From 69c3e9c90f9a7731dcfe129b10e55e440ee6f484 Mon Sep 17 00:00:00 2001
From: Philipp Hansch <dev@phansch.net>
Date: Wed, 15 Apr 2020 09:55:02 +0200
Subject: [PATCH] large_enum_variant: Report sizes of variants
This reports the sizes of the largest and second-largest variants.
---
clippy_lints/src/large_enum_variant.rs | 25 +++++++++++++++++------
tests/ui/large_enum_variant.stderr | 28 ++++++++++++++++++++++----
2 files changed, 43 insertions(+), 10 deletions(-)
diff --git a/clippy_lints/src/large_enum_variant.rs b/clippy_lints/src/large_enum_variant.rs
index 00bbba64841..7ac83739be6 100644
--- a/clippy_lints/src/large_enum_variant.rs
+++ b/clippy_lints/src/large_enum_variant.rs
@@ -21,11 +21,19 @@ declare_clippy_lint! {
/// 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,
@@ -84,12 +92,21 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeEnumVariant {
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| {
+ db.span_label(
+ def.variants[(largest.1).0].span,
+ &format!("this variant is {} bytes", largest.0),
+ );
+ db.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, ..) => {
@@ -100,18 +117,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeEnumVariant {
if let Some(snip) = snippet_opt(cx, span) {
db.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",
- );
+ db.span_help(def.variants[i].span, help_text);
},
);
}
diff --git a/tests/ui/large_enum_variant.stderr b/tests/ui/large_enum_variant.stderr
index 5d659611533..8ce641a81f2 100644
--- a/tests/ui/large_enum_variant.stderr
+++ b/tests/ui/large_enum_variant.stderr
@@ -2,9 +2,14 @@ error: large size difference between variants
--> $DIR/large_enum_variant.rs:7:5
|
LL | B([i32; 8000]),
- | ^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^ this variant is 32000 bytes
|
= note: `-D clippy::large-enum-variant` implied by `-D warnings`
+note: and the second-largest variant is 4 bytes:
+ --> $DIR/large_enum_variant.rs:6:5
+ |
+LL | A(i32),
+ | ^^^^^^
help: consider boxing the large fields to reduce the total size of the enum
|
LL | B(Box<[i32; 8000]>),
@@ -14,8 +19,13 @@ error: large size difference between variants
--> $DIR/large_enum_variant.rs:31:5
|
LL | ContainingLargeEnum(LargeEnum),
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32004 bytes
|
+note: and the second-largest variant is 8 bytes:
+ --> $DIR/large_enum_variant.rs:30:5
+ |
+LL | VariantOk(i32, u32),
+ | ^^^^^^^^^^^^^^^^^^^
help: consider boxing the large fields to reduce the total size of the enum
|
LL | ContainingLargeEnum(Box<LargeEnum>),
@@ -25,8 +35,13 @@ error: large size difference between variants
--> $DIR/large_enum_variant.rs:41:5
|
LL | StructLikeLarge { x: [i32; 8000], y: i32 },
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32004 bytes
|
+note: and the second-largest variant is 8 bytes:
+ --> $DIR/large_enum_variant.rs:40:5
+ |
+LL | VariantOk(i32, u32),
+ | ^^^^^^^^^^^^^^^^^^^
help: consider boxing the large fields to reduce the total size of the enum
--> $DIR/large_enum_variant.rs:41:5
|
@@ -37,8 +52,13 @@ error: large size difference between variants
--> $DIR/large_enum_variant.rs:46:5
|
LL | StructLikeLarge2 { x: [i32; 8000] },
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32000 bytes
|
+note: and the second-largest variant is 8 bytes:
+ --> $DIR/large_enum_variant.rs:45:5
+ |
+LL | VariantOk(i32, u32),
+ | ^^^^^^^^^^^^^^^^^^^
help: consider boxing the large fields to reduce the total size of the enum
|
LL | StructLikeLarge2 { x: Box<[i32; 8000]> },