Allow all associated functions and add test

compiler/rustc_passes/messages.ftl

@@ -627,13 +627,9 @@ passes_attr_application_struct_enum_union =
     attribute should be applied to a struct, enum, or union
     .label = not a struct, enum, or union
 
-passes_attr_application_struct_enum_function_union =
+passes_attr_application_struct_enum_function_method_union =
-    attribute should be applied to a struct, enum, function, or union
+    attribute should be applied to a struct, enum, function, associated function, or union
-    .label = not a struct, enum, function, or union
+    .label = not a struct, enum, function, associated function, or union
-
-passes_attr_application_struct_enum_function_inherent_method_union =
-    attribute should be applied to a struct, enum, function, inherent method, or union
-    .label = not a struct, enum, function, inherent method, or union
 
 passes_transparent_incompatible =
     transparent {$target} cannot have other repr hints

compiler/rustc_passes/src/check_attr.rs

@@ -1745,10 +1745,10 @@ impl CheckAttrVisitor<'_> {
                         | Target::Union
                         | Target::Enum
                         | Target::Fn
-                        | Target::Method(MethodKind::Inherent) => continue,
+                        | Target::Method(_) => continue,
                         _ => {
                             self.tcx.sess.emit_err(
-                                errors::AttrApplication::StructEnumFunctionInherentMethodUnion {
+                                errors::AttrApplication::StructEnumFunctionMethodUnion {
                                     hint_span: hint.span(),
                                     span,
                                 },

compiler/rustc_passes/src/errors.rs

@@ -1355,8 +1355,8 @@ pub enum AttrApplication {
         #[label]
         span: Span,
     },
-    #[diag(passes_attr_application_struct_enum_function_inherent_method_union, code = "E0517")]
+    #[diag(passes_attr_application_struct_enum_function_method_union, code = "E0517")]
-    StructEnumFunctionInherentMethodUnion {
+    StructEnumFunctionMethodUnion {
         #[primary_span]
         hint_span: Span,
         #[label]

tests/codegen/align-fn.rs

@@ -15,4 +15,35 @@ impl A {
     #[no_mangle]
     #[repr(align(16))]
     pub fn method_align(self) {}
+
+    // CHECK: align 16
+    #[no_mangle]
+    #[repr(align(16))]
+    pub fn associated_fn() {}
+}
+
+trait T: Sized {
+    fn trait_fn() {}
+
+    // CHECK: align 32
+    #[repr(align(32))]
+    fn trait_method(self) {}
+}
+
+impl T for A {
+    // CHECK: align 16
+    #[no_mangle]
+    #[repr(align(16))]
+    fn trait_fn() {}
+
+    // CHECK: align 16
+    #[no_mangle]
+    #[repr(align(16))]
+    fn trait_method(self) {}
+}
+
+impl T for () {}
+
+pub fn foo() {
+    ().trait_method();
 }