Stop using IllFormedAttributeInputLint for must_use

compiler/rustc_attr_parsing/messages.ftl

@@ -50,11 +50,6 @@ attr_parsing_expects_feature_list =
 attr_parsing_expects_features =
     `{$name}` expects feature names
 
-attr_parsing_ill_formed_attribute_input = {$num_suggestions ->
-        [1] attribute must be of the form {$suggestions}
-        *[other] valid forms for the attribute are {$suggestions}
-    }
-
 attr_parsing_import_name_type_raw =
     import name type can only be used with link kind `raw-dylib`
 

compiler/rustc_attr_parsing/src/attributes/must_use.rs

@@ -1,7 +1,4 @@
-use rustc_errors::DiagArgValue;
-
 use super::prelude::*;
-use crate::session_diagnostics::IllFormedAttributeInputLint;
 
 pub(crate) struct MustUseParser;
 
@@ -45,14 +42,7 @@ fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser) -> Option<Attrib
                     Some(value_str)
                 }
                 ArgParser::List(_) => {
-                    let suggestions = cx.suggestions();
-                    cx.emit_err(IllFormedAttributeInputLint {
-                        num_suggestions: suggestions.len(),
-                        suggestions: DiagArgValue::StrListSepByAnd(
-                            suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
-                        ),
-                        span: cx.attr_span,
-                    });
+                    cx.expected_name_value(cx.attr_span, None);
                     return None;
                 }
             },

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -380,15 +380,6 @@ pub(crate) struct UnusedMultiple {
     pub name: Symbol,
 }
 
-#[derive(Diagnostic)]
-#[diag(attr_parsing_ill_formed_attribute_input)]
-pub(crate) struct IllFormedAttributeInputLint {
-    #[primary_span]
-    pub span: Span,
-    pub num_suggestions: usize,
-    pub suggestions: DiagArgValue,
-}
-
 #[derive(Diagnostic)]
 #[diag(attr_parsing_null_on_export, code = E0648)]
 pub(crate) struct NullOnExport {

tests/ui/attributes/malformed-attrs.rs

@@ -59,7 +59,7 @@
 #[cold = 1]
 //~^ ERROR malformed
 #[must_use()]
-//~^ ERROR valid forms for the attribute are
+//~^ ERROR malformed
 #[no_mangle = 1]
 //~^ ERROR malformed
 #[unsafe(naked())]

tests/ui/attributes/malformed-attrs.stderr

@@ -314,11 +314,21 @@ LL | #[cold = 1]
    | |      didn't expect any arguments here
    | help: must be of the form: `#[cold]`
 
-error: valid forms for the attribute are `#[must_use = "reason"]` and `#[must_use]`
+error[E0539]: malformed `must_use` attribute input
   --> $DIR/malformed-attrs.rs:61:1
    |
 LL | #[must_use()]
    | ^^^^^^^^^^^^^
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute>
+help: try changing it to one of the following valid forms of the attribute
+   |
+LL - #[must_use()]
+LL + #[must_use = "reason"]
+   |
+LL - #[must_use()]
+LL + #[must_use]
+   |
 
 error[E0565]: malformed `no_mangle` attribute input
   --> $DIR/malformed-attrs.rs:63:1

tests/ui/attributes/malformed-must_use.rs

@@ -1,4 +1,4 @@
-#[must_use()] //~ ERROR valid forms for the attribute are `#[must_use = "reason"]` and `#[must_use]`
+#[must_use()] //~ ERROR malformed
 struct Test;
 
 fn main() {}

tests/ui/attributes/malformed-must_use.stderr

@@ -1,8 +1,19 @@
-error: valid forms for the attribute are `#[must_use = "reason"]` and `#[must_use]`
+error[E0539]: malformed `must_use` attribute input
   --> $DIR/malformed-must_use.rs:1:1
    |
 LL | #[must_use()]
    | ^^^^^^^^^^^^^
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute>
+help: try changing it to one of the following valid forms of the attribute
+   |
+LL - #[must_use()]
+LL + #[must_use = "reason"]
+   |
+LL - #[must_use()]
+LL + #[must_use]
+   |
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0539`.