Rollup merge of #102406 - mejrs:missing_copy, r=wesleywiser

Make `missing_copy_implementations` more cautious

- Fixes https://github.com/rust-lang/rust/issues/98348
- Also makes the lint not fire on large types and types containing raw pointers. Thoughts?

1 files changed, 31 insertions, 1 deletions

diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index d0d34d8d2b4..08fbd973b06 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -53,7 +53,8 @@ use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, InnerSpan, Span};
 use rustc_target::abi::{Abi, VariantIdx};
-use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
+use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
+use rustc_trait_selection::traits::{self, misc::can_type_implement_copy, EvaluationResult};
 
 use crate::nonstandard_style::{method_context, MethodLateContext};
 
@@ -750,10 +751,39 @@ impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
         if def.has_dtor(cx.tcx) {
             return;
         }
+
+        // If the type contains a raw pointer, it may represent something like a handle,
+        // and recommending Copy might be a bad idea.
+        for field in def.all_fields() {
+            let did = field.did;
+            if cx.tcx.type_of(did).is_unsafe_ptr() {
+                return;
+            }
+        }
         let param_env = ty::ParamEnv::empty();
         if ty.is_copy_modulo_regions(cx.tcx, param_env) {
             return;
         }
+
+        // We shouldn't recommend implementing `Copy` on stateful things,
+        // such as iterators.
+        if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator) {
+            if cx.tcx.infer_ctxt().build().type_implements_trait(iter_trait, [ty], param_env)
+                == EvaluationResult::EvaluatedToOk
+            {
+                return;
+            }
+        }
+
+        // Default value of clippy::trivially_copy_pass_by_ref
+        const MAX_SIZE: u64 = 256;
+
+        if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
+            if size > MAX_SIZE {
+                return;
+            }
+        }
+
         if can_type_implement_copy(
             cx.tcx,
             param_env,