Fix check of immutable condition in closure

clippy_lints/src/loops.rs

@@ -2150,8 +2150,20 @@ fn check_infinite_loop<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, cond: &'tcx Expr, b
         return;
     }
 
+    if mut_var_visitor.ids.is_empty() {
+        span_lint(
+            cx,
+            WHILE_IMMUTABLE_CONDITION,
+            cond.span,
+            "all variables in condition are immutable. This either leads to an infinite or to a never running loop.",
+        );
+        return;
+    }
+
+
     let mut delegate = MutVarsDelegate {
         used_mutably: mut_var_visitor.ids,
+        skip: false,
     };
     let def_id = def_id::DefId::local(block.hir_id.owner);
     let region_scope_tree = &cx.tcx.region_scope_tree(def_id);
@@ -2194,7 +2206,10 @@ impl<'a, 'tcx> VarCollectorVisitor<'a, 'tcx> {
 impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'a, 'tcx> {
     fn visit_expr(&mut self, ex: &'tcx Expr) {
         match ex.node {
-            ExprPath(_) => self.insert_def_id(ex),
+            ExprPath(_) => if let Some(node_id) = check_for_mutability(self.cx, ex) {
+                self.ids.insert(node_id, false);
+            },
+
             // If there is any fuction/method call… we just stop analysis
             ExprCall(..) | ExprMethodCall(..) => self.skip = true,
 
@@ -2211,6 +2226,7 @@ impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'a, 'tcx> {
 
 struct MutVarsDelegate {
     used_mutably: HashMap<NodeId, bool>,
+    skip: bool,
 }
 
 impl<'tcx> MutVarsDelegate {
@@ -2220,6 +2236,7 @@ impl<'tcx> MutVarsDelegate {
                 if let Some(used) = self.used_mutably.get_mut(&id) {
                     *used = true;
                 },
+            Categorization::Upvar(_) => skip = true,
             Categorization::Deref(ref cmt, _) => self.update(&cmt.cat, sp),
             _ => {}
         }

tests/ui/infinite_loop.rs

@@ -1,9 +1,13 @@
+
+
+
 fn fn_val(i: i32) -> i32 { unimplemented!() }
 fn fn_constref(i: &i32) -> i32 { unimplemented!() }
 fn fn_mutref(i: &mut i32) { unimplemented!() }
 fn fooi() -> i32 { unimplemented!() }
 fn foob() -> bool { unimplemented!() }
 
+#[allow(many_single_char_names)]
 fn immutable_condition() {
     // Should warn when all vars mentionned are immutable
     let y = 0;
@@ -43,6 +47,14 @@ fn immutable_condition() {
         println!("OK - Fn call results may vary");
     }
 
+    let mut a = 0;
+    let mut c = move || {
+        while a < 5 {
+            a += 1;
+            println!("OK - a is mutable");
+        }
+    };
+    c();
 }
 
 fn unused_var() {