Improve invalid cfg predicate error

compiler/rustc_attr_parsing/src/attributes/cfg.rs

@@ -103,10 +103,11 @@ pub fn parse_cfg_entry(
                 Some(sym::target) => parse_cfg_entry_target(cx, list, meta.span())?,
                 Some(sym::version) => parse_cfg_entry_version(cx, list, meta.span())?,
                 _ => {
-                    return Err(cx.emit_err(session_diagnostics::InvalidPredicate {
-                        span: meta.span(),
-                        predicate: meta.path().to_string(),
-                    }));
+                    let mut possibilities = vec![sym::any, sym::all, sym::not, sym::target];
+                    if cx.features().cfg_version() {
+                        possibilities.push(sym::version);
+                    }
+                    return Err(cx.adcx().expected_specific_argument(meta.span(), &possibilities));
                 }
             },
             a @ (ArgParser::NoArgs | ArgParser::NameValue(_)) => {

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -13,15 +13,6 @@ use rustc_target::spec::TargetTuple;
 use crate::AttributeTemplate;
 use crate::context::Suggestion;
 
-#[derive(Diagnostic)]
-#[diag("invalid predicate `{$predicate}`", code = E0537)]
-pub(crate) struct InvalidPredicate {
-    #[primary_span]
-    pub span: Span,
-
-    pub predicate: String,
-}
-
 #[derive(Diagnostic)]
 #[diag("{$attr_str} attribute cannot have empty value")]
 pub(crate) struct DocAliasEmpty<'a> {

compiler/rustc_error_codes/src/error_codes/E0537.md

@@ -1,8 +1,9 @@
+#### Note: this error code is no longer emitted by the compiler
 An unknown predicate was used inside the `cfg` attribute.
 
 Erroneous code example:
 
-```compile_fail,E0537
+```compile_fail,E0539
 #[cfg(unknown())] // error: invalid predicate `unknown`
 pub fn something() {}
 

tests/ui/attributes/unsafe/extraneous-unsafe-attributes.rs

@@ -29,5 +29,5 @@ static FOO: usize = 0;
 fn main() {
     let _a = cfg!(unsafe(foo));
     //~^ ERROR: expected identifier, found keyword `unsafe`
-    //~^^ ERROR: invalid predicate `r#unsafe`
+    //~^^ ERROR: malformed `cfg` macro input [E0539]
 }

tests/ui/attributes/unsafe/extraneous-unsafe-attributes.stderr

@@ -33,11 +33,20 @@ help: escape `unsafe` to use it as an identifier
 LL |     let _a = cfg!(r#unsafe(foo));
    |                   ++
 
-error[E0537]: invalid predicate `r#unsafe`
-  --> $DIR/extraneous-unsafe-attributes.rs:30:19
+error[E0539]: malformed `cfg` macro input
+  --> $DIR/extraneous-unsafe-attributes.rs:30:14
    |
 LL |     let _a = cfg!(unsafe(foo));
-   |                   ^^^^^^^^^^^
+   |              ^^^^^-----------^
+   |                   |
+   |                   valid arguments are `any`, `all`, `not` or `target`
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>
+help: must be of the form
+   |
+LL -     let _a = cfg!(unsafe(foo));
+LL +     let _a = cfg!(predicate);
+   |
 
 error: `ignore` is not an unsafe attribute
   --> $DIR/extraneous-unsafe-attributes.rs:12:3
@@ -81,4 +90,4 @@ LL | #[unsafe(used)]
 
 error: aborting due to 10 previous errors
 
-For more information about this error, try `rustc --explain E0537`.
+For more information about this error, try `rustc --explain E0539`.

tests/ui/conditional-compilation/cfg-attr-invalid-predicate.rs

@@ -1,4 +1,4 @@
-#[cfg(foo(bar))] //~ ERROR invalid predicate `foo`
+#[cfg(foo(bar))] //~ ERROR malformed `cfg` attribute input [E0539]
 fn check() {}
 
 fn main() {}

tests/ui/conditional-compilation/cfg-attr-invalid-predicate.stderr

@@ -1,9 +1,18 @@
-error[E0537]: invalid predicate `foo`
-  --> $DIR/cfg-attr-invalid-predicate.rs:1:7
+error[E0539]: malformed `cfg` attribute input
+  --> $DIR/cfg-attr-invalid-predicate.rs:1:1
    |
 LL | #[cfg(foo(bar))]
-   |       ^^^^^^^^
+   | ^^^^^^--------^^
+   |       |
+   |       valid arguments are `any`, `all`, `not` or `target`
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>
+help: must be of the form
+   |
+LL - #[cfg(foo(bar))]
+LL + #[cfg(predicate)]
+   |
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0537`.
+For more information about this error, try `rustc --explain E0539`.

tests/ui/conditional-compilation/cfg-attr-syntax-validation.rs

@@ -34,7 +34,9 @@ struct S5;
 //~| NOTE for more information, visit
 struct S6;
 
-#[cfg(a())] //~ ERROR invalid predicate `a`
+#[cfg(a())] //~ ERROR malformed `cfg` attribute input
+//~| NOTE valid arguments are `any`, `all`, `not` or `target`
+//~| NOTE for more information, visit
 struct S7;
 
 #[cfg(a = 10)] //~ ERROR malformed `cfg` attribute input

tests/ui/conditional-compilation/cfg-attr-syntax-validation.stderr

@@ -89,14 +89,23 @@ LL - #[cfg(a::b)]
 LL + #[cfg(predicate)]
    |
 
-error[E0537]: invalid predicate `a`
-  --> $DIR/cfg-attr-syntax-validation.rs:37:7
+error[E0539]: malformed `cfg` attribute input
+  --> $DIR/cfg-attr-syntax-validation.rs:37:1
    |
 LL | #[cfg(a())]
-   |       ^^^
+   | ^^^^^^---^^
+   |       |
+   |       valid arguments are `any`, `all`, `not` or `target`
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute>
+help: must be of the form
+   |
+LL - #[cfg(a())]
+LL + #[cfg(predicate)]
+   |
 
 error[E0539]: malformed `cfg` attribute input
-  --> $DIR/cfg-attr-syntax-validation.rs:40:1
+  --> $DIR/cfg-attr-syntax-validation.rs:42:1
    |
 LL | #[cfg(a = 10)]
    | ^^^^^^^^^^--^^
@@ -111,7 +120,7 @@ LL + #[cfg(predicate)]
    |
 
 error[E0539]: malformed `cfg` attribute input
-  --> $DIR/cfg-attr-syntax-validation.rs:45:1
+  --> $DIR/cfg-attr-syntax-validation.rs:47:1
    |
 LL | #[cfg(a = b"hi")]
    | ^^^^^^^^^^-^^^^^^
@@ -121,7 +130,7 @@ LL | #[cfg(a = b"hi")]
    = note: expected a normal string literal, not a byte string literal
 
 error: expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found `expr` metavariable
-  --> $DIR/cfg-attr-syntax-validation.rs:51:25
+  --> $DIR/cfg-attr-syntax-validation.rs:53:25
    |
 LL |         #[cfg(feature = $expr)]
    |                         ^^^^^
@@ -133,5 +142,5 @@ LL | generate_s10!(concat!("nonexistent"));
 
 error: aborting due to 10 previous errors
 
-Some errors have detailed explanations: E0537, E0539, E0565, E0805.
-For more information about an error, try `rustc --explain E0537`.
+Some errors have detailed explanations: E0539, E0565, E0805.
+For more information about an error, try `rustc --explain E0539`.

tests/ui/conditional-compilation/cfg_attr-attr-syntax-validation.rs

@@ -16,7 +16,7 @@ struct S5;
 #[cfg_attr(a::b)] //~ ERROR malformed `cfg_attr` attribute input
 struct S6;
 
-#[cfg_attr(a())] //~ ERROR invalid predicate `a`
+#[cfg_attr(a())] //~ ERROR malformed `cfg_attr` attribute input [E0539]
 struct S7;
 
 #[cfg_attr(a = 10)] //~ ERROR malformed `cfg_attr` attribute input

tests/ui/conditional-compilation/cfg_attr-attr-syntax-validation.stderr

@@ -67,11 +67,20 @@ LL - #[cfg_attr(a::b)]
 LL + #[cfg_attr(predicate, attr1, attr2, ...)]
    |
 
-error[E0537]: invalid predicate `a`
-  --> $DIR/cfg_attr-attr-syntax-validation.rs:19:12
+error[E0539]: malformed `cfg_attr` attribute input
+  --> $DIR/cfg_attr-attr-syntax-validation.rs:19:1
    |
 LL | #[cfg_attr(a())]
-   |            ^^^
+   | ^^^^^^^^^^^---^^
+   |            |
+   |            valid arguments are `any`, `all`, `not` or `target`
+   |
+   = note: for more information, visit <https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute>
+help: must be of the form
+   |
+LL - #[cfg_attr(a())]
+LL + #[cfg_attr(predicate, attr1, attr2, ...)]
+   |
 
 error[E0539]: malformed `cfg_attr` attribute input
   --> $DIR/cfg_attr-attr-syntax-validation.rs:22:1
@@ -177,5 +186,5 @@ LL | #[cfg_attr(true, link_section)]
 
 error: aborting due to 13 previous errors; 1 warning emitted
 
-Some errors have detailed explanations: E0537, E0539, E0565, E0805.
-For more information about an error, try `rustc --explain E0537`.
+Some errors have detailed explanations: E0539, E0565, E0805.
+For more information about an error, try `rustc --explain E0539`.

tests/ui/macros/cfg_select.rs

@@ -188,7 +188,7 @@ cfg_select! {
 
 cfg_select! {
     a() => {}
-    //~^ ERROR invalid predicate `a` [E0537]
+    //~^ ERROR malformed `cfg_select` macro input [E0539]
 }
 
 cfg_select! {

tests/ui/macros/cfg_select.stderr

@@ -37,11 +37,11 @@ error[E0565]: malformed `cfg_select` macro input
 LL |     a::b => {}
    |     ^^^^ expected a valid identifier here
 
-error[E0537]: invalid predicate `a`
+error[E0539]: malformed `cfg_select` macro input
   --> $DIR/cfg_select.rs:190:5
    |
 LL |     a() => {}
-   |     ^^^
+   |     ^^^ valid arguments are `any`, `all`, `not` or `target`
 
 error: expected one of `(`, `::`, `=>`, or `=`, found `+`
   --> $DIR/cfg_select.rs:195:7
@@ -185,5 +185,5 @@ LL |     cfg!() => {}
 
 error: aborting due to 17 previous errors; 7 warnings emitted
 
-Some errors have detailed explanations: E0537, E0565, E0753.
-For more information about an error, try `rustc --explain E0537`.
+Some errors have detailed explanations: E0539, E0565, E0753.
+For more information about an error, try `rustc --explain E0539`.