Fix misleading message when using a named constant as a struct alignment/pack

2 files changed, 40 insertions, 11 deletions

diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index f414ff746bb..6b6eefc64f8 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -1039,21 +1039,37 @@ pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
                             });
                         }
                     }
-                    MetaItemKind::List(_) => {
+                    MetaItemKind::List(nested_items) => {
                         if meta_item.has_name(sym::align) {
                             recognised = true;
-                            sess.dcx().emit_err(
-                                session_diagnostics::IncorrectReprFormatAlignOneArg {
-                                    span: meta_item.span,
-                                },
-                            );
+                            if nested_items.len() == 1 {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatExpectInteger {
+                                        span: nested_items[0].span(),
+                                    },
+                                );
+                            } else {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatAlignOneArg {
+                                        span: meta_item.span,
+                                    },
+                                );
+                            }
                         } else if meta_item.has_name(sym::packed) {
                             recognised = true;
-                            sess.dcx().emit_err(
-                                session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
-                                    span: meta_item.span,
-                                },
-                            );
+                            if nested_items.len() == 1 {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatPackedExpectInteger {
+                                        span: nested_items[0].span(),
+                                    },
+                                );
+                            } else {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
+                                        span: meta_item.span,
+                                    },
+                                );
+                            }
                         } else if matches!(
                             meta_item.name_or_empty(),
                             sym::Rust | sym::C | sym::simd | sym::transparent
diff --git a/compiler/rustc_attr/src/session_diagnostics.rs b/compiler/rustc_attr/src/session_diagnostics.rs
index 8cbd401d300..f489cc87bc7 100644
--- a/compiler/rustc_attr/src/session_diagnostics.rs
+++ b/compiler/rustc_attr/src/session_diagnostics.rs
@@ -170,6 +170,12 @@ pub(crate) struct IncorrectReprFormatPackedOneOrZeroArg {
     #[primary_span]
     pub span: Span,
 }
+#[derive(Diagnostic)]
+#[diag(attr_incorrect_repr_format_packed_expect_integer, code = E0552)]
+pub(crate) struct IncorrectReprFormatPackedExpectInteger {
+    #[primary_span]
+    pub span: Span,
+}
 
 #[derive(Diagnostic)]
 #[diag(attr_invalid_repr_hint_no_paren, code = E0552)]
@@ -253,6 +259,13 @@ pub(crate) struct IncorrectReprFormatAlignOneArg {
 }
 
 #[derive(Diagnostic)]
+#[diag(attr_incorrect_repr_format_expect_literal_integer, code = E0693)]
+pub(crate) struct IncorrectReprFormatExpectInteger {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(attr_incorrect_repr_format_generic, code = E0693)]
 pub(crate) struct IncorrectReprFormatGeneric<'a> {
     #[primary_span]