_VALUE, TRIVIALLY_COPY_PASS_BY_REF, UNNECESSARY_WRAPS, UNUSED_SELF, UPPER_CASE_ACRONYMS, WRONG_SELF_CONVENTION, BOX_COLLECTION, REDUNDANT_ALLOCATION, RC_BUFFER, VEC_BOX, OPTION_OPTION, LINKEDLIST, RC_MUTEX.
     ///
     /// Suppress lints whenever the suggested change would cause breakage for other crates.
     (avoid_breaking_exported_api: bool = true),

tests/ui/unused_self.rs

@@ -53,8 +53,17 @@ mod unused_self_allow {
         // shouldn't trigger
         fn unused_self_move(self) {}
     }
+
+    pub struct D;
+
+    impl D {
+        // shouldn't trigger for public methods
+        pub fn unused_self_move(self) {}
+    }
 }
 
+pub use unused_self_allow::D;
+
 mod used_self {
     use std::pin::Pin;