Factor out can_use_if_let_chains()

Author: samueltardieu

clippy_lints/src/collapsible_if.rs

@@ -1,8 +1,8 @@
 use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::msrvs::{self, Msrv};
+use clippy_utils::msrvs::Msrv;
 use clippy_utils::source::{IntoSpan as _, SpanRangeExt, snippet, snippet_block_with_applicability};
-use clippy_utils::{span_contains_non_whitespace, tokenize_with_text};
+use clippy_utils::{can_use_if_let_chains, span_contains_non_whitespace, tokenize_with_text};
 use rustc_ast::BinOpKind;
 use rustc_errors::Applicability;
 use rustc_hir::{Block, Expr, ExprKind, StmtKind};
@@ -216,8 +216,7 @@ impl CollapsibleIf {
     }
 
     fn eligible_condition(&self, cx: &LateContext<'_>, cond: &Expr<'_>) -> bool {
-        !matches!(cond.kind, ExprKind::Let(..))
-            || (cx.tcx.sess.edition().at_least_rust_2024() && self.msrv.meets(cx, msrvs::LET_CHAINS))
+        !matches!(cond.kind, ExprKind::Let(..)) || can_use_if_let_chains(cx, self.msrv)
     }
 }
 

clippy_utils/src/lib.rs

@@ -129,6 +129,7 @@ use visitors::{Visitable, for_each_unconsumed_temporary};
 use crate::ast_utils::unordered_over;
 use crate::consts::{ConstEvalCtxt, Constant, mir_to_const};
 use crate::higher::Range;
+use crate::msrvs::Msrv;
 use crate::ty::{adt_and_variant_of_res, can_partially_move_ty, expr_sig, is_copy, is_recursively_primitive_type};
 use crate::visitors::for_each_expr_without_closures;
 
@@ -3659,3 +3660,8 @@ pub fn is_expr_async_block(expr: &Expr<'_>) -> bool {
         })
     )
 }
+
+/// Checks if the chosen edition and `msrv` allows using `if let` chains.
+pub fn can_use_if_let_chains(cx: &LateContext<'_>, msrv: Msrv) -> bool {
+    cx.tcx.sess.edition().at_least_rust_2024() && msrv.meets(cx, msrvs::LET_CHAINS)
+}