Add ControlFlow.{map_break,map_continue} to useless_conversion

Author: samueltardieu

clippy_lints/src/methods/mod.rs

@@ -4984,6 +4984,9 @@ impl Methods {
                     manual_inspect::check(cx, expr, m_arg, name, span, &self.msrv);
                     crate::useless_conversion::check_function_application(cx, expr, recv, m_arg);
                 },
+                ("map_break" | "map_continue", [m_arg]) => {
+                    crate::useless_conversion::check_function_application(cx, expr, recv, m_arg);
+                },
                 ("map_or", [def, map]) => {
                     option_map_or_none::check(cx, expr, recv, def, map);
                     manual_ok_or::check(cx, expr, recv, def, map);

clippy_lints/src/useless_conversion.rs

@@ -2,7 +2,9 @@ use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg, span_lin
 use clippy_utils::source::{snippet, snippet_with_applicability, snippet_with_context};
 use clippy_utils::sugg::{DiagExt as _, Sugg};
 use clippy_utils::ty::{is_copy, is_type_diagnostic_item, same_type_and_consts};
-use clippy_utils::{get_parent_expr, is_trait_item, is_trait_method, is_ty_alias, path_to_local};
+use clippy_utils::{
+    get_parent_expr, is_inherent_method_call, is_trait_item, is_trait_method, is_ty_alias, path_to_local,
+};
 use rustc_errors::Applicability;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{BindingMode, Expr, ExprKind, HirId, MatchSource, Node, PatKind};
@@ -12,7 +14,7 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::{self, AdtDef, EarlyBinder, GenericArg, GenericArgsRef, Ty, TypeVisitableExt};
 use rustc_session::impl_lint_pass;
-use rustc_span::{Span, sym};
+use rustc_span::{Span, Symbol, sym};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 
 declare_clippy_lint! {
@@ -386,11 +388,8 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
 /// Check if `arg` is a `Into::into` or `From::from` applied to `receiver` to give `expr`, through a
 /// higher-order mapping function.
 pub fn check_function_application(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg: &Expr<'_>) {
-    let recv_ty = cx.typeck_results().expr_ty(recv);
-    let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
-    if let Some(recv_ty_defid) = recv_ty.ty_adt_def().map(AdtDef::did)
-        && let Some(diag_name) = cx.tcx.get_diagnostic_name(recv_ty_defid)
-        && matches!(diag_name, sym::Option | sym::Result)
+    if has_eligible_receiver(cx, recv, expr)
+        && let expr_ty = cx.typeck_results().expr_ty_adjusted(expr)
         && same_type_and_consts(expr_ty, cx.typeck_results().expr_ty_adjusted(recv))
         && (is_trait_item(cx, arg, sym::Into) || is_trait_item(cx, arg, sym::From))
     {
@@ -410,3 +409,29 @@ pub fn check_function_application(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &
         );
     }
 }
+
+fn has_eligible_receiver(cx: &LateContext<'_>, recv: &Expr<'_>, expr: &Expr<'_>) -> bool {
+    let recv_ty = cx.typeck_results().expr_ty(recv);
+    if is_inherent_method_call(cx, expr)
+        && let Some(recv_ty_defid) = recv_ty.ty_adt_def().map(AdtDef::did)
+    {
+        if let Some(diag_name) = cx.tcx.get_diagnostic_name(recv_ty_defid)
+            && matches!(diag_name, sym::Option | sym::Result)
+        {
+            return true;
+        }
+
+        // Necessary for `core::ops::control_flow::ControlFlow` until a diagnostic item
+        // has been added.
+        let def_path = cx.get_def_path(recv_ty_defid);
+        if def_path
+            .iter()
+            .map(Symbol::as_str)
+            .zip(["core", "ops", "control_flow", "ControlFlow"])
+            .all(|(sym, s)| sym == s)
+        {
+            return true;
+        }
+    }
+    false
+}

tests/ui/useless_conversion.fixed

@@ -3,6 +3,8 @@
 // FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
 #![allow(static_mut_refs)]
 
+use std::ops::ControlFlow;
+
 fn test_generic<T: Copy>(val: T) -> T {
     let _ = val;
     val
@@ -308,6 +310,13 @@ fn direct_application() {
     let _: Result<(), std::io::Error> = test_issue_3913();
     //~^ useless_conversion
 
+    let c: ControlFlow<()> = ControlFlow::Continue(());
+    let _: ControlFlow<()> = c;
+    //~^ useless_conversion
+    let c: ControlFlow<()> = ControlFlow::Continue(());
+    let _: ControlFlow<()> = c;
+    //~^ useless_conversion
+
     struct Absorb;
     impl From<()> for Absorb {
         fn from(_: ()) -> Self {

tests/ui/useless_conversion.rs

@@ -3,6 +3,8 @@
 // FIXME(static_mut_refs): Do not allow `static_mut_refs` lint
 #![allow(static_mut_refs)]
 
+use std::ops::ControlFlow;
+
 fn test_generic<T: Copy>(val: T) -> T {
     let _ = T::from(val);
     val.into()
@@ -308,6 +310,13 @@ fn direct_application() {
     let _: Result<(), std::io::Error> = test_issue_3913().map_err(From::from);
     //~^ useless_conversion
 
+    let c: ControlFlow<()> = ControlFlow::Continue(());
+    let _: ControlFlow<()> = c.map_break(Into::into);
+    //~^ useless_conversion
+    let c: ControlFlow<()> = ControlFlow::Continue(());
+    let _: ControlFlow<()> = c.map_continue(Into::into);
+    //~^ useless_conversion
+
     struct Absorb;
     impl From<()> for Absorb {
         fn from(_: ()) -> Self {