Fix manual_match with let-expressions

4 files changed, 191 insertions, 211 deletions

diff --git a/clippy_lints/src/collapsible_match.rs b/clippy_lints/src/collapsible_match.rs
index f5683856889..86226be715d 100644
--- a/clippy_lints/src/collapsible_match.rs
+++ b/clippy_lints/src/collapsible_match.rs
@@ -1,9 +1,10 @@
 use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::higher::IfLetOrMatch;
 use clippy_utils::visitors::is_local_used;
-use clippy_utils::{higher, is_lang_ctor, is_unit_expr, path_to_local, peel_ref_operators, SpanlessEq};
+use clippy_utils::{is_lang_ctor, is_unit_expr, path_to_local, peel_ref_operators, SpanlessEq};
 use if_chain::if_chain;
 use rustc_hir::LangItem::OptionNone;
-use rustc_hir::{Arm, Expr, ExprKind, Guard, HirId, MatchSource, Pat, PatKind, StmtKind};
+use rustc_hir::{Arm, Expr, ExprKind, Guard, HirId, Pat, PatKind, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{MultiSpan, Span};
@@ -149,33 +150,6 @@ fn strip_singleton_blocks<'hir>(mut expr: &'hir Expr<'hir>) -> &'hir Expr<'hir>
     expr
 }
 
-enum IfLetOrMatch<'hir> {
-    Match(&'hir Expr<'hir>, &'hir [Arm<'hir>], MatchSource),
-    /// scrutinee, pattern, then block, else block
-    IfLet(
-        &'hir Expr<'hir>,
-        &'hir Pat<'hir>,
-        &'hir Expr<'hir>,
-        Option<&'hir Expr<'hir>>,
-    ),
-}
-
-impl<'hir> IfLetOrMatch<'hir> {
-    fn parse(cx: &LateContext<'_>, expr: &Expr<'hir>) -> Option<Self> {
-        match expr.kind {
-            ExprKind::Match(expr, arms, source) => Some(Self::Match(expr, arms, source)),
-            _ => higher::IfLet::hir(cx, expr).map(
-                |higher::IfLet {
-                     let_expr,
-                     let_pat,
-                     if_then,
-                     if_else,
-                 }| { Self::IfLet(let_expr, let_pat, if_then, if_else) },
-            ),
-        }
-    }
-}
-
 /// A "wild-like" arm has a wild (`_`) or `None` pattern and no guard. Such arms can be "collapsed"
 /// into a single wild arm without any significant loss in semantics or readability.
 fn arm_is_wild_like(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
diff --git a/clippy_lints/src/manual_map.rs b/clippy_lints/src/manual_map.rs
index 385a3f546b9..b5f573cb104 100644
--- a/clippy_lints/src/manual_map.rs
+++ b/clippy_lints/src/manual_map.rs
@@ -1,6 +1,6 @@
 use crate::{map_unit_fn::OPTION_MAP_UNIT_FN, matches::MATCH_AS_REF};
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::higher;
+use clippy_utils::higher::IfLetOrMatch;
 use clippy_utils::source::{snippet_with_applicability, snippet_with_context};
 use clippy_utils::ty::{is_type_diagnostic_item, peel_mid_ty_refs_is_mutable};
 use clippy_utils::{
@@ -46,190 +46,169 @@ declare_lint_pass!(ManualMap => [MANUAL_MAP]);
 impl LateLintPass<'_> for ManualMap {
     #[allow(clippy::too_many_lines)]
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        if let Some(higher::IfLet {
-            let_pat,
-            let_expr,
-            if_then,
-            if_else: Some(if_else),
-        }) = higher::IfLet::hir(cx, expr)
-        {
-            manage_lint(cx, expr, (&let_pat.kind, if_then), (&PatKind::Wild, if_else), let_expr);
+        let (scrutinee, then_pat, then_body, else_pat, else_body) = match IfLetOrMatch::parse(cx, expr) {
+            Some(IfLetOrMatch::IfLet(scrutinee, pat, body, Some(r#else))) => (scrutinee, pat, body, None, r#else),
+            Some(IfLetOrMatch::Match(
+                scrutinee,
+                [arm1 @ Arm { guard: None, .. }, arm2 @ Arm { guard: None, .. }],
+                _,
+            )) => (scrutinee, arm1.pat, arm1.body, Some(arm2.pat), arm2.body),
+            _ => return,
+        };
+        if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
+            return;
         }
 
-        if let ExprKind::Match(scrutinee, [then @ Arm { guard: None, .. }, r#else @ Arm { guard: None, .. }], _) =
-            expr.kind
+        let (scrutinee_ty, ty_ref_count, ty_mutability) =
+            peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
+        if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
+            && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
         {
-            manage_lint(
-                cx,
-                expr,
-                (&then.pat.kind, then.body),
-                (&r#else.pat.kind, r#else.body),
-                scrutinee,
-            );
+            return;
         }
-    }
-}
-
-fn manage_lint<'tcx>(
-    cx: &LateContext<'tcx>,
-    expr: &'tcx Expr<'_>,
-    then: (&'tcx PatKind<'_>, &'tcx Expr<'_>),
-    r#else: (&'tcx PatKind<'_>, &'tcx Expr<'_>),
-    scrut: &'tcx Expr<'_>,
-) {
-    if in_external_macro(cx.sess(), expr.span) || in_constant(cx, expr.hir_id) {
-        return;
-    }
-
-    let (scrutinee_ty, ty_ref_count, ty_mutability) = peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrut));
-    if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
-        && is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
-    {
-        return;
-    }
-
-    let (then_pat, then_expr) = then;
-    let (else_pat, else_expr) = r#else;
 
-    let expr_ctxt = expr.span.ctxt();
-    let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
-        try_parse_pattern(cx, then_pat, expr_ctxt),
-        try_parse_pattern(cx, else_pat, expr_ctxt),
-    ) {
-        (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_expr) => {
-            (else_expr, pattern, ref_count, true)
-        },
-        (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_expr) => {
-            (else_expr, pattern, ref_count, false)
-        },
-        (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_expr) => {
-            (then_expr, pattern, ref_count, true)
-        },
-        (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_expr) => {
-            (then_expr, pattern, ref_count, false)
-        },
-        _ => return,
-    };
+        let expr_ctxt = expr.span.ctxt();
+        let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
+            try_parse_pattern(cx, then_pat, expr_ctxt),
+            else_pat.map_or(Some(OptionPat::Wild), |p| try_parse_pattern(cx, p, expr_ctxt)),
+        ) {
+            (Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
+                (else_body, pattern, ref_count, true)
+            },
+            (Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count })) if is_none_expr(cx, then_body) => {
+                (else_body, pattern, ref_count, false)
+            },
+            (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild)) if is_none_expr(cx, else_body) => {
+                (then_body, pattern, ref_count, true)
+            },
+            (Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None)) if is_none_expr(cx, else_body) => {
+                (then_body, pattern, ref_count, false)
+            },
+            _ => return,
+        };
 
-    // Top level or patterns aren't allowed in closures.
-    if matches!(some_pat.kind, PatKind::Or(_)) {
-        return;
-    }
+        // Top level or patterns aren't allowed in closures.
+        if matches!(some_pat.kind, PatKind::Or(_)) {
+            return;
+        }
 
-    let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
-        Some(expr) => expr,
-        None => return,
-    };
+        let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
+            Some(expr) => expr,
+            None => return,
+        };
 
-    if cx.typeck_results().expr_ty(some_expr) == cx.tcx.types.unit
-        && !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
-    {
-        return;
-    }
+        // These two lints will go back and forth with each other.
+        if cx.typeck_results().expr_ty(some_expr) == cx.tcx.types.unit
+            && !is_lint_allowed(cx, OPTION_MAP_UNIT_FN, expr.hir_id)
+        {
+            return;
+        }
 
-    // `map` won't perform any adjustments.
-    if !cx.typeck_results().expr_adjustments(some_expr).is_empty() {
-        return;
-    }
+        // `map` won't perform any adjustments.
+        if !cx.typeck_results().expr_adjustments(some_expr).is_empty() {
+            return;
+        }
 
-    // Determine which binding mode to use.
-    let explicit_ref = some_pat.contains_explicit_ref_binding();
-    let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
+        // Determine which binding mode to use.
+        let explicit_ref = some_pat.contains_explicit_ref_binding();
+        let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
 
-    let as_ref_str = match binding_ref {
-        Some(Mutability::Mut) => ".as_mut()",
-        Some(Mutability::Not) => ".as_ref()",
-        None => "",
-    };
+        let as_ref_str = match binding_ref {
+            Some(Mutability::Mut) => ".as_mut()",
+            Some(Mutability::Not) => ".as_ref()",
+            None => "",
+        };
 
-    match can_move_expr_to_closure(cx, some_expr) {
-        Some(captures) => {
-            // Check if captures the closure will need conflict with borrows made in the scrutinee.
-            // TODO: check all the references made in the scrutinee expression. This will require interacting
-            // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
-            if let Some(binding_ref_mutability) = binding_ref {
-                let e = peel_hir_expr_while(scrut, |e| match e.kind {
-                    ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
-                    _ => None,
-                });
-                if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
-                    match captures.get(l) {
-                        Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return,
-                        Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
-                            return;
-                        },
-                        Some(CaptureKind::Ref(Mutability::Not)) | None => (),
+        match can_move_expr_to_closure(cx, some_expr) {
+            Some(captures) => {
+                // Check if captures the closure will need conflict with borrows made in the scrutinee.
+                // TODO: check all the references made in the scrutinee expression. This will require interacting
+                // with the borrow checker. Currently only `<local>[.<field>]*` is checked for.
+                if let Some(binding_ref_mutability) = binding_ref {
+                    let e = peel_hir_expr_while(scrutinee, |e| match e.kind {
+                        ExprKind::Field(e, _) | ExprKind::AddrOf(_, _, e) => Some(e),
+                        _ => None,
+                    });
+                    if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(l), .. })) = e.kind {
+                        match captures.get(l) {
+                            Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return,
+                            Some(CaptureKind::Ref(Mutability::Not)) if binding_ref_mutability == Mutability::Mut => {
+                                return;
+                            },
+                            Some(CaptureKind::Ref(Mutability::Not)) | None => (),
+                        }
                     }
                 }
-            }
-        },
-        None => return,
-    };
-
-    let mut app = Applicability::MachineApplicable;
+            },
+            None => return,
+        };
 
-    // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
-    // it's being passed by value.
-    let scrutinee = peel_hir_expr_refs(scrut).0;
-    let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
-    let scrutinee_str = if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
-        format!("({})", scrutinee_str)
-    } else {
-        scrutinee_str.into()
-    };
+        let mut app = Applicability::MachineApplicable;
 
-    let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
-        match can_pass_as_func(cx, id, some_expr) {
-            Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
-                snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
-            },
-            _ => {
-                if path_to_local_id(some_expr, id)
-                    && !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
-                    && binding_ref.is_some()
-                {
-                    return;
-                }
+        // Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
+        // it's being passed by value.
+        let scrutinee = peel_hir_expr_refs(scrutinee).0;
+        let (scrutinee_str, _) = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
+        let scrutinee_str =
+            if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
+                format!("({})", scrutinee_str)
+            } else {
+                scrutinee_str.into()
+            };
 
-                // `ref` and `ref mut` annotations were handled earlier.
-                let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
-                    "mut "
-                } else {
-                    ""
-                };
-                format!(
-                    "|{}{}| {}",
-                    annotation,
-                    some_binding,
-                    snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
-                )
-            },
-        }
-    } else if !is_wild_none && explicit_ref.is_none() {
-        // TODO: handle explicit reference annotations.
-        format!(
-            "|{}| {}",
-            snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0,
-            snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
-        )
-    } else {
-        // Refutable bindings and mixed reference annotations can't be handled by `map`.
-        return;
-    };
+        let body_str = if let PatKind::Binding(annotation, id, some_binding, None) = some_pat.kind {
+            match can_pass_as_func(cx, id, some_expr) {
+                Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
+                    snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
+                },
+                _ => {
+                    if path_to_local_id(some_expr, id)
+                        && !is_lint_allowed(cx, MATCH_AS_REF, expr.hir_id)
+                        && binding_ref.is_some()
+                    {
+                        return;
+                    }
 
-    span_lint_and_sugg(
-        cx,
-        MANUAL_MAP,
-        expr.span,
-        "manual implementation of `Option::map`",
-        "try this",
-        if is_else_clause(cx.tcx, expr) {
-            format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
+                    // `ref` and `ref mut` annotations were handled earlier.
+                    let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
+                        "mut "
+                    } else {
+                        ""
+                    };
+                    format!(
+                        "|{}{}| {}",
+                        annotation,
+                        some_binding,
+                        snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
+                    )
+                },
+            }
+        } else if !is_wild_none && explicit_ref.is_none() {
+            // TODO: handle explicit reference annotations.
+            format!(
+                "|{}| {}",
+                snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app).0,
+                snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app).0
+            )
         } else {
-            format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
-        },
-        app,
-    );
+            // Refutable bindings and mixed reference annotations can't be handled by `map`.
+            return;
+        };
+
+        span_lint_and_sugg(
+            cx,
+            MANUAL_MAP,
+            expr.span,
+            "manual implementation of `Option::map`",
+            "try this",
+            if else_pat.is_none() && is_else_clause(cx.tcx, expr) {
+                format!("{{ {}{}.map({}) }}", scrutinee_str, as_ref_str, body_str)
+            } else {
+                format!("{}{}.map({})", scrutinee_str, as_ref_str, body_str)
+            },
+            app,
+        );
+    }
 }
 
 // Checks whether the expression could be passed as a function, or whether a closure is needed.
@@ -259,28 +238,21 @@ enum OptionPat<'a> {
 
 // Try to parse into a recognized `Option` pattern.
 // i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
-fn try_parse_pattern(
-    cx: &LateContext<'tcx>,
-    pat_kind: &'tcx PatKind<'_>,
-    ctxt: SyntaxContext,
-) -> Option<OptionPat<'tcx>> {
-    fn f(
-        cx: &LateContext<'tcx>,
-        pat_kind: &'tcx PatKind<'_>,
-        ref_count: usize,
-        ctxt: SyntaxContext,
-    ) -> Option<OptionPat<'tcx>> {
-        match pat_kind {
+fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
+    fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
+        match pat.kind {
             PatKind::Wild => Some(OptionPat::Wild),
-            PatKind::Ref(ref_pat, _) => f(cx, &ref_pat.kind, ref_count + 1, ctxt),
+            PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
             PatKind::Path(ref qpath) if is_lang_ctor(cx, qpath, OptionNone) => Some(OptionPat::None),
-            PatKind::TupleStruct(ref qpath, [pattern], _) if is_lang_ctor(cx, qpath, OptionSome) => {
+            PatKind::TupleStruct(ref qpath, [pattern], _)
+                if is_lang_ctor(cx, qpath, OptionSome) && pat.span.ctxt() == ctxt =>
+            {
                 Some(OptionPat::Some { pattern, ref_count })
             },
             _ => None,
         }
     }
-    f(cx, pat_kind, 0, ctxt)
+    f(cx, pat, 0, ctxt)
 }
 
 // Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
diff --git a/clippy_utils/src/higher.rs b/clippy_utils/src/higher.rs
index d20739a9f74..61e672781f8 100644
--- a/clippy_utils/src/higher.rs
+++ b/clippy_utils/src/higher.rs
@@ -6,7 +6,7 @@ use crate::{is_expn_of, match_def_path, paths};
 use if_chain::if_chain;
 use rustc_ast::ast::{self, LitKind};
 use rustc_hir as hir;
-use rustc_hir::{Block, BorrowKind, Expr, ExprKind, LoopSource, Node, Pat, StmtKind, UnOp};
+use rustc_hir::{Arm, Block, BorrowKind, Expr, ExprKind, LoopSource, MatchSource, Node, Pat, StmtKind, UnOp};
 use rustc_lint::LateContext;
 use rustc_span::{sym, ExpnKind, Span, Symbol};
 
@@ -115,6 +115,33 @@ impl<'hir> IfLet<'hir> {
     }
 }
 
+pub enum IfLetOrMatch<'hir> {
+    Match(&'hir Expr<'hir>, &'hir [Arm<'hir>], MatchSource),
+    /// scrutinee, pattern, then block, else block
+    IfLet(
+        &'hir Expr<'hir>,
+        &'hir Pat<'hir>,
+        &'hir Expr<'hir>,
+        Option<&'hir Expr<'hir>>,
+    ),
+}
+
+impl<'hir> IfLetOrMatch<'hir> {
+    pub fn parse(cx: &LateContext<'_>, expr: &Expr<'hir>) -> Option<Self> {
+        match expr.kind {
+            ExprKind::Match(expr, arms, source) => Some(Self::Match(expr, arms, source)),
+            _ => IfLet::hir(cx, expr).map(
+                |IfLet {
+                     let_expr,
+                     let_pat,
+                     if_then,
+                     if_else,
+                 }| { Self::IfLet(let_expr, let_pat, if_then, if_else) },
+            ),
+        }
+    }
+}
+
 pub struct IfOrIfLet<'hir> {
     pub cond: &'hir Expr<'hir>,
     pub r#else: Option<&'hir Expr<'hir>>,
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 7e03cf56e8a..6cecdd6b199 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -808,6 +808,13 @@ pub fn capture_local_usage(cx: &LateContext<'tcx>, e: &Expr<'_>) -> CaptureKind
                         capture_expr_ty = e;
                     }
                 },
+                ExprKind::Let(pat, ..) => {
+                    let mutability = match pat_capture_kind(cx, pat) {
+                        CaptureKind::Value => Mutability::Not,
+                        CaptureKind::Ref(m) => m,
+                    };
+                    return CaptureKind::Ref(mutability);
+                },
                 ExprKind::Match(_, arms, _) => {
                     let mut mutability = Mutability::Not;
                     for capture in arms.iter().map(|arm| pat_capture_kind(cx, arm.pat)) {