Do not suggest using a if let chain if it is not supported

This might be due to a low edition (< 2024) or too low a MSRV.

Author: samueltardieu

book/src/lint_configuration.md

@@ -897,6 +897,7 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
 * [`unchecked_duration_subtraction`](https://rust-lang.github.io/rust-clippy/master/index.html#unchecked_duration_subtraction)
 * [`uninlined_format_args`](https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args)
 * [`unnecessary_lazy_evaluations`](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_lazy_evaluations)
+* [`unnecessary_unwrap`](https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_unwrap)
 * [`unnested_or_patterns`](https://rust-lang.github.io/rust-clippy/master/index.html#unnested_or_patterns)
 * [`unused_trait_names`](https://rust-lang.github.io/rust-clippy/master/index.html#unused_trait_names)
 * [`use_self`](https://rust-lang.github.io/rust-clippy/master/index.html#use_self)

clippy_config/src/conf.rs

@@ -793,6 +793,7 @@ define_Conf! {
         unchecked_duration_subtraction,
         uninlined_format_args,
         unnecessary_lazy_evaluations,
+        unnecessary_unwrap,
         unnested_or_patterns,
         unused_trait_names,
         use_self,

clippy_lints/src/lib.rs

@@ -589,7 +589,7 @@ pub fn register_lint_passes(store: &mut rustc_lint::LintStore, conf: &'static Co
     store.register_late_pass(|_| Box::new(map_unit_fn::MapUnit));
     store.register_late_pass(|_| Box::new(inherent_impl::MultipleInherentImpl));
     store.register_late_pass(|_| Box::new(neg_cmp_op_on_partial_ord::NoNegCompOpForPartialOrd));
-    store.register_late_pass(|_| Box::new(unwrap::Unwrap));
+    store.register_late_pass(move |_| Box::new(unwrap::Unwrap::new(conf)));
     store.register_late_pass(move |_| Box::new(indexing_slicing::IndexingSlicing::new(conf)));
     store.register_late_pass(move |tcx| Box::new(non_copy_const::NonCopyConst::new(tcx, conf)));
     store.register_late_pass(|_| Box::new(redundant_clone::RedundantClone));

clippy_lints/src/unwrap.rs

@@ -1,7 +1,9 @@
+use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint_hir_and_then;
+use clippy_utils::msrvs::Msrv;
 use clippy_utils::ty::get_type_diagnostic_name;
 use clippy_utils::usage::is_potentially_local_place;
-use clippy_utils::{higher, path_to_local, sym};
+use clippy_utils::{can_use_if_let_chains, higher, path_to_local, sym};
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{FnKind, Visitor, walk_expr, walk_fn};
 use rustc_hir::{BinOpKind, Body, Expr, ExprKind, FnDecl, HirId, Node, UnOp};
@@ -10,7 +12,7 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::mir::FakeReadCause;
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_session::declare_lint_pass;
+use rustc_session::impl_lint_pass;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{Span, Symbol};
 
@@ -72,10 +74,21 @@ declare_clippy_lint! {
     "checks for calls of `unwrap[_err]()` that will always fail"
 }
 
+pub(crate) struct Unwrap {
+    msrv: Msrv,
+}
+
+impl Unwrap {
+    pub fn new(conf: &'static Conf) -> Self {
+        Self { msrv: conf.msrv }
+    }
+}
+
 /// Visitor that keeps track of which variables are unwrappable.
-struct UnwrappableVariablesVisitor<'a, 'tcx> {
+struct UnwrappableVariablesVisitor<'a, 'tcx, 'unwrap> {
     unwrappables: Vec<UnwrapInfo<'tcx>>,
     cx: &'a LateContext<'tcx>,
+    unwrap: &'unwrap Unwrap,
 }
 
 /// What kind of unwrappable this is.
@@ -231,7 +244,7 @@ impl<'tcx> Delegate<'tcx> for MutationVisitor<'tcx> {
     fn fake_read(&mut self, _: &PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
 }
 
-impl<'tcx> UnwrappableVariablesVisitor<'_, 'tcx> {
+impl<'tcx> UnwrappableVariablesVisitor<'_, 'tcx, '_> {
     fn visit_branch(
         &mut self,
         if_expr: &'tcx Expr<'_>,
@@ -282,7 +295,7 @@ fn consume_option_as_ref<'tcx>(expr: &'tcx Expr<'tcx>) -> (&'tcx Expr<'tcx>, Opt
     }
 }
 
-impl<'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'_, 'tcx> {
+impl<'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'_, 'tcx, '_> {
     type NestedFilter = nested_filter::OnlyBodies;
 
     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
@@ -353,7 +366,11 @@ impl<'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'_, 'tcx> {
                                 );
                             } else {
                                 diag.span_label(unwrappable.check.span, "the check is happening here");
-                                diag.help("try using `if let` or `match`");
+                                if can_use_if_let_chains(self.cx, self.unwrap.msrv) {
+                                    diag.help("try using `if let` or `match`");
+                                } else {
+                                    diag.help("try using `match`");
+                                }
                             }
                         },
                     );
@@ -379,7 +396,7 @@ impl<'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'_, 'tcx> {
     }
 }
 
-declare_lint_pass!(Unwrap => [PANICKING_UNWRAP, UNNECESSARY_UNWRAP]);
+impl_lint_pass!(Unwrap => [PANICKING_UNWRAP, UNNECESSARY_UNWRAP]);
 
 impl<'tcx> LateLintPass<'tcx> for Unwrap {
     fn check_fn(
@@ -398,6 +415,7 @@ impl<'tcx> LateLintPass<'tcx> for Unwrap {
         let mut v = UnwrappableVariablesVisitor {
             unwrappables: Vec::new(),
             cx,
+            unwrap: self,
         };
 
         walk_fn(&mut v, kind, decl, body.id(), fn_id);

tests/ui/checked_unwrap/if_let_chains.rs

@@ -0,0 +1,24 @@
+//@require-annotations-for-level: ERROR
+#![deny(clippy::unnecessary_unwrap)]
+
+#[clippy::msrv = "1.85"]
+fn if_let_chains_unsupported(a: Option<u32>, b: Option<u32>) {
+    if a.is_none() || b.is_none() {
+        println!("a or b is not set");
+    } else {
+        println!("the value of a is {}", a.unwrap());
+        //~^ unnecessary_unwrap
+        //~| HELP: try using `match`
+    }
+}
+
+#[clippy::msrv = "1.88"]
+fn if_let_chains_supported(a: Option<u32>, b: Option<u32>) {
+    if a.is_none() || b.is_none() {
+        println!("a or b is not set");
+    } else {
+        println!("the value of a is {}", a.unwrap());
+        //~^ unnecessary_unwrap
+        //~| HELP: try using `if let` or `match`
+    }
+}

tests/ui/checked_unwrap/if_let_chains.stderr

@@ -0,0 +1,29 @@
+error: called `unwrap` on `a` after checking its variant with `is_none`
+  --> tests/ui/checked_unwrap/if_let_chains.rs:9:42
+   |
+LL |     if a.is_none() || b.is_none() {
+   |        ----------- the check is happening here
+...
+LL |         println!("the value of a is {}", a.unwrap());
+   |                                          ^^^^^^^^^^
+   |
+   = help: try using `match`
+note: the lint level is defined here
+  --> tests/ui/checked_unwrap/if_let_chains.rs:2:9
+   |
+LL | #![deny(clippy::unnecessary_unwrap)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: called `unwrap` on `a` after checking its variant with `is_none`
+  --> tests/ui/checked_unwrap/if_let_chains.rs:20:42
+   |
+LL |     if a.is_none() || b.is_none() {
+   |        ----------- the check is happening here
+...
+LL |         println!("the value of a is {}", a.unwrap());
+   |                                          ^^^^^^^^^^
+   |
+   = help: try using `if let` or `match`
+
+error: aborting due to 2 previous errors
+