JonathanBrouwer · Oct 26, 2026 · Oct 27, 2026 · Oct 27, 2026
diff --git a/compiler/rustc_attr_parsing/src/attributes/lint.rs b/compiler/rustc_attr_parsing/src/attributes/lint.rs
@@ -8,6 +8,7 @@ use thin_vec::ThinVec;
 
 use crate::attributes::{AcceptMapping, AttributeParser, AttributeStability};
 use crate::context::{AcceptContext, ExpectStringLiteral, FinalizeContext};
+use crate::diagnostics::BadAttributeLitHelp;
 use crate::parser::{ArgParser, MetaItemOrLitParser};
 use crate::target_checking::AllowedTargets;
 use crate::target_checking::Policy::{Allow, Warn};
@@ -36,9 +37,10 @@ impl LintParser {
                 let p = parsers.last()?.meta_item()?;
                 let nv = p.args().as_name_value()?;
                 if !p.path().word_is(sym::reason) {
-                    cx.emit_err(diagnostics::MalformedAttribute {
+                    cx.emit_err(diagnostics::ExpectedLint {
                         span: p.span(),
-                        kind: diagnostics::MalformedAttributeKind::BadAttributeArgument(p.span()),
+                        help: BadAttributeLitHelp::Other { kind: kind.sym() },
+                        kind: kind.sym(),
                     });
                 } else {
                     parsers = &parsers[..(parsers.len() - 1)];
@@ -90,17 +92,16 @@ impl LintParser {
                                 nv.expect_string_literal(cx);
                             }
                             ArgParser::NameValue(_) | ArgParser::List(_) => {
-                                cx.emit_err(diagnostics::MalformedAttribute {
+                                cx.emit_err(diagnostics::ExpectedLint {
                                     span: p.span(),
-                                    kind: diagnostics::MalformedAttributeKind::BadAttributeArgument(
-                                        item.span(),
-                                    ),
+                                    help: BadAttributeLitHelp::Other { kind: kind.sym() },
+                                    kind: kind.sym(),
                                 });
                             }
                         }
                     }
                     MetaItemOrLitParser::Lit(lit) => {
-                        cx.emit_err(diagnostics::BadAttributeLit {
+                        cx.emit_err(diagnostics::ExpectedLint {
                             span: item.span(),
                             help: if lit.kind.is_str() {
                                 diagnostics::BadAttributeLitHelp::StrLit {
@@ -110,6 +111,7 @@ impl LintParser {
                             } else {
                                 diagnostics::BadAttributeLitHelp::Other { kind: kind.sym() }
                             },
+                            kind: kind.sym(),
                         });
                     }
                 }

diff --git a/compiler/rustc_attr_parsing/src/diagnostics.rs b/compiler/rustc_attr_parsing/src/diagnostics.rs
@@ -2146,18 +2146,17 @@ pub(crate) struct MalformedAttribute {
 
 #[derive(Subdiagnostic)]
 pub(crate) enum MalformedAttributeKind {
-    #[label("bad attribute argument")]
-    BadAttributeArgument(#[primary_span] Span),
     #[label("reason in lint attribute must come last")]
     ReasonMustComeLast(#[primary_span] Span),
 }
 
 #[derive(Diagnostic)]
-#[diag("expected a lint, found literal")]
-pub(crate) struct BadAttributeLit {
+#[diag("malformed `{$kind}` attribute input")]
+pub(crate) struct ExpectedLint {
     #[primary_span]
     #[label("not the name of a lint")]
     pub span: Span,
+    pub kind: Symbol,
     #[subdiagnostic]
     pub help: BadAttributeLitHelp,
 }

diff --git a/compiler/rustc_error_codes/src/error_codes/E0452.md b/compiler/rustc_error_codes/src/error_codes/E0452.md
@@ -3,7 +3,7 @@ An invalid lint attribute has been given.
 Erroneous code example:
 
 ```compile_fail,E0452
-#![allow(foo = "")] // error: malformed lint attribute
+#![allow(reason = "", foo)] // error: malformed lint attribute
 ```
 
 Lint attributes only accept a list of identifiers (where each identifier is a

diff --git a/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs b/tests/ui/attributes/unsafe/proc-unsafe-attributes.rs
@@ -33,9 +33,9 @@ pub fn e() {}
 //~| ERROR: expected identifier, found keyword `unsafe`
 //~| ERROR: expected identifier, found keyword `unsafe`
 //~| ERROR: expected identifier, found keyword `unsafe`
-//~| ERROR: malformed lint attribute input
-//~| ERROR: malformed lint attribute input
-//~| ERROR: malformed lint attribute input
+//~| ERROR: malformed
+//~| ERROR: malformed
+//~| ERROR: malformed
 pub fn f() {}
 
 fn main() {}
diff --git a/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr b/tests/ui/attributes/unsafe/proc-unsafe-attributes.stderr
@@ -25,11 +25,13 @@ help: escape `unsafe` to use it as an identifier
 LL | #[unsafe(allow(r#unsafe(dead_code)))]
    |                ++
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/proc-unsafe-attributes.rs:29:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
-   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+   |                ^^^^^^^^^^^^^^^^^ not the name of a lint
+   |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
 
 error: the `proc_macro` attribute is only usable with crates of the `proc-macro` crate type
   --> $DIR/proc-unsafe-attributes.rs:1:10
@@ -85,12 +87,13 @@ help: escape `unsafe` to use it as an identifier
 LL | #[unsafe(allow(r#unsafe(dead_code)))]
    |                ++
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/proc-unsafe-attributes.rs:29:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
-   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+   |                ^^^^^^^^^^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `proc_macro` is not an unsafe attribute
@@ -176,15 +179,15 @@ help: escape `unsafe` to use it as an identifier
 LL | #[unsafe(allow(r#unsafe(dead_code)))]
    |                ++
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/proc-unsafe-attributes.rs:29:16
    |
 LL | #[unsafe(allow(unsafe(dead_code)))]
-   |                ^^^^^^^^^^^^^^^^^ bad attribute argument
+   |                ^^^^^^^^^^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 21 previous errors
 
-Some errors have detailed explanations: E0452, E0565.
-For more information about an error, try `rustc --explain E0452`.
+For more information about this error, try `rustc --explain E0565`.
diff --git a/tests/ui/diagnostic-flags/deduplicate-diagnostics.deduplicate.stderr b/tests/ui/diagnostic-flags/deduplicate-diagnostics.deduplicate.stderr
@@ -1,4 +1,4 @@
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/deduplicate-diagnostics.rs:10:8
    |
 LL | #[deny("literal")]

diff --git a/tests/ui/diagnostic-flags/deduplicate-diagnostics.duplicate.stderr b/tests/ui/diagnostic-flags/deduplicate-diagnostics.duplicate.stderr
@@ -1,4 +1,4 @@
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/deduplicate-diagnostics.rs:10:8
    |
 LL | #[deny("literal")]
@@ -20,7 +20,7 @@ LL | #[derive(Unresolved)]
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/deduplicate-diagnostics.rs:10:8
    |
 LL | #[deny("literal")]
@@ -29,7 +29,7 @@ LL | #[deny("literal")]
    = help: try using `#[deny(literal)]`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/deduplicate-diagnostics.rs:10:8
    |
 LL | #[deny("literal")]

diff --git a/tests/ui/diagnostic-flags/deduplicate-diagnostics.rs b/tests/ui/diagnostic-flags/deduplicate-diagnostics.rs
@@ -7,7 +7,7 @@
                       //[duplicate]~| ERROR cannot find derive macro `Unresolved` in this scope
 struct S;
 
-#[deny("literal")] //~ ERROR expected a lint, found literal
-                   //[duplicate]~| ERROR expected a lint, found literal
-                   //[duplicate]~| ERROR expected a lint, found literal
+#[deny("literal")] //~ ERROR malformed
+                   //[duplicate]~| ERROR malformed
+                   //[duplicate]~| ERROR malformed
 fn main() {}
diff --git a/tests/ui/error-codes/E0452.rs b/tests/ui/error-codes/E0452.rs
@@ -1,8 +1,8 @@
-#![allow(foo = "")] //~ ERROR E0452
-                    //~| ERROR E0452
-                    //~| ERROR E0452
-                    //~| ERROR E0452
-                    //~| ERROR E0452
-                    //~| ERROR E0452
+#![allow(foo = "")] //~ ERROR malformed
+                    //~| ERROR malformed
+                    //~| ERROR malformed
+                    //~| ERROR malformed
+                    //~| ERROR malformed
+                    //~| ERROR malformed
 fn main() {
 }
diff --git a/tests/ui/error-codes/E0452.stderr b/tests/ui/error-codes/E0452.stderr
@@ -1,49 +1,55 @@
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/E0452.rs:1:10
    |
 LL | #![allow(foo = "")]
-   |          ^^^^^^^^ bad attribute argument
+   |          ^^^^^^^^ not the name of a lint
+   |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/E0452.rs:1:10
    |
 LL | #![allow(foo = "")]
-   |          ^^^^^^^^ bad attribute argument
+   |          ^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/E0452.rs:1:10
    |
 LL | #![allow(foo = "")]
-   |          ^^^^^^^^ bad attribute argument
+   |          ^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/E0452.rs:1:10
    |
 LL | #![allow(foo = "")]
-   |          ^^^^^^^^ bad attribute argument
+   |          ^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/E0452.rs:1:10
    |
 LL | #![allow(foo = "")]
-   |          ^^^^^^^^ bad attribute argument
+   |          ^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error[E0452]: malformed lint attribute input
+error: malformed `allow` attribute input
   --> $DIR/E0452.rs:1:10
    |
 LL | #![allow(foo = "")]
-   |          ^^^^^^^^ bad attribute argument
+   |          ^^^^^^^^ not the name of a lint
    |
+   = help: for example, write `#[allow(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 6 previous errors
 
-For more information about this error, try `rustc --explain E0452`.
diff --git a/tests/ui/lint/lint-attribute-literals.rs b/tests/ui/lint/lint-attribute-literals.rs
@@ -1,11 +1,11 @@
 // Checks that lint attributes with literals have an explanatory error
 
 #[allow("literal")]
-//~^ ERROR expected a lint, found literal
-//~| ERROR expected a lint, found literal
-//~| ERROR expected a lint, found literal
+//~^ ERROR malformed
+//~| ERROR malformed
+//~| ERROR malformed
 #[deny(1.0)]
-//~^ ERROR expected a lint, found literal
-//~| ERROR expected a lint, found literal
-//~| ERROR expected a lint, found literal
+//~^ ERROR malformed
+//~| ERROR malformed
+//~| ERROR malformed
 fn main() {}
diff --git a/tests/ui/lint/lint-attribute-literals.stderr b/tests/ui/lint/lint-attribute-literals.stderr
@@ -1,20 +1,20 @@
-error: expected a lint, found literal
+error: malformed `allow` attribute input
   --> $DIR/lint-attribute-literals.rs:3:9
    |
 LL | #[allow("literal")]
    |         ^^^^^^^^^ not the name of a lint
    |
    = help: try using `#[allow(literal)]`
 
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/lint-attribute-literals.rs:7:8
    |
 LL | #[deny(1.0)]
    |        ^^^ not the name of a lint
    |
    = help: for example, write `#[deny(dead_code)]` for `dead_code`
 
-error: expected a lint, found literal
+error: malformed `allow` attribute input
   --> $DIR/lint-attribute-literals.rs:3:9
    |
 LL | #[allow("literal")]
@@ -23,7 +23,7 @@ LL | #[allow("literal")]
    = help: try using `#[allow(literal)]`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/lint-attribute-literals.rs:7:8
    |
 LL | #[deny(1.0)]
@@ -32,7 +32,7 @@ LL | #[deny(1.0)]
    = help: for example, write `#[deny(dead_code)]` for `dead_code`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: expected a lint, found literal
+error: malformed `allow` attribute input
   --> $DIR/lint-attribute-literals.rs:3:9
    |
 LL | #[allow("literal")]
@@ -41,7 +41,7 @@ LL | #[allow("literal")]
    = help: try using `#[allow(literal)]`
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: expected a lint, found literal
+error: malformed `deny` attribute input
   --> $DIR/lint-attribute-literals.rs:7:8
    |
 LL | #[deny(1.0)]

diff --git a/tests/ui/lint/lint-malformed.rs b/tests/ui/lint/lint-malformed.rs
@@ -1,8 +1,8 @@
 #![deny = "foo"] //~ ERROR malformed `deny` attribute input
-#![allow(bar = "baz")] //~ ERROR malformed lint attribute
-                       //~| ERROR malformed lint attribute
-                       //~| ERROR malformed lint attribute
-                       //~| ERROR malformed lint attribute
-                       //~| ERROR malformed lint attribute
-                       //~| ERROR malformed lint attribute
+#![allow(bar = "baz")] //~ ERROR malformed
+                       //~| ERROR malformed
+                       //~| ERROR malformed
+                       //~| ERROR malformed
+                       //~| ERROR malformed
+                       //~| ERROR malformed
 fn main() { }