rustc_pass_by_value lint: add test on custom types

compiler/rustc_lint/src/pass_by_value.rs

@@ -11,6 +11,7 @@ declare_tool_lint! {
     /// The `rustc_pass_by_value` lint marks a type with `#[rustc_pass_by_value]` requiring it to always be passed by value.
     /// This is usually used for types that are thin wrappers around references, so there is no benefit to an extra
     /// layer of indirection. (Example: `Ty` which is a reference to a `TyS`)
+    /// This lint relies on `#[rustc_diagnostic_item]` being available for the target.
     pub rustc::PASS_BY_VALUE,
     Warn,
     "pass by reference of a type flagged as `#[rustc_pass_by_value]`",

compiler/rustc_passes/src/check_attr.rs

@@ -1070,20 +1070,15 @@ impl CheckAttrVisitor<'_> {
     /// Warns against some misuses of `#[pass_by_value]`
     fn check_pass_by_value(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
         match target {
-            Target::Struct
+            Target::Struct | Target::Enum | Target::TyAlias => true,
-            | Target::Enum
-            | Target::Union
-            | Target::Trait
-            | Target::TraitAlias
-            | Target::TyAlias => true,
             _ => {
                 self.tcx
                     .sess
                     .struct_span_err(
                         attr.span,
-                        "`pass_by_value` attribute should be applied to a struct, enum, trait or type alias.",
+                        "`pass_by_value` attribute should be applied to a struct, enum or type alias.",
                     )
-                    .span_label(*span, "is not a struct, enum, trait or type alias")
+                    .span_label(*span, "is not a struct, enum or type alias")
                     .emit();
                 false
             }

src/test/ui-fulldeps/internal-lints/rustc_pass_by_value.rs

@@ -1,5 +1,6 @@
 // compile-flags: -Z unstable-options
 
+#![feature(rustc_attrs)]
 #![feature(rustc_private)]
 #![deny(rustc::pass_by_value)]
 #![allow(unused)]
@@ -61,4 +62,43 @@ impl Foo {
     //~^^ ERROR passing `TyCtxt<'_>` by reference
 }
 
+#[rustc_diagnostic_item = "CustomEnum"]
+#[rustc_pass_by_value]
+enum CustomEnum {
+    A,
+    B,
+}
+
+impl CustomEnum {
+    fn test(
+        value: CustomEnum,
+        reference: &CustomEnum, //~ ERROR passing `CustomEnum` by reference
+    ) {
+    }
+}
+
+#[rustc_diagnostic_item = "CustomStruct"]
+#[rustc_pass_by_value]
+struct CustomStruct {
+    s: u8,
+}
+
+#[rustc_diagnostic_item = "CustomAlias"]
+#[rustc_pass_by_value]
+type CustomAlias<'a> = &'a CustomStruct; //~ ERROR passing `CustomStruct` by reference
+
+impl CustomStruct {
+    fn test(
+        value: CustomStruct,
+        reference: &CustomStruct, //~ ERROR passing `CustomStruct` by reference
+    ) {
+    }
+
+    fn test_alias(
+        value: CustomAlias,
+        reference: &CustomAlias, //~ ERROR passing `CustomAlias<>` by reference
+    ) {
+    }
+}
+
 fn main() {}

src/test/ui-fulldeps/internal-lints/rustc_pass_by_value.stderr

@@ -1,80 +1,104 @@
 error: passing `Ty<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:13:13
+  --> $DIR/rustc_pass_by_value.rs:14:13
    |
 LL |     ty_ref: &Ty<'_>,
    |             ^^^^^^^ help: try passing by value: `Ty<'_>`
    |
 note: the lint level is defined here
-  --> $DIR/rustc_pass_by_value.rs:4:9
+  --> $DIR/rustc_pass_by_value.rs:5:9
    |
 LL | #![deny(rustc::pass_by_value)]
    |         ^^^^^^^^^^^^^^^^^^^^
 
 error: passing `TyCtxt<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:15:18
+  --> $DIR/rustc_pass_by_value.rs:16:18
    |
 LL |     ty_ctxt_ref: &TyCtxt<'_>,
    |                  ^^^^^^^^^^^ help: try passing by value: `TyCtxt<'_>`
 
 error: passing `Ty<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:19:28
+  --> $DIR/rustc_pass_by_value.rs:20:28
    |
 LL | fn ty_multi_ref(ty_multi: &&Ty<'_>, ty_ctxt_multi: &&&&TyCtxt<'_>) {}
    |                            ^^^^^^^ help: try passing by value: `Ty<'_>`
 
 error: passing `TyCtxt<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:19:55
+  --> $DIR/rustc_pass_by_value.rs:20:55
    |
 LL | fn ty_multi_ref(ty_multi: &&Ty<'_>, ty_ctxt_multi: &&&&TyCtxt<'_>) {}
    |                                                       ^^^^^^^^^^^ help: try passing by value: `TyCtxt<'_>`
 
 error: passing `Ty<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:26:17
+  --> $DIR/rustc_pass_by_value.rs:27:17
    |
 LL |         ty_ref: &Ty<'_>,
    |                 ^^^^^^^ help: try passing by value: `Ty<'_>`
 
 error: passing `TyCtxt<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:28:22
+  --> $DIR/rustc_pass_by_value.rs:29:22
    |
 LL |         ty_ctxt_ref: &TyCtxt<'_>,
    |                      ^^^^^^^^^^^ help: try passing by value: `TyCtxt<'_>`
 
 error: passing `Ty<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:31:41
+  --> $DIR/rustc_pass_by_value.rs:32:41
    |
 LL |     fn ty_multi_ref_in_trait(ty_multi: &&Ty<'_>, ty_ctxt_multi: &&&&TyCtxt<'_>);
    |                                         ^^^^^^^ help: try passing by value: `Ty<'_>`
 
 error: passing `TyCtxt<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:31:68
+  --> $DIR/rustc_pass_by_value.rs:32:68
    |
 LL |     fn ty_multi_ref_in_trait(ty_multi: &&Ty<'_>, ty_ctxt_multi: &&&&TyCtxt<'_>);
    |                                                                    ^^^^^^^^^^^ help: try passing by value: `TyCtxt<'_>`
 
 error: passing `Ty<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:53:17
+  --> $DIR/rustc_pass_by_value.rs:54:17
    |
 LL |         ty_ref: &Ty<'_>,
    |                 ^^^^^^^ help: try passing by value: `Ty<'_>`
 
 error: passing `TyCtxt<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:55:22
+  --> $DIR/rustc_pass_by_value.rs:56:22
    |
 LL |         ty_ctxt_ref: &TyCtxt<'_>,
    |                      ^^^^^^^^^^^ help: try passing by value: `TyCtxt<'_>`
 
 error: passing `Ty<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:59:38
+  --> $DIR/rustc_pass_by_value.rs:60:38
    |
 LL |     fn ty_multi_ref_assoc(ty_multi: &&Ty<'_>, ty_ctxt_multi: &&&&TyCtxt<'_>) {}
    |                                      ^^^^^^^ help: try passing by value: `Ty<'_>`
 
 error: passing `TyCtxt<'_>` by reference
-  --> $DIR/rustc_pass_by_value.rs:59:65
+  --> $DIR/rustc_pass_by_value.rs:60:65
    |
 LL |     fn ty_multi_ref_assoc(ty_multi: &&Ty<'_>, ty_ctxt_multi: &&&&TyCtxt<'_>) {}
    |                                                                 ^^^^^^^^^^^ help: try passing by value: `TyCtxt<'_>`
 
-error: aborting due to 12 previous errors
+error: passing `CustomEnum` by reference
+  --> $DIR/rustc_pass_by_value.rs:75:20
+   |
+LL |         reference: &CustomEnum,
+   |                    ^^^^^^^^^^^ help: try passing by value: `CustomEnum`
+
+error: passing `CustomStruct` by reference
+  --> $DIR/rustc_pass_by_value.rs:88:24
+   |
+LL | type CustomAlias<'a> = &'a CustomStruct;
+   |                        ^^^^^^^^^^^^^^^^ help: try passing by value: `CustomStruct`
+
+error: passing `CustomStruct` by reference
+  --> $DIR/rustc_pass_by_value.rs:93:20
+   |
+LL |         reference: &CustomStruct,
+   |                    ^^^^^^^^^^^^^ help: try passing by value: `CustomStruct`
+
+error: passing `CustomAlias<>` by reference
+  --> $DIR/rustc_pass_by_value.rs:99:20
+   |
+LL |         reference: &CustomAlias,
+   |                    ^^^^^^^^^^^^ help: try passing by value: `CustomAlias<>`
+
+error: aborting due to 16 previous errors