[`redundant_pattern_matching`]: catch `if let true`

clippy_lints/src/format_push_string.rs

@@ -57,7 +57,7 @@ fn is_format(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
             Some(higher::IfLetOrMatch::Match(_, arms, MatchSource::Normal)) => {
                 arms.iter().any(|arm| is_format(cx, arm.body))
             },
-            Some(higher::IfLetOrMatch::IfLet(_, _, then, r#else)) => {
+            Some(higher::IfLetOrMatch::IfLet(_, _, then, r#else, _)) => {
                 is_format(cx, then) || r#else.is_some_and(|e| is_format(cx, e))
             },
             _ => false,

clippy_lints/src/loops/manual_flatten.rs

@@ -20,7 +20,7 @@ pub(super) fn check<'tcx>(
     span: Span,
 ) {
     let inner_expr = peel_blocks_with_stmt(body);
-    if let Some(higher::IfLet { let_pat, let_expr, if_then, if_else: None })
+    if let Some(higher::IfLet { let_pat, let_expr, if_then, if_else: None, .. })
             = higher::IfLet::hir(cx, inner_expr)
         // Ensure match_expr in `if let` statement is the same as the pat from the for-loop
         && let PatKind::Binding(_, pat_hir_id, _, _) = pat.kind

clippy_lints/src/manual_let_else.rs

@@ -61,7 +61,7 @@ impl<'tcx> QuestionMark {
             && let Some(if_let_or_match) = IfLetOrMatch::parse(cx, init)
         {
             match if_let_or_match {
-                IfLetOrMatch::IfLet(if_let_expr, let_pat, if_then, if_else) => {
+                IfLetOrMatch::IfLet(if_let_expr, let_pat, if_then, if_else, ..) => {
                     if let Some(ident_map) = expr_simple_identity_map(local.pat, let_pat, if_then)
                         && let Some(if_else) = if_else
                         && is_never_expr(cx, if_else).is_some()

clippy_lints/src/matches/collapsible_match.rs

@@ -41,7 +41,7 @@ fn check_arm<'tcx>(
     let inner_expr = peel_blocks_with_stmt(outer_then_body);
     if let Some(inner) = IfLetOrMatch::parse(cx, inner_expr)
         && let Some((inner_scrutinee, inner_then_pat, inner_else_body)) = match inner {
-            IfLetOrMatch::IfLet(scrutinee, pat, _, els) => Some((scrutinee, pat, els)),
+            IfLetOrMatch::IfLet(scrutinee, pat, _, els, _) => Some((scrutinee, pat, els)),
             IfLetOrMatch::Match(scrutinee, arms, ..) => if arms.len() == 2 && arms.iter().all(|a| a.guard.is_none())
                 // if there are more than two arms, collapsing would be non-trivial
                 // one of the arms must be "wild-like"
@@ -75,7 +75,7 @@ fn check_arm<'tcx>(
         )
         // ...or anywhere in the inner expression
         && match inner {
-            IfLetOrMatch::IfLet(_, _, body, els) => {
+            IfLetOrMatch::IfLet(_, _, body, els, _) => {
                 !is_local_used(cx, body, binding_id) && els.map_or(true, |e| !is_local_used(cx, e, binding_id))
             },
             IfLetOrMatch::Match(_, arms, ..) => !arms.iter().any(|arm| is_local_used(cx, arm, binding_id)),

clippy_lints/src/matches/mod.rs

@@ -1104,6 +1104,7 @@ impl<'tcx> LateLintPass<'tcx> for Matches {
                     if_let.let_pat,
                     if_let.let_expr,
                     if_let.if_else.is_some(),
+                    if_let.let_span,
                 );
                 needless_match::check_if_let(cx, expr, &if_let);
             }

clippy_lints/src/matches/redundant_pattern_match.rs

@@ -12,13 +12,13 @@ use rustc_hir::LangItem::{self, OptionNone, OptionSome, PollPending, PollReady,
 use rustc_hir::{Arm, Expr, ExprKind, Guard, Node, Pat, PatKind, QPath, UnOp};
 use rustc_lint::LateContext;
 use rustc_middle::ty::{self, GenericArgKind, Ty};
-use rustc_span::{sym, Symbol};
+use rustc_span::{sym, Span, Symbol};
 use std::fmt::Write;
 use std::ops::ControlFlow;
 
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
     if let Some(higher::WhileLet { let_pat, let_expr, .. }) = higher::WhileLet::hir(expr) {
-        find_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
+        find_method_sugg_for_if_let(cx, expr, let_pat, let_expr, "while", false);
     }
 }
 
@@ -28,8 +28,34 @@ pub(super) fn check_if_let<'tcx>(
     pat: &'tcx Pat<'_>,
     scrutinee: &'tcx Expr<'_>,
     has_else: bool,
+    let_span: Span,
 ) {
-    find_sugg_for_if_let(cx, expr, pat, scrutinee, "if", has_else);
+    find_if_let_true(cx, pat, scrutinee, let_span);
+    find_method_sugg_for_if_let(cx, expr, pat, scrutinee, "if", has_else);
+}
+
+fn find_if_let_true<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, scrutinee: &'tcx Expr<'_>, let_span: Span) {
+    if let PatKind::Lit(lit) = pat.kind
+        && let ExprKind::Lit(lit) = lit.kind
+        && let LitKind::Bool(is_true) = lit.node
+    {
+        let mut snip = snippet(cx, scrutinee.span, "..").into_owned();
+
+        if !is_true {
+            // Invert condition for `if let false = ...`
+            snip.insert(0, '!');
+        }
+
+        span_lint_and_sugg(
+            cx,
+            REDUNDANT_PATTERN_MATCHING,
+            let_span,
+            "using `if let` to pattern match a boolean",
+            "consider using a regular `if` expression",
+            snip,
+            Applicability::MachineApplicable,
+        );
+    }
 }
 
 // Extract the generic arguments out of a type
@@ -100,7 +126,7 @@ fn find_method_and_type<'tcx>(
     }
 }
 
-fn find_sugg_for_if_let<'tcx>(
+fn find_method_sugg_for_if_let<'tcx>(
     cx: &LateContext<'tcx>,
     expr: &'tcx Expr<'_>,
     let_pat: &Pat<'_>,

clippy_lints/src/methods/filter_map.rs

@@ -186,7 +186,7 @@ impl<'tcx> OffendingFilterExpr<'tcx> {
                     match higher::IfLetOrMatch::parse(cx, map_body.value) {
                         // For `if let` we want to check that the variant matching arm references the local created by
                         // its pattern
-                        Some(higher::IfLetOrMatch::IfLet(sc, pat, then, Some(else_)))
+                        Some(higher::IfLetOrMatch::IfLet(sc, pat, then, Some(else_), ..))
                             if let Some((ident, span)) = expr_uses_local(pat, then) =>
                         {
                             (sc, else_, ident, span)

clippy_lints/src/option_if_let_else.rs

@@ -238,6 +238,7 @@ fn detect_option_if_let_else<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) ->
         let_expr,
         if_then,
         if_else: Some(if_else),
+        ..
     }) = higher::IfLet::hir(cx, expr)
         && !cx.typeck_results().expr_ty(expr).is_unit()
         && !is_else_clause(cx.tcx, expr)

clippy_lints/src/question_mark.rs

@@ -256,6 +256,7 @@ impl QuestionMark {
                 let_expr,
                 if_then,
                 if_else,
+                ..
             }) = higher::IfLet::hir(cx, expr)
             && !is_else_clause(cx.tcx, expr)
             && let PatKind::TupleStruct(ref path1, [field], ddpos) = let_pat.kind

clippy_utils/src/higher.rs

@@ -91,6 +91,9 @@ pub struct IfLet<'hir> {
     pub if_then: &'hir Expr<'hir>,
     /// `if let` else expression
     pub if_else: Option<&'hir Expr<'hir>>,
+    /// `if let PAT = EXPR`
+    ///     ^^^^^^^^^^^^^^
+    pub let_span: Span,
 }
 
 impl<'hir> IfLet<'hir> {
@@ -99,9 +102,10 @@ impl<'hir> IfLet<'hir> {
         if let ExprKind::If(
             Expr {
                 kind:
-                    ExprKind::Let(hir::Let {
+                    ExprKind::Let(&hir::Let {
                         pat: let_pat,
                         init: let_expr,
+                        span: let_span,
                         ..
                     }),
                 ..
@@ -129,6 +133,7 @@ impl<'hir> IfLet<'hir> {
                 let_expr,
                 if_then,
                 if_else,
+                let_span,
             });
         }
         None
@@ -146,6 +151,9 @@ pub enum IfLetOrMatch<'hir> {
         &'hir Pat<'hir>,
         &'hir Expr<'hir>,
         Option<&'hir Expr<'hir>>,
+        /// `if let PAT = EXPR`
+        ///     ^^^^^^^^^^^^^^
+        Span,
     ),
 }
 
@@ -160,7 +168,8 @@ impl<'hir> IfLetOrMatch<'hir> {
                      let_pat,
                      if_then,
                      if_else,
-                 }| { Self::IfLet(let_expr, let_pat, if_then, if_else) },
+                     let_span,
+                 }| { Self::IfLet(let_expr, let_pat, if_then, if_else, let_span) },
             ),
         }
     }