Fix manual_match with let-expressions

Author: camsteffen

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};
@@ -150,33 +151,6 @@ 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 {