Fix test case for scenario that shouldn't be linted

Author: Yusuf Raji

clippy_lints/src/lib.rs

@@ -977,5 +977,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::new(unneeded_struct_pattern::UnneededStructPattern));
     store.register_late_pass(|_| Box::<unnecessary_semicolon::UnnecessarySemicolon>::default());
     store.register_late_pass(move |_| Box::new(non_std_lazy_statics::NonStdLazyStatic::new(conf)));
+    store.register_late_pass(|_| Box::new(single_option_map::SingleOptionMap));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

clippy_lints/src/single_option_map.rs

@@ -52,12 +52,13 @@ impl<'tcx> LateLintPass<'tcx> for SingleOptionMap {
             && matches!(kind, FnKind::ItemFn(_, _, _) | FnKind::Method(_, _))
         {
             let func_body = peel_blocks(body.value);
-            if let ExprKind::MethodCall(method_name, callee, _args, _span) = func_body.kind
+            if let ExprKind::MethodCall(method_name, callee, args, _span) = func_body.kind
                 && method_name.ident.name == sym::map
                 && let callee_type = cx.typeck_results().expr_ty(callee)
                 && is_type_diagnostic_item(cx, callee_type, sym::Option)
                 && let ExprKind::Path(_path) = callee.kind
                 && let Res::Local(_id) = path_res(cx, callee)
+                && !matches!(args[0].kind, ExprKind::Path(_))
             {
                 span_lint_and_help(
                     cx,

tests/ui/single_option_map.rs

@@ -2,7 +2,8 @@
 
 use std::sync::atomic::{AtomicUsize, Ordering};
 
-static MAYBE_ATOMIC: Option<AtomicUsize> = Some(AtomicUsize::new(42));
+static ATOM: AtomicUsize = AtomicUsize::new(42);
+static MAYBE_ATOMIC: Option<&AtomicUsize> = Some(&ATOM);
 
 fn h(arg: Option<u32>) -> Option<u32> {
     arg.map(|x| x * 2)
@@ -13,7 +14,7 @@ fn j(arg: Option<u64>) -> Option<u64> {
 }
 
 fn maps_static_option() -> Option<usize> {
-    MAYBE_ATOMIC.as_ref().map(|a| a.load(Ordering::Relaxed))
+    MAYBE_ATOMIC.map(|a| a.load(Ordering::Relaxed))
 }
 
 fn manipulate(i: i32) -> i32 {

tests/ui/single_option_map.stderr

@@ -0,0 +1,24 @@
+error: `fn` that only maps over argument
+  --> tests/ui/single_option_map.rs:8:1
+   |
+LL | / fn h(arg: Option<u32>) -> Option<u32> {
+LL | |     arg.map(|x| x * 2)
+LL | | }
+   | |_^
+   |
+   = help: move the `.map` to the caller or to an `_opt` function
+   = note: `-D clippy::single-option-map` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::single_option_map)]`
+
+error: `fn` that only maps over argument
+  --> tests/ui/single_option_map.rs:12:1
+   |
+LL | / fn j(arg: Option<u64>) -> Option<u64> {
+LL | |     arg.map(|x| x * 2)
+LL | | }
+   | |_^
+   |
+   = help: move the `.map` to the caller or to an `_opt` function
+
+error: aborting due to 2 previous errors
+