Add link to docs on malformed attributes

Author: estebank

compiler/rustc_feature/src/builtin_attrs.rs

@@ -349,6 +349,7 @@ lint_ill_formed_attribute_input = {$num_suggestions ->
         [1] attribute must be of the form {$suggestions}
         *[other] valid forms for the attribute are {$suggestions}
     }
+    .note = for more information, visit <{$docs}>
 
 lint_impl_trait_overcaptures = `{$self_ty}` will capture more lifetimes than possibly intended in edition 2024
     .note = specifically, {$num_captured ->

compiler/rustc_lint/messages.ftl

@@ -447,12 +447,14 @@ pub fn decorate_builtin_lint(
         BuiltinLintDiag::UnusedCrateDependency { extern_crate, local_crate } => {
             lints::UnusedCrateDependency { extern_crate, local_crate }.decorate_lint(diag)
         }
-        BuiltinLintDiag::IllFormedAttributeInput { suggestions } => {
+        BuiltinLintDiag::IllFormedAttributeInput { suggestions, docs } => {
             lints::IllFormedAttributeInput {
                 num_suggestions: suggestions.len(),
                 suggestions: DiagArgValue::StrListSepByAnd(
                     suggestions.into_iter().map(|s| format!("`{s}`").into()).collect(),
                 ),
+                has_docs: docs.is_some(),
+                docs: docs.unwrap_or(""),
             }
             .decorate_lint(diag)
         }

compiler/rustc_lint/src/early/diagnostics.rs

@@ -2685,6 +2685,9 @@ pub(crate) struct UnusedCrateDependency {
 pub(crate) struct IllFormedAttributeInput {
     pub num_suggestions: usize,
     pub suggestions: DiagArgValue,
+    #[note]
+    pub has_docs: bool,
+    pub docs: &'static str,
 }
 
 #[derive(LintDiagnostic)]

compiler/rustc_lint/src/lints.rs

@@ -793,6 +793,7 @@ pub enum BuiltinLintDiag {
     },
     IllFormedAttributeInput {
         suggestions: Vec<String>,
+        docs: Option<&'static str>,
     },
     InnerAttributeUnstable {
         is_macro: bool,

compiler/rustc_lint_defs/src/lib.rs

@@ -313,24 +313,27 @@ fn emit_malformed_attribute(
             ILL_FORMED_ATTRIBUTE_INPUT,
             span,
             ast::CRATE_NODE_ID,
-            BuiltinLintDiag::IllFormedAttributeInput { suggestions: suggestions.clone() },
+            BuiltinLintDiag::IllFormedAttributeInput {
+                suggestions: suggestions.clone(),
+                docs: template.docs,
+            },
         );
     } else {
         suggestions.sort();
-        psess
-            .dcx()
-            .struct_span_err(span, error_msg)
-            .with_span_suggestions(
-                span,
-                if suggestions.len() == 1 {
-                    "must be of the form"
-                } else {
-                    "the following are the possible correct uses"
-                },
-                suggestions,
-                Applicability::HasPlaceholders,
-            )
-            .emit();
+        let mut err = psess.dcx().struct_span_err(span, error_msg).with_span_suggestions(
+            span,
+            if suggestions.len() == 1 {
+                "must be of the form"
+            } else {
+                "the following are the possible correct uses"
+            },
+            suggestions,
+            Applicability::HasPlaceholders,
+        );
+        if let Some(link) = template.docs {
+            err.note(format!("for more information, visit <{link}>"));
+        }
+        err.emit();
     }
 }
 

compiler/rustc_parse/src/validate_attr.rs

@@ -3,6 +3,8 @@ error: malformed `crate_name` attribute input
    |
 LL | #![crate_name = concat!("my", "crate")]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#![crate_name = "name"]`
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/crates-and-source-files.html#the-crate_name-attribute>
 
 error: aborting due to 1 previous error
 

tests/ui/attributes/crate-name-macro-call.stderr

@@ -4,6 +4,7 @@ error: malformed `crate_type` attribute input
 LL | #![crate_type(lib)]
    | ^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/linkage.html>
 help: the following are the possible correct uses
    |
 LL - #![crate_type(lib)]

tests/ui/attributes/crate-type-delimited.stderr

@@ -4,6 +4,7 @@ error: malformed `crate_type` attribute input
 LL | #![crate_type]
    | ^^^^^^^^^^^^^^
    |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/linkage.html>
 help: the following are the possible correct uses
    |
 LL | #![crate_type = "bin"]

tests/ui/attributes/crate-type-empty.stderr

@@ -4,6 +4,7 @@ error: malformed `crate_type` attribute input
 LL | #![crate_type = foo!()]
    | ^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/linkage.html>
 help: the following are the possible correct uses
    |
 LL - #![crate_type = foo!()]