fix: map_unwrap_or fail to cover Result::unwrap_or

Author: profetia

clippy_lints/src/methods/map_unwrap_or.rs

@@ -1,77 +1,193 @@
-use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
+use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::msrvs::{self, Msrv};
-use clippy_utils::source::snippet;
-use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::usage::mutated_variables;
+use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::ty::{is_copy, is_type_diagnostic_item};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Applicability;
-use rustc_hir as hir;
+use rustc_hir::def::Res;
+use rustc_hir::intravisit::{Visitor, walk_path};
+use rustc_hir::{ExprKind, HirId, Node, PatKind, Path, QPath};
 use rustc_lint::LateContext;
-use rustc_span::symbol::sym;
+use rustc_middle::hir::nested_filter;
+use rustc_span::{Span, sym};
+use std::ops::ControlFlow;
 
 use super::MAP_UNWRAP_OR;
 
-/// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
-///
-/// Returns true if the lint was emitted
+/// lint use of `map().unwrap_or()` for `Option`s and `Result`s
+#[expect(clippy::too_many_arguments)]
 pub(super) fn check<'tcx>(
     cx: &LateContext<'tcx>,
-    expr: &'tcx hir::Expr<'_>,
-    recv: &'tcx hir::Expr<'_>,
-    map_arg: &'tcx hir::Expr<'_>,
-    unwrap_arg: &'tcx hir::Expr<'_>,
+    expr: &rustc_hir::Expr<'_>,
+    recv: &rustc_hir::Expr<'_>,
+    map_arg: &'tcx rustc_hir::Expr<'_>,
+    unwrap_recv: &rustc_hir::Expr<'_>,
+    unwrap_arg: &'tcx rustc_hir::Expr<'_>,
+    map_span: Span,
     msrv: Msrv,
-) -> bool {
-    // lint if the caller of `map()` is an `Option` or a `Result`.
+) {
     let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option);
     let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result);
 
-    if is_result && !msrv.meets(cx, msrvs::RESULT_MAP_OR_ELSE) {
-        return false;
+    if is_result && !msrv.meets(cx, msrvs::RESULT_MAP_OR) {
+        return;
     }
 
+    // lint if the caller of `map()` is an `Option`
     if is_option || is_result {
-        // Don't make a suggestion that may fail to compile due to mutably borrowing
-        // the same variable twice.
-        let map_mutated_vars = mutated_variables(recv, cx);
-        let unwrap_mutated_vars = mutated_variables(unwrap_arg, cx);
-        if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
-            if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
-                return false;
+        if !is_copy(cx, cx.typeck_results().expr_ty(unwrap_arg)) {
+            // Replacing `.map(<f>).unwrap_or(<a>)` with `.map_or(<a>, <f>)` can sometimes lead to
+            // borrowck errors, see #10579 for one such instance.
+            // In particular, if `a` causes a move and `f` references that moved binding, then we cannot lint:
+            // ```
+            // let x = vec![1, 2];
+            // x.get(0..1).map(|s| s.to_vec()).unwrap_or(x);
+            // ```
+            // This compiles, but changing it to `map_or` will produce a compile error:
+            // ```
+            // let x = vec![1, 2];
+            // x.get(0..1).map_or(x, |s| s.to_vec())
+            //                    ^ moving `x` here
+            // ^^^^^^^^^^^ while it is borrowed here (and later used in the closure)
+            // ```
+            // So, we have to check that `a` is not referenced anywhere (even outside of the `.map` closure!)
+            // before the call to `unwrap_or`.
+
+            let mut unwrap_visitor = UnwrapVisitor {
+                cx,
+                identifiers: FxHashSet::default(),
+            };
+            unwrap_visitor.visit_expr(unwrap_arg);
+
+            let mut reference_visitor = ReferenceVisitor {
+                cx,
+                identifiers: unwrap_visitor.identifiers,
+                unwrap_or_span: unwrap_arg.span,
+            };
+
+            let body = cx.tcx.hir_body_owned_by(cx.tcx.hir_enclosing_body_owner(expr.hir_id));
+
+            // Visit the body, and return if we've found a reference
+            if reference_visitor.visit_body(body).is_break() {
+                return;
             }
-        } else {
-            return false;
         }
 
+        if !unwrap_arg.span.eq_ctxt(map_span) {
+            return;
+        }
+
+        // is_some_and is stabilised && `unwrap_or` argument is false; suggest `is_some_and` instead
+        let suggest_is_some_and = matches!(&unwrap_arg.kind, ExprKind::Lit(lit)
+            if matches!(lit.node, rustc_ast::LitKind::Bool(false)))
+            && msrv.meets(cx, msrvs::OPTION_RESULT_IS_VARIANT_AND);
+
+        let mut applicability = Applicability::MachineApplicable;
+        // get snippet for unwrap_or()
+        let unwrap_snippet = snippet_with_applicability(cx, unwrap_arg.span, "..", &mut applicability);
         // lint message
-        let msg = if is_option {
-            "called `map(<f>).unwrap_or_else(<g>)` on an `Option` value"
+        // comparing the snippet from source to raw text ("None") below is safe
+        // because we already have checked the type.
+        let unwrap_snippet_none = is_option && unwrap_snippet == "None";
+        let arg = if unwrap_snippet_none {
+            "None"
+        } else if suggest_is_some_and {
+            "false"
         } else {
-            "called `map(<f>).unwrap_or_else(<g>)` on a `Result` value"
+            "<a>"
         };
-        // get snippets for args to map() and unwrap_or_else()
-        let map_snippet = snippet(cx, map_arg.span, "..");
-        let unwrap_snippet = snippet(cx, unwrap_arg.span, "..");
-        // lint, with note if neither arg is > 1 line and both map() and
-        // unwrap_or_else() have the same span
-        let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
-        let same_span = map_arg.span.eq_ctxt(unwrap_arg.span);
-        if same_span && !multiline {
-            let var_snippet = snippet(cx, recv.span, "..");
-            span_lint_and_sugg(
-                cx,
-                MAP_UNWRAP_OR,
-                expr.span,
-                msg,
-                "try",
-                format!("{var_snippet}.map_or_else({unwrap_snippet}, {map_snippet})"),
-                Applicability::MachineApplicable,
-            );
-            return true;
-        } else if same_span && multiline {
-            span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
-            return true;
+        let suggest = if unwrap_snippet_none {
+            "and_then(<f>)"
+        } else if suggest_is_some_and {
+            if is_result {
+                "is_ok_and(<f>)"
+            } else {
+                "is_some_and(<f>)"
+            }
+        } else {
+            "map_or(<a>, <f>)"
+        };
+        let msg = format!(
+            "called `map(<f>).unwrap_or({arg})` on an `{}` value",
+            if is_option { "Option" } else { "Result" }
+        );
+
+        span_lint_and_then(cx, MAP_UNWRAP_OR, expr.span, msg, |diag| {
+            let map_arg_span = map_arg.span;
+
+            let mut suggestion = vec![
+                (
+                    map_span,
+                    String::from(if unwrap_snippet_none {
+                        "and_then"
+                    } else if suggest_is_some_and {
+                        if is_result { "is_ok_and" } else { "is_some_and" }
+                    } else {
+                        "map_or"
+                    }),
+                ),
+                (expr.span.with_lo(unwrap_recv.span.hi()), String::new()),
+            ];
+
+            if !unwrap_snippet_none && !suggest_is_some_and {
+                suggestion.push((map_arg_span.with_hi(map_arg_span.lo()), format!("{unwrap_snippet}, ")));
+            }
+
+            diag.multipart_suggestion(format!("use `{suggest}` instead"), suggestion, applicability);
+        });
+    }
+}
+
+struct UnwrapVisitor<'a, 'tcx> {
+    cx: &'a LateContext<'tcx>,
+    identifiers: FxHashSet<HirId>,
+}
+
+impl<'tcx> Visitor<'tcx> for UnwrapVisitor<'_, 'tcx> {
+    type NestedFilter = nested_filter::All;
+
+    fn visit_path(&mut self, path: &Path<'tcx>, _: HirId) {
+        if let Res::Local(local_id) = path.res
+            && let Node::Pat(pat) = self.cx.tcx.hir_node(local_id)
+            && let PatKind::Binding(_, local_id, ..) = pat.kind
+        {
+            self.identifiers.insert(local_id);
         }
+        walk_path(self, path);
     }
 
-    false
+    fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
+        self.cx.tcx
+    }
+}
+
+struct ReferenceVisitor<'a, 'tcx> {
+    cx: &'a LateContext<'tcx>,
+    identifiers: FxHashSet<HirId>,
+    unwrap_or_span: Span,
+}
+
+impl<'tcx> Visitor<'tcx> for ReferenceVisitor<'_, 'tcx> {
+    type NestedFilter = nested_filter::All;
+    type Result = ControlFlow<()>;
+    fn visit_expr(&mut self, expr: &'tcx rustc_hir::Expr<'_>) -> ControlFlow<()> {
+        // If we haven't found a reference yet, check if this references
+        // one of the locals that was moved in the `unwrap_or` argument.
+        // We are only interested in exprs that appear before the `unwrap_or` call.
+        if expr.span < self.unwrap_or_span
+            && let ExprKind::Path(ref path) = expr.kind
+            && let QPath::Resolved(_, path) = path
+            && let Res::Local(local_id) = path.res
+            && let Node::Pat(pat) = self.cx.tcx.hir_node(local_id)
+            && let PatKind::Binding(_, local_id, ..) = pat.kind
+            && self.identifiers.contains(&local_id)
+        {
+            return ControlFlow::Break(());
+        }
+        rustc_hir::intravisit::walk_expr(self, expr)
+    }
+
+    fn maybe_tcx(&mut self) -> Self::MaybeTyCtxt {
+        self.cx.tcx
+    }
 }

clippy_lints/src/methods/map_unwrap_or_else.rs

@@ -0,0 +1,77 @@
+use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
+use clippy_utils::msrvs::{self, Msrv};
+use clippy_utils::source::snippet;
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::usage::mutated_variables;
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
+
+use super::MAP_UNWRAP_OR;
+
+/// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
+///
+/// Returns true if the lint was emitted
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx hir::Expr<'_>,
+    recv: &'tcx hir::Expr<'_>,
+    map_arg: &'tcx hir::Expr<'_>,
+    unwrap_arg: &'tcx hir::Expr<'_>,
+    msrv: Msrv,
+) -> bool {
+    // lint if the caller of `map()` is an `Option` or a `Result`.
+    let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option);
+    let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result);
+
+    if is_result && !msrv.meets(cx, msrvs::RESULT_MAP_OR_ELSE) {
+        return false;
+    }
+
+    if is_option || is_result {
+        // Don't make a suggestion that may fail to compile due to mutably borrowing
+        // the same variable twice.
+        let map_mutated_vars = mutated_variables(recv, cx);
+        let unwrap_mutated_vars = mutated_variables(unwrap_arg, cx);
+        if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
+            if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
+                return false;
+            }
+        } else {
+            return false;
+        }
+
+        // lint message
+        let msg = if is_option {
+            "called `map(<f>).unwrap_or_else(<g>)` on an `Option` value"
+        } else {
+            "called `map(<f>).unwrap_or_else(<g>)` on a `Result` value"
+        };
+        // get snippets for args to map() and unwrap_or_else()
+        let map_snippet = snippet(cx, map_arg.span, "..");
+        let unwrap_snippet = snippet(cx, unwrap_arg.span, "..");
+        // lint, with note if neither arg is > 1 line and both map() and
+        // unwrap_or_else() have the same span
+        let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
+        let same_span = map_arg.span.eq_ctxt(unwrap_arg.span);
+        if same_span && !multiline {
+            let var_snippet = snippet(cx, recv.span, "..");
+            span_lint_and_sugg(
+                cx,
+                MAP_UNWRAP_OR,
+                expr.span,
+                msg,
+                "try",
+                format!("{var_snippet}.map_or_else({unwrap_snippet}, {map_snippet})"),
+                Applicability::MachineApplicable,
+            );
+            return true;
+        } else if same_span && multiline {
+            span_lint(cx, MAP_UNWRAP_OR, expr.span, msg);
+            return true;
+        }
+    }
+
+    false
+}

clippy_lints/src/methods/mod.rs

@@ -72,6 +72,7 @@ mod map_err_ignore;
 mod map_flatten;
 mod map_identity;
 mod map_unwrap_or;
+mod map_unwrap_or_else;
 mod map_with_unused_argument_over_ranges;
 mod mut_mutex_lock;
 mod needless_as_bytes;
@@ -86,7 +87,6 @@ mod open_options;
 mod option_as_ref_cloned;
 mod option_as_ref_deref;
 mod option_map_or_none;
-mod option_map_unwrap_or;
 mod or_fun_call;
 mod or_then_unwrap;
 mod path_buf_push_overwrite;
@@ -5551,7 +5551,7 @@ impl Methods {
                             );
                         },
                         Some((sym::map, m_recv, [m_arg], span, _)) => {
-                            option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span, self.msrv);
+                            map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span, self.msrv);
                         },
                         Some((then_method @ (sym::then | sym::then_some), t_recv, [t_arg], _, _)) => {
                             obfuscated_if_else::check(cx, expr, t_recv, t_arg, Some(u_arg), then_method, name);
@@ -5583,7 +5583,7 @@ impl Methods {
                 (sym::unwrap_or_else, [u_arg]) => {
                     match method_call(recv) {
                         Some((sym::map, recv, [map_arg], _, _))
-                            if map_unwrap_or::check(cx, expr, recv, map_arg, u_arg, self.msrv) => {},
+                            if map_unwrap_or_else::check(cx, expr, recv, map_arg, u_arg, self.msrv) => {},
                         Some((then_method @ (sym::then | sym::then_some), t_recv, [t_arg], _, _)) => {
                             obfuscated_if_else::check(
                                 cx,