Lint `Option.map(f)` where f never returns

clippy_lints/src/map_nil_fn.rs

@@ -45,7 +45,7 @@ fn is_nil_function(cx: &LateContext, expr: &hir::Expr) -> bool {
 
     if let ty::TyFnDef(_, _, bare) = ty.sty {
         if let Some(fn_type) = cx.tcx.no_late_bound_regions(&bare.sig) {
-            return fn_type.output().is_nil();
+            return fn_type.output().is_nil() || fn_type.output().is_never();
         }
     }
     false

tests/compile-fail/map_nil_fn.rs

@@ -7,6 +7,10 @@
 
 fn do_nothing<T>(_: T) {}
 
+fn diverge<T>(_: T) -> ! {
+    panic!()
+}
+
 fn plus_one(value: usize) -> usize {
     value + 1
 }
@@ -39,4 +43,9 @@ fn main() {
     //~^ ERROR called `map(f)` on an Option value where `f` is a nil function
     //~| HELP try this
     //~| SUGGESTION if let Some(...) = x.field { do_nothing(...) }
+
+    x.field.map(diverge);
+    //~^ ERROR called `map(f)` on an Option value where `f` is a nil function
+    //~| HELP try this
+    //~| SUGGESTION if let Some(...) = x.field { diverge(...) }
 }