Refactoring to use `constant_context

Use `constant_context`, `.is_str()` and `builtin_index()` to simplify.

Author: giraffate

clippy_lints/src/repeat_once.rs

@@ -1,12 +1,9 @@
-use crate::consts::{miri_to_const, Constant};
+use crate::consts::{constant_context, Constant};
 use crate::utils::{in_macro, is_type_diagnostic_item, snippet, span_lint_and_sugg, walk_ptrs_ty};
 use if_chain::if_chain;
-use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
-use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
@@ -44,10 +41,11 @@ impl<'tcx> LateLintPass<'tcx> for RepeatOnce {
         if_chain! {
             if let ExprKind::MethodCall(ref path, _, ref args, _) = expr.kind;
             if path.ident.name == sym!(repeat);
-            if is_once(cx, &args[1]) && !in_macro(args[0].span);
+            if let Some(Constant::Int(1)) = constant_context(cx, cx.tables()).expr(&args[1]);
+            if !in_macro(args[0].span);
             then {
                 let ty = walk_ptrs_ty(cx.tables().expr_ty(&args[0]));
-                if is_str(ty){
+                if ty.is_str() {
                     span_lint_and_sugg(
                         cx,
                         REPEAT_ONCE,
@@ -57,7 +55,7 @@ impl<'tcx> LateLintPass<'tcx> for RepeatOnce {
                         format!("{}.to_string()", snippet(cx, args[0].span, r#""...""#)),
                         Applicability::MachineApplicable,
                     );
-                } else if is_slice(ty) {
+                } else if let Some(_) = ty.builtin_index() {
                     span_lint_and_sugg(
                         cx,
                         REPEAT_ONCE,
@@ -82,45 +80,3 @@ impl<'tcx> LateLintPass<'tcx> for RepeatOnce {
         }
     }
 }
-
-fn is_once<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> bool {
-    match expr.kind {
-        ExprKind::Lit(ref lit) => {
-            if let LitKind::Int(ref lit_content, _) = lit.node {
-                *lit_content == 1
-            } else {
-                false
-            }
-        },
-        ExprKind::Path(rustc_hir::QPath::Resolved(None, path)) => {
-            if let Res::Def(DefKind::Const, def_id) = path.res {
-                let ty = cx.tcx.type_of(def_id);
-                let con = cx
-                    .tcx
-                    .const_eval_poly(def_id)
-                    .ok()
-                    .map(|val| rustc_middle::ty::Const::from_value(cx.tcx, val, ty))
-                    .unwrap();
-                let con = miri_to_const(con);
-                con == Some(Constant::Int(1))
-            } else {
-                false
-            }
-        },
-        _ => false,
-    }
-}
-
-fn is_str(ty: Ty<'_>) -> bool {
-    match ty.kind {
-        ty::Str => true,
-        _ => false,
-    }
-}
-
-fn is_slice(ty: Ty<'_>) -> bool {
-    match ty.kind {
-        ty::Slice(..) | ty::Array(..) => true,
-        _ => false,
-    }
-}