Add TODO for const stability MSRV checking

Also, update error marker for consistency.

Author: samueltardieu

clippy_lints/src/incompatible_msrv.rs

@@ -168,6 +168,7 @@ impl IncompatibleMsrv {
 
 impl<'tcx> LateLintPass<'tcx> for IncompatibleMsrv {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        // TODO: check for const stability when in const context
         match expr.kind {
             ExprKind::MethodCall(_, _, _, span) => {
                 if let Some(method_did) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {

tests/ui/incompatible_msrv.rs

@@ -74,7 +74,7 @@ fn lang_items() {
 #[clippy::msrv = "1.80.0"]
 fn issue14212() {
     let _ = std::iter::repeat_n((), 5);
-    //~^ ERROR: is `1.80.0` but this item is stable since `1.82.0`
+    //~^ incompatible_msrv
 }
 
 fn local_msrv_change_suggestion() {