Replace some std::iter::repeat with str::repeat

[rust.git] / clippy_lints / src / large_enum_variant.rs

diff --git a/clippy_lints/src/large_enum_variant.rs b/clippy_lints/src/large_enum_variant.rs
index 00bbba64841a997b5eabd36c4f9d67c955413414..f166748d86b81a021822759440e66456206309b5 100644 (file)
--- a/clippy_lints/src/large_enum_variant.rs
+++ b/clippy_lints/src/large_enum_variant.rs
@@ -1,9 +1,11 @@
 //! lint when there is a large size difference between variants on an enum
 
-use crate::utils::{snippet_opt, span_lint_and_then};
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::source::snippet_opt;
 use rustc_errors::Applicability;
 use rustc_hir::{Item, ItemKind, VariantData};
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_target::abi::LayoutOf;
 
@@ -21,11 +23,19 @@
     /// measure the change this lint suggests.
     ///
     /// **Example:**
+    ///
     /// ```rust
+    /// // Bad
     /// enum Test {
     ///     A(i32),
     ///     B([i32; 8000]),
     /// }
+    ///
+    /// // Possibly better
+    /// enum Test2 {
+    ///     A(i32),
+    ///     B(Box<[i32; 8000]>),
+    /// }
     /// ```
     pub LARGE_ENUM_VARIANT,
     perf,
@@ -48,11 +58,13 @@ pub fn new(maximum_size_difference_allowed: u64) -> Self {
 
 impl_lint_pass!(LargeEnumVariant => [LARGE_ENUM_VARIANT]);
 
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeEnumVariant {
-    fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &Item<'_>) {
-        let did = cx.tcx.hir().local_def_id(item.hir_id);
+impl<'tcx> LateLintPass<'tcx> for LargeEnumVariant {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
+        if in_external_macro(cx.tcx.sess, item.span) {
+            return;
+        }
         if let ItemKind::Enum(ref def, _) = item.kind {
-            let ty = cx.tcx.type_of(did);
+            let ty = cx.tcx.type_of(item.def_id);
             let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
 
             let mut largest_variant: Option<(_, _)> = None;
@@ -84,34 +96,39 @@ fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &Item<'_>) {
                 if difference > self.maximum_size_difference_allowed {
                     let (i, variant) = largest.1;
 
+                    let help_text = "consider boxing the large fields to reduce the total size of the enum";
                     span_lint_and_then(
                         cx,
                         LARGE_ENUM_VARIANT,
                         def.variants[i].span,
                         "large size difference between variants",
-                        |db| {
+                        |diag| {
+                            diag.span_label(
+                                def.variants[(largest.1).0].span,
+                                &format!("this variant is {} bytes", largest.0),
+                            );
+                            diag.span_note(
+                                def.variants[(second.1).0].span,
+                                &format!("and the second-largest variant is {} bytes:", second.0),
+                            );
                             if variant.fields.len() == 1 {
                                 let span = match def.variants[i].data {
-                                    VariantData::Struct(ref fields, ..) | VariantData::Tuple(ref fields, ..) => {
+                                    VariantData::Struct(fields, ..) | VariantData::Tuple(fields, ..) => {
                                         fields[0].ty.span
                                     },
                                     VariantData::Unit(..) => unreachable!(),
                                 };
                                 if let Some(snip) = snippet_opt(cx, span) {
-                                    db.span_suggestion(
+                                    diag.span_suggestion(
                                         span,
-                                        "consider boxing the large fields to reduce the total size of the \
-                                         enum",
+                                        help_text,
                                         format!("Box<{}>", snip),
                                         Applicability::MaybeIncorrect,
                                     );
                                     return;
                                 }
                             }
-                            db.span_help(
-                                def.variants[i].span,
-                                "consider boxing the large fields to reduce the total size of the enum",
-                            );
+                            diag.span_help(def.variants[i].span, help_text);
                         },
                     );
                 }