special case expected_single_argument when no argument is provided

scrabsha · scrabsha · commit 362e0f9160c8 · 2026-04-09T16:39:58.000Z
diff --git a/compiler/rustc_attr_parsing/src/attributes/cfg.rs b/compiler/rustc_attr_parsing/src/attributes/cfg.rs
@@ -78,7 +78,7 @@ pub fn parse_cfg<S: Stage>(
             }
         }
 
-        adcx.expected_single_argument(list.span);
+        adcx.expected_single_argument(list.span, list.len());
         return None;
     };
     parse_cfg_entry(cx, single).ok()
@@ -93,7 +93,7 @@ pub fn parse_cfg_entry<S: Stage>(
             ArgParser::List(list) => match meta.path().word_sym() {
                 Some(sym::not) => {
                     let Some(single) = list.single() else {
-                        return Err(cx.adcx().expected_single_argument(list.span));
+                        return Err(cx.adcx().expected_single_argument(list.span, list.len()));
                     };
                     CfgEntry::Not(Box::new(parse_cfg_entry(cx, single)?), list.span)
                 }
diff --git a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
@@ -30,7 +30,7 @@ impl<S: Stage> SingleAttributeParser<S> for OptimizeParser {
         };
 
         let Some(single) = list.single() else {
-            cx.adcx().expected_single_argument(list.span);
+            cx.adcx().expected_single_argument(list.span, list.len());
             return None;
         };
 
@@ -91,7 +91,7 @@ impl<S: Stage> SingleAttributeParser<S> for CoverageParser {
         };
 
         let Some(arg) = args.single() else {
-            cx.adcx().expected_single_argument(args.span);
+            cx.adcx().expected_single_argument(args.span, args.len());
             return None;
         };
 
@@ -394,7 +394,7 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
                 ArgParser::NoArgs => UsedBy::Default,
                 ArgParser::List(list) => {
                     let Some(l) = list.single() else {
-                        cx.adcx().expected_single_argument(list.span);
+                        cx.adcx().expected_single_argument(list.span, list.len());
                         return;
                     };
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/debugger.rs b/compiler/rustc_attr_parsing/src/attributes/debugger.rs
@@ -26,7 +26,7 @@ impl<S: Stage> CombineAttributeParser<S> for DebuggerViualizerParser {
             return None;
         };
         let Some(single) = l.single() else {
-            cx.adcx().expected_single_argument(l.span);
+            cx.adcx().expected_single_argument(l.span, l.len());
             return None;
         };
         let Some(mi) = single.meta_item() else {
diff --git a/compiler/rustc_attr_parsing/src/attributes/inline.rs b/compiler/rustc_attr_parsing/src/attributes/inline.rs
@@ -38,7 +38,7 @@ impl<S: Stage> SingleAttributeParser<S> for InlineParser {
             ArgParser::NoArgs => Some(AttributeKind::Inline(InlineAttr::Hint, cx.attr_span)),
             ArgParser::List(list) => {
                 let Some(l) = list.single() else {
-                    cx.adcx().expected_single_argument(list.span);
+                    cx.adcx().expected_single_argument(list.span, list.len());
                     return None;
                 };
 
@@ -80,7 +80,7 @@ impl<S: Stage> SingleAttributeParser<S> for RustcForceInlineParser {
             ArgParser::NoArgs => None,
             ArgParser::List(list) => {
                 let Some(l) = list.single() else {
-                    cx.adcx().expected_single_argument(list.span);
+                    cx.adcx().expected_single_argument(list.span, list.len());
                     return None;
                 };
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
@@ -393,7 +393,7 @@ impl LinkParser {
             return true;
         };
         let Some(link_cfg) = link_cfg.single() else {
-            cx.adcx().expected_single_argument(item.span());
+            cx.adcx().expected_single_argument(item.span(), link_cfg.len());
             return true;
         };
         if !features.link_cfg() {
diff --git a/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/macro_attrs.rs
@@ -181,7 +181,7 @@ impl<S: Stage> SingleAttributeParser<S> for CollapseDebugInfoParser {
             return None;
         };
         let Some(single) = list.single() else {
-            cx.adcx().expected_single_argument(list.span);
+            cx.adcx().expected_single_argument(list.span, list.len());
             return None;
         };
         let Some(mi) = single.meta_item() else {
diff --git a/compiler/rustc_attr_parsing/src/attributes/prototype.rs b/compiler/rustc_attr_parsing/src/attributes/prototype.rs
@@ -82,7 +82,7 @@ fn extract_value<S: Stage>(
     }
 
     let Some(val) = arg.name_value() else {
-        cx.adcx().expected_single_argument(arg.span().unwrap_or(span));
+        cx.adcx().expected_single_argument(arg.span().unwrap_or(span), 2);
         *failed = true;
         return;
     };
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -297,7 +297,7 @@ impl RustcAlignParser {
             }
             ArgParser::List(list) => {
                 let Some(align) = list.single() else {
-                    cx.adcx().expected_single_argument(list.span);
+                    cx.adcx().expected_single_argument(list.span, list.len());
                     return;
                 };
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
@@ -197,7 +197,7 @@ impl<S: Stage> SingleAttributeParser<S> for RustcLintOptDenyFieldAccessParser {
     fn convert(cx: &mut AcceptContext<'_, '_, S>, args: &ArgParser) -> Option<AttributeKind> {
         let Some(arg) = args.list().and_then(MetaItemListParser::single) else {
             let attr_span = cx.attr_span;
-            cx.adcx().expected_single_argument(attr_span);
+            cx.adcx().expected_single_argument(attr_span, 2);
             return None;
         };
 
@@ -382,7 +382,7 @@ impl<S: Stage> SingleAttributeParser<S> for RustcDeprecatedSafe2024Parser {
         };
 
         let Some(single) = args.single() else {
-            cx.adcx().expected_single_argument(args.span);
+            cx.adcx().expected_single_argument(args.span, args.len());
             return None;
         };
 
@@ -1022,7 +1022,7 @@ impl<S: Stage> SingleAttributeParser<S> for RustcIfThisChangedParser {
             ArgParser::List(list) => {
                 let Some(item) = list.single() else {
                     let attr_span = cx.attr_span;
-                    cx.adcx().expected_single_argument(attr_span);
+                    cx.adcx().expected_single_argument(attr_span, list.len());
                     return None;
                 };
                 let Some(ident) = item.meta_item().and_then(|item| item.ident()) else {
@@ -1084,7 +1084,7 @@ impl<S: Stage> CombineAttributeParser<S> for RustcThenThisWouldNeedParser {
         }
         let Some(item) = args.list().and_then(|l| l.single()) else {
             let inner_span = cx.inner_span;
-            cx.adcx().expected_single_argument(inner_span);
+            cx.adcx().expected_single_argument(inner_span, 2);
             return None;
         };
         let Some(ident) = item.meta_item().and_then(|item| item.ident()) else {
diff --git a/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/test_attrs.rs
@@ -72,7 +72,7 @@ impl<S: Stage> SingleAttributeParser<S> for ShouldPanicParser {
                 }
                 ArgParser::List(list) => {
                     let Some(single) = list.single() else {
-                        cx.adcx().expected_single_argument(list.span);
+                        cx.adcx().expected_single_argument(list.span, list.len());
                         return None;
                     };
                     let Some(single) = single.meta_item() else {
@@ -150,7 +150,7 @@ impl<S: Stage> SingleAttributeParser<S> for RustcAbiParser {
 
         let Some(arg) = args.single() else {
             let attr_span = cx.attr_span;
-            cx.adcx().expected_single_argument(attr_span);
+            cx.adcx().expected_single_argument(attr_span, args.len());
             return None;
         };
 
@@ -215,7 +215,7 @@ impl<S: Stage> SingleAttributeParser<S> for TestRunnerParser {
         };
 
         let Some(single) = list.single() else {
-            cx.adcx().expected_single_argument(list.span);
+            cx.adcx().expected_single_argument(list.span, list.len());
             return None;
         };
 
diff --git a/compiler/rustc_attr_parsing/src/attributes/util.rs b/compiler/rustc_attr_parsing/src/attributes/util.rs
@@ -47,7 +47,7 @@ pub(crate) fn parse_single_integer<S: Stage>(
         return None;
     };
     let Some(single) = list.single() else {
-        cx.adcx().expected_single_argument(list.span);
+        cx.adcx().expected_single_argument(list.span, list.len());
         return None;
     };
     let Some(lit) = single.lit() else {
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
@@ -751,8 +751,22 @@ where
         self.emit_parse_error(span, AttributeParseErrorReason::ExpectedNotLiteral)
     }
 
-    pub(crate) fn expected_single_argument(&mut self, span: Span) -> ErrorGuaranteed {
-        self.emit_parse_error(span, AttributeParseErrorReason::ExpectedSingleArgument)
+    /// Signals that we expected exactly one argument and that we got either zero or two or more.
+    /// The `provided_arguments` argument allows distinguishing between "expected an argument here"
+    /// (when zero arguments are provided) and "expect a single argument here" (when two or more
+    /// arguments are provided).
+    pub(crate) fn expected_single_argument(
+        &mut self,
+        span: Span,
+        provided_arguments: usize,
+    ) -> ErrorGuaranteed {
+        let reason = if provided_arguments == 0 {
+            AttributeParseErrorReason::ExpectedArgument
+        } else {
+            AttributeParseErrorReason::ExpectedSingleArgument
+        };
+
+        self.emit_parse_error(span, reason)
     }
 
     pub(crate) fn expected_at_least_one_argument(&mut self, span: Span) -> ErrorGuaranteed {
diff --git a/compiler/rustc_attr_parsing/src/session_diagnostics.rs b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
@@ -557,6 +557,7 @@ pub(crate) enum AttributeParseErrorReason<'a> {
         upper_bound: isize,
     },
     ExpectedAtLeastOneArgument,
+    ExpectedArgument,
     ExpectedSingleArgument,
     ExpectedList,
     ExpectedListOrNoArgs,
@@ -777,6 +778,10 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError<'_> {
                 diag.span_label(self.span, "expected a single argument here");
                 diag.code(E0805);
             }
+            AttributeParseErrorReason::ExpectedArgument => {
+                diag.span_label(self.span, "expected an argument here");
+                diag.code(E0805);
+            }
             AttributeParseErrorReason::ExpectedAtLeastOneArgument => {
                 diag.span_label(self.span, "expected at least 1 argument here");
             }
diff --git a/tests/rustdoc-ui/doc-cfg.stderr b/tests/rustdoc-ui/doc-cfg.stderr
@@ -4,7 +4,7 @@ error[E0805]: malformed `doc` attribute input
 LL | #[doc(cfg(), cfg(foo, bar))]
    | ^^^^^^^^^--^^^^^^^^^^^^^^^^^
    |          |
-   |          expected a single argument here
+   |          expected an argument here
    |
 help: if the function should be disabled, use `#[cfg(false)]`
    |
@@ -36,7 +36,7 @@ error[E0805]: malformed `doc` attribute input
 LL | #[doc(cfg())]
    | ^^^^^^^^^--^^
    |          |
-   |          expected a single argument here
+   |          expected an argument here
    |
 help: if the function should be disabled, use `#[cfg(false)]`
    |
diff --git a/tests/ui/attributes/inline/invalid-inline.stderr b/tests/ui/attributes/inline/invalid-inline.stderr
@@ -25,7 +25,7 @@ error[E0805]: malformed `inline` attribute input
 LL | #[inline()]
    | ^^^^^^^^--^
    |         |
-   |         expected a single argument here
+   |         expected an argument here
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute>
 help: try changing it to one of the following valid forms of the attribute
diff --git a/tests/ui/attributes/malformed-attrs.stderr b/tests/ui/attributes/malformed-attrs.stderr
@@ -242,7 +242,7 @@ error[E0805]: malformed `used` attribute input
 LL | #[used()]
    | ^^^^^^--^
    |       |
-   |       expected a single argument here
+   |       expected an argument here
    |
 help: try changing it to one of the following valid forms of the attribute
    |
diff --git a/tests/ui/cfg/suggest-any-or-all.stderr b/tests/ui/cfg/suggest-any-or-all.stderr
@@ -24,7 +24,7 @@ error[E0805]: malformed `cfg` attribute input
 LL | #[cfg()]
    | ^^^^^--^
    |      |
-   |      expected a single argument here
+   |      expected an argument here
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>
 help: if the struct should be disabled, use `#[cfg(false)]`
diff --git a/tests/ui/conditional-compilation/cfg-attr-syntax-validation.rs b/tests/ui/conditional-compilation/cfg-attr-syntax-validation.rs
@@ -12,7 +12,7 @@ struct S2;
 
 #[cfg()]
 //~^ ERROR malformed `cfg` attribute
-//~| NOTE expected a single argument here
+//~| NOTE expected an argument here
 //~| NOTE for more information, visit
 struct S3;
 
diff --git a/tests/ui/conditional-compilation/cfg-attr-syntax-validation.stderr b/tests/ui/conditional-compilation/cfg-attr-syntax-validation.stderr
@@ -26,7 +26,7 @@ error[E0805]: malformed `cfg` attribute input
 LL | #[cfg()]
    | ^^^^^--^
    |      |
-   |      expected a single argument here
+   |      expected an argument here
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>
 help: if the struct should be disabled, use `#[cfg(false)]`
diff --git a/tests/ui/conditional-compilation/cfg_attr-attr-syntax-validation.stderr b/tests/ui/conditional-compilation/cfg_attr-attr-syntax-validation.stderr
@@ -123,7 +123,7 @@ error[E0805]: malformed `inline` attribute input
 LL | #[cfg_attr(true, inline())]
    |                  ^^^^^^--
    |                        |
-   |                        expected a single argument here
+   |                        expected an argument here
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute>
 help: try changing it to one of the following valid forms of the attribute
diff --git a/tests/ui/coverage-attr/bad-syntax.stderr b/tests/ui/coverage-attr/bad-syntax.stderr
@@ -56,7 +56,7 @@ error[E0805]: malformed `coverage` attribute input
 LL | #[coverage()]
    | ^^^^^^^^^^--^
    |           |
-   |           expected a single argument here
+   |           expected an argument here
    |
 help: try changing it to one of the following valid forms of the attribute
    |
diff --git a/tests/ui/error-codes/E0540.stderr b/tests/ui/error-codes/E0540.stderr
@@ -4,7 +4,7 @@ error[E0805]: malformed `inline` attribute input
 LL | #[inline()]
    | ^^^^^^^^--^
    |         |
-   |         expected a single argument here
+   |         expected an argument here
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute>
 help: try changing it to one of the following valid forms of the attribute
diff --git a/tests/ui/link-native-libs/issue-43926.stderr b/tests/ui/link-native-libs/issue-43926.stderr
@@ -4,7 +4,7 @@ error[E0805]: malformed `link` attribute input
 LL | #[link(name = "foo", cfg())]
    | ^^^^^^^^^^^^^^^^^^^^^-----^^
    |                      |
-   |                      expected a single argument here
+   |                      expected an argument here
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/items/external-blocks.html#the-link-attribute>
 
diff --git a/tests/ui/linkage-attr/raw-dylib/windows/link-ordinal-missing-argument.rs b/tests/ui/linkage-attr/raw-dylib/windows/link-ordinal-missing-argument.rs
@@ -2,12 +2,12 @@
 extern "C" {
     #[link_ordinal()]
     //~^ ERROR malformed `link_ordinal` attribute input
-    //~| NOTE  expected a single argument
+    //~| NOTE expected an argument here
     //~| NOTE for more information, visit
     fn foo();
     #[link_ordinal()]
     //~^ ERROR malformed `link_ordinal` attribute input
-    //~| NOTE  expected a single argument
+    //~| NOTE expected an argument here
     //~| NOTE for more information, visit
     static mut imported_variable: i32;
 }
diff --git a/tests/ui/linkage-attr/raw-dylib/windows/link-ordinal-missing-argument.stderr b/tests/ui/linkage-attr/raw-dylib/windows/link-ordinal-missing-argument.stderr
@@ -4,7 +4,7 @@ error[E0805]: malformed `link_ordinal` attribute input
 LL |     #[link_ordinal()]
    |     ^^^^^^^^^^^^^^--^
    |     |             |
-   |     |             expected a single argument here
+   |     |             expected an argument here
    |     help: must be of the form: `#[link_ordinal(ordinal)]`
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/items/external-blocks.html#the-link_ordinal-attribute>
@@ -15,7 +15,7 @@ error[E0805]: malformed `link_ordinal` attribute input
 LL |     #[link_ordinal()]
    |     ^^^^^^^^^^^^^^--^
    |     |             |
-   |     |             expected a single argument here
+   |     |             expected an argument here
    |     help: must be of the form: `#[link_ordinal(ordinal)]`
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/items/external-blocks.html#the-link_ordinal-attribute>
diff --git a/tests/ui/span/E0805.stderr b/tests/ui/span/E0805.stderr
@@ -4,7 +4,7 @@ error[E0805]: malformed `cfg` macro input
 LL |     if cfg!(not()) { }
    |        ^^^^^^^^--^
    |        |       |
-   |        |       expected a single argument here
+   |        |       expected an argument here
    |        help: must be of the form: `cfg!(predicate)`
    |
    = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>

Original file line number	Diff line number	Diff line change
`@@ -78,7 +78,7 @@ pub fn parse_cfg<S: Stage>(`
`78`	`78`	`}`
`79`	`79`	`}`
`80`	`80`
`81`		`- adcx.expected_single_argument(list.span);`
	`81`	`+ adcx.expected_single_argument(list.span, list.len());`
`82`	`82`	`return None;`
`83`	`83`	`};`
`84`	`84`	`parse_cfg_entry(cx, single).ok()`
`@@ -93,7 +93,7 @@ pub fn parse_cfg_entry<S: Stage>(`
`93`	`93`	`ArgParser::List(list) => match meta.path().word_sym() {`
`94`	`94`	`Some(sym::not) => {`
`95`	`95`	`let Some(single) = list.single() else {`
`96`		`- return Err(cx.adcx().expected_single_argument(list.span));`
	`96`	`+ return Err(cx.adcx().expected_single_argument(list.span, list.len()));`
`97`	`97`	`};`
`98`	`98`	`CfgEntry::Not(Box::new(parse_cfg_entry(cx, single)?), list.span)`
`99`	`99`	`}`
Original file line number	Diff line number	Diff line change
`@@ -82,7 +82,7 @@ fn extract_value<S: Stage>(`
`82`	`82`	`}`
`83`	`83`
`84`	`84`	`let Some(val) = arg.name_value() else {`
`85`		`- cx.adcx().expected_single_argument(arg.span().unwrap_or(span));`
	`85`	`+ cx.adcx().expected_single_argument(arg.span().unwrap_or(span), 2);`
`86`	`86`	`*failed = true;`
`87`	`87`	`return;`
`88`	`88`	`};`
Original file line number	Diff line number	Diff line change
`@@ -297,7 +297,7 @@ impl RustcAlignParser {`
`297`	`297`	`}`
`298`	`298`	`ArgParser::List(list) => {`
`299`	`299`	`let Some(align) = list.single() else {`
`300`		`- cx.adcx().expected_single_argument(list.span);`
	`300`	`+ cx.adcx().expected_single_argument(list.span, list.len());`
`301`	`301`	`return;`
`302`	`302`	`};`
`303`	`303`