From a3d373551551bc1bd5a993d586f42144f0f4542a Mon Sep 17 00:00:00 2001
From: surechen <chenshuo17@huawei.com>
Date: Sat, 18 Sep 2021 18:35:17 +0800
Subject: [PATCH] Arrays of sizes from 0 to 32 (inclusive) implement [Default]
 trait, edit method is_default_equivalent() to satisfy with this.

---
 clippy_utils/src/lib.rs         | 12 +++++++++++-
 tests/ui/derivable_impls.rs     | 20 ++++++++++++++++++++
 tests/ui/derivable_impls.stderr | 14 +++++++++++++-
 3 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 757485d19..903b61635 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -684,7 +684,17 @@ pub fn is_default_equivalent(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
             _ => false,
         },
         ExprKind::Tup(items) | ExprKind::Array(items) => items.iter().all(|x| is_default_equivalent(cx, x)),
-        ExprKind::Repeat(x, _) => is_default_equivalent(cx, x),
+        ExprKind::Repeat(x, y) => if_chain! {
+            if let ExprKind::Lit(ref const_lit) = cx.tcx.hir().body(y.body).value.kind;
+            if let LitKind::Int(v, _) = const_lit.node;
+            if v <= 32 && is_default_equivalent(cx, x);
+            then {
+                true
+            }
+            else {
+                false
+            }
+        },
         ExprKind::Call(repl_func, _) => if_chain! {
             if let ExprKind::Path(ref repl_func_qpath) = repl_func.kind;
             if let Some(repl_def_id) = cx.qpath_res(repl_func_qpath, repl_func.hir_id).opt_def_id();
diff --git a/tests/ui/derivable_impls.rs b/tests/ui/derivable_impls.rs
index ebbc0c77e..3eeebc117 100644
--- a/tests/ui/derivable_impls.rs
+++ b/tests/ui/derivable_impls.rs
@@ -207,4 +207,24 @@ impl Default for Color2 {
     }
 }
 
+pub struct RepeatDefault1 {
+    a: [i8; 32],
+}
+
+impl Default for RepeatDefault1 {
+    fn default() -> Self {
+        RepeatDefault1 { a: [0; 32] }
+    }
+}
+
+pub struct RepeatDefault2 {
+    a: [i8; 33],
+}
+
+impl Default for RepeatDefault2 {
+    fn default() -> Self {
+        RepeatDefault2 { a: [0; 33] }
+    }
+}
+
 fn main() {}
diff --git a/tests/ui/derivable_impls.stderr b/tests/ui/derivable_impls.stderr
index 4ed64fade..49fb471a2 100644
--- a/tests/ui/derivable_impls.stderr
+++ b/tests/ui/derivable_impls.stderr
@@ -73,5 +73,17 @@ LL | | }
    |
    = help: try annotating `WithoutSelfParan` with `#[derive(Default)]`
 
-error: aborting due to 6 previous errors
+error: this `impl` can be derived
+  --> $DIR/derivable_impls.rs:214:1
+   |
+LL | / impl Default for RepeatDefault1 {
+LL | |     fn default() -> Self {
+LL | |         RepeatDefault1 { a: [0; 32] }
+LL | |     }
+LL | | }
+   | |_^
+   |
+   = help: try annotating `RepeatDefault1` with `#[derive(Default)]`
+
+error: aborting due to 7 previous errors