Use try_eval_usize over eval_usize

Author: JohnTitor

clippy_lints/src/consts.rs

@@ -231,7 +231,13 @@ impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
             ExprKind::Tup(ref tup) => self.multi(tup).map(Constant::Tuple),
             ExprKind::Repeat(ref value, _) => {
                 let n = match self.tables.expr_ty(e).kind {
-                    ty::Array(_, n) => n.eval_usize(self.lcx.tcx, self.lcx.param_env),
+                    ty::Array(_, n) => {
+                        if let Some(n) = n.try_eval_usize(self.lcx.tcx, self.lcx.param_env) {
+                            n
+                        } else {
+                            return None;
+                        }
+                    },
                     _ => span_bug!(e.span, "typeck error"),
                 };
                 self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))

clippy_lints/src/indexing_slicing.rs

@@ -92,7 +92,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IndexingSlicing {
             if let Some(range) = higher::range(cx, index) {
                 // Ranged indexes, i.e., &x[n..m], &x[n..], &x[..n] and &x[..]
                 if let ty::Array(_, s) = ty.kind {
-                    let size: u128 = s.eval_usize(cx.tcx, cx.param_env).into();
+                    let size: u128 = if let Some(size) = s.try_eval_usize(cx.tcx, cx.param_env) {
+                        size.into()
+                    } else {
+                        return;
+                    };
 
                     let const_range = to_const_range(cx, range, size);
 

clippy_lints/src/methods/mod.rs

@@ -2324,7 +2324,13 @@ fn derefs_to_slice<'a, 'tcx>(
             ty::Slice(_) => true,
             ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
             ty::Adt(..) => is_type_diagnostic_item(cx, ty, Symbol::intern("vec_type")),
-            ty::Array(_, size) => size.eval_usize(cx.tcx, cx.param_env) < 32,
+            ty::Array(_, size) => {
+                if let Some(size) = size.try_eval_usize(cx.tcx, cx.param_env) {
+                    size < 32
+                } else {
+                    false
+                }
+            },
             ty::Ref(_, inner, _) => may_slice(cx, inner),
             _ => false,
         }