Merge ManualUnwrapOr into Matches lint pass

Author: Jarcho

clippy_lints/src/lib.register_all.rs

@@ -136,14 +136,14 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec![
     LintId::of(manual_map::MANUAL_MAP),
     LintId::of(manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
     LintId::of(manual_strip::MANUAL_STRIP),
-    LintId::of(manual_unwrap_or::MANUAL_UNWRAP_OR),
     LintId::of(map_clone::MAP_CLONE),
     LintId::of(map_unit_fn::OPTION_MAP_UNIT_FN),
     LintId::of(map_unit_fn::RESULT_MAP_UNIT_FN),
     LintId::of(match_result_ok::MATCH_RESULT_OK),
     LintId::of(match_str_case_mismatch::MATCH_STR_CASE_MISMATCH),
     LintId::of(matches::COLLAPSIBLE_MATCH),
     LintId::of(matches::INFALLIBLE_DESTRUCTURING_MATCH),
+    LintId::of(matches::MANUAL_UNWRAP_OR),
     LintId::of(matches::MATCH_AS_REF),
     LintId::of(matches::MATCH_LIKE_MATCHES_MACRO),
     LintId::of(matches::MATCH_OVERLAPPING_ARM),

clippy_lints/src/lib.register_complexity.rs

@@ -25,9 +25,9 @@ store.register_group(true, "clippy::complexity", Some("clippy_complexity"), vec!
     LintId::of(loops::SINGLE_ELEMENT_LOOP),
     LintId::of(loops::WHILE_LET_LOOP),
     LintId::of(manual_strip::MANUAL_STRIP),
-    LintId::of(manual_unwrap_or::MANUAL_UNWRAP_OR),
     LintId::of(map_unit_fn::OPTION_MAP_UNIT_FN),
     LintId::of(map_unit_fn::RESULT_MAP_UNIT_FN),
+    LintId::of(matches::MANUAL_UNWRAP_OR),
     LintId::of(matches::MATCH_AS_REF),
     LintId::of(matches::MATCH_SINGLE_BINDING),
     LintId::of(matches::NEEDLESS_MATCH),

clippy_lints/src/lib.register_lints.rs

@@ -254,7 +254,6 @@ store.register_lints(&[
     manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE,
     manual_ok_or::MANUAL_OK_OR,
     manual_strip::MANUAL_STRIP,
-    manual_unwrap_or::MANUAL_UNWRAP_OR,
     map_clone::MAP_CLONE,
     map_err_ignore::MAP_ERR_IGNORE,
     map_unit_fn::OPTION_MAP_UNIT_FN,
@@ -264,6 +263,7 @@ store.register_lints(&[
     match_str_case_mismatch::MATCH_STR_CASE_MISMATCH,
     matches::COLLAPSIBLE_MATCH,
     matches::INFALLIBLE_DESTRUCTURING_MATCH,
+    matches::MANUAL_UNWRAP_OR,
     matches::MATCH_AS_REF,
     matches::MATCH_BOOL,
     matches::MATCH_LIKE_MATCHES_MACRO,

clippy_lints/src/lib.rs

@@ -283,7 +283,6 @@ mod manual_map;
 mod manual_non_exhaustive;
 mod manual_ok_or;
 mod manual_strip;
-mod manual_unwrap_or;
 mod map_clone;
 mod map_err_ignore;
 mod map_unit_fn;
@@ -834,7 +833,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(repeat_once::RepeatOnce));
     store.register_late_pass(|| Box::new(unwrap_in_result::UnwrapInResult));
     store.register_late_pass(|| Box::new(self_assignment::SelfAssignment));
-    store.register_late_pass(|| Box::new(manual_unwrap_or::ManualUnwrapOr));
     store.register_late_pass(|| Box::new(manual_ok_or::ManualOkOr));
     store.register_late_pass(|| Box::new(float_equality_without_abs::FloatEqualityWithoutAbs));
     store.register_late_pass(|| Box::new(semicolon_if_nothing_returned::SemicolonIfNothingReturned));

clippy_lints/src/manual_unwrap_or.rs

@@ -0,0 +1,83 @@
+use clippy_utils::consts::constant_simple;
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::{indent_of, reindent_multiline, snippet_opt};
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::usage::contains_return_break_continue_macro;
+use clippy_utils::{is_lang_ctor, path_to_local_id, sugg};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::LangItem::{OptionNone, OptionSome, ResultErr, ResultOk};
+use rustc_hir::{Arm, Expr, PatKind};
+use rustc_lint::LateContext;
+use rustc_span::sym;
+
+use super::MANUAL_UNWRAP_OR;
+
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, scrutinee: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>]) {
+    let ty = cx.typeck_results().expr_ty(scrutinee);
+    if_chain! {
+        if let Some(ty_name) = if is_type_diagnostic_item(cx, ty, sym::Option) {
+            Some("Option")
+        } else if is_type_diagnostic_item(cx, ty, sym::Result) {
+            Some("Result")
+        } else {
+            None
+        };
+        if let Some(or_arm) = applicable_or_arm(cx, arms);
+        if let Some(or_body_snippet) = snippet_opt(cx, or_arm.body.span);
+        if let Some(indent) = indent_of(cx, expr.span);
+        if constant_simple(cx, cx.typeck_results(), or_arm.body).is_some();
+        then {
+            let reindented_or_body =
+                reindent_multiline(or_body_snippet.into(), true, Some(indent));
+
+            let suggestion = if scrutinee.span.from_expansion() {
+                    // we don't want parentheses around macro, e.g. `(some_macro!()).unwrap_or(0)`
+                    sugg::Sugg::hir_with_macro_callsite(cx, scrutinee, "..")
+                }
+                else {
+                    sugg::Sugg::hir(cx, scrutinee, "..").maybe_par()
+                };
+
+            span_lint_and_sugg(
+                cx,
+                MANUAL_UNWRAP_OR, expr.span,
+                &format!("this pattern reimplements `{}::unwrap_or`", ty_name),
+                "replace with",
+                format!(
+                    "{}.unwrap_or({})",
+                    suggestion,
+                    reindented_or_body,
+                ),
+                Applicability::MachineApplicable,
+            );
+        }
+    }
+}
+
+fn applicable_or_arm<'a>(cx: &LateContext<'_>, arms: &'a [Arm<'a>]) -> Option<&'a Arm<'a>> {
+    if_chain! {
+        if arms.len() == 2;
+        if arms.iter().all(|arm| arm.guard.is_none());
+        if let Some((idx, or_arm)) = arms.iter().enumerate().find(|(_, arm)| {
+            match arm.pat.kind {
+                PatKind::Path(ref qpath) => is_lang_ctor(cx, qpath, OptionNone),
+                PatKind::TupleStruct(ref qpath, [pat], _) =>
+                    matches!(pat.kind, PatKind::Wild) && is_lang_ctor(cx, qpath, ResultErr),
+                _ => false,
+            }
+        });
+        let unwrap_arm = &arms[1 - idx];
+        if let PatKind::TupleStruct(ref qpath, [unwrap_pat], _) = unwrap_arm.pat.kind;
+        if is_lang_ctor(cx, qpath, OptionSome) || is_lang_ctor(cx, qpath, ResultOk);
+        if let PatKind::Binding(_, binding_hir_id, ..) = unwrap_pat.kind;
+        if path_to_local_id(unwrap_arm.body, binding_hir_id);
+        if cx.typeck_results().expr_adjustments(unwrap_arm.body).is_empty();
+        if !contains_return_break_continue_macro(or_arm.body);
+        then {
+            Some(or_arm)
+        } else {
+            None
+        }
+    }
+}

clippy_lints/src/matches/manual_unwrap_or.rs

@@ -1,5 +1,5 @@
 use clippy_utils::source::{snippet_opt, span_starts_with, walk_span_to_context};
-use clippy_utils::{higher, meets_msrv, msrvs};
+use clippy_utils::{higher, in_constant, meets_msrv, msrvs};
 use rustc_hir::{Arm, Expr, ExprKind, Local, MatchSource, Pat};
 use rustc_lexer::{tokenize, TokenKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
@@ -10,6 +10,7 @@ use rustc_span::{Span, SpanData, SyntaxContext};
 
 mod collapsible_match;
 mod infallible_destructuring_match;
+mod manual_unwrap_or;
 mod match_as_ref;
 mod match_bool;
 mod match_like_matches;
@@ -650,6 +651,33 @@ declare_clippy_lint! {
     "Nested `match` or `if let` expressions where the patterns may be \"collapsed\" together."
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Finds patterns that reimplement `Option::unwrap_or` or `Result::unwrap_or`.
+    ///
+    /// ### Why is this bad?
+    /// Concise code helps focusing on behavior instead of boilerplate.
+    ///
+    /// ### Example
+    /// ```rust
+    /// let foo: Option<i32> = None;
+    /// match foo {
+    ///     Some(v) => v,
+    ///     None => 1,
+    /// };
+    /// ```
+    ///
+    /// Use instead:
+    /// ```rust
+    /// let foo: Option<i32> = None;
+    /// foo.unwrap_or(1);
+    /// ```
+    #[clippy::version = "1.49.0"]
+    pub MANUAL_UNWRAP_OR,
+    complexity,
+    "finds patterns that can be encoded more concisely with `Option::unwrap_or` or `Result::unwrap_or`"
+}
+
 #[derive(Default)]
 pub struct Matches {
     msrv: Option<RustcVersion>,
@@ -685,6 +713,7 @@ impl_lint_pass!(Matches => [
     MATCH_SAME_ARMS,
     NEEDLESS_MATCH,
     COLLAPSIBLE_MATCH,
+    MANUAL_UNWRAP_OR,
 ]);
 
 impl<'tcx> LateLintPass<'tcx> for Matches {
@@ -722,6 +751,10 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
                     match_as_ref::check(cx, ex, arms, expr);
                     needless_match::check_match(cx, ex, arms, expr);
 
+                    if !in_constant(cx, expr.hir_id) {
+                        manual_unwrap_or::check(cx, expr, ex, arms);
+                    }
+
                     if self.infallible_destructuring_match_linted {
                         self.infallible_destructuring_match_linted = false;
                     } else {