Improve check-cfg CLI errors with more structured diagnostics

Cargo.lock

@@ -4162,6 +4162,7 @@ dependencies = [
  "rustc_ast",
  "rustc_ast_lowering",
  "rustc_ast_passes",
+ "rustc_ast_pretty",
  "rustc_attr",
  "rustc_borrowck",
  "rustc_builtin_macros",

compiler/rustc_ast/src/token.rs

@@ -167,7 +167,7 @@ impl LitKind {
 
     pub fn descr(self) -> &'static str {
         match self {
-            Bool => panic!("literal token contains `Lit::Bool`"),
+            Bool => "boolean",
             Byte => "byte",
             Char => "char",
             Integer => "integer",

compiler/rustc_interface/Cargo.toml

@@ -10,6 +10,7 @@ rustc-rayon-core = { version = "0.5.0", optional = true }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_lowering = { path = "../rustc_ast_lowering" }
 rustc_ast_passes = { path = "../rustc_ast_passes" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_attr = { path = "../rustc_attr" }
 rustc_borrowck = { path = "../rustc_borrowck" }
 rustc_builtin_macros = { path = "../rustc_builtin_macros" }

compiler/rustc_interface/src/interface.rs

@@ -120,14 +120,45 @@ pub(crate) fn parse_check_cfg(dcx: &DiagCtxt, specs: Vec<String>) -> CheckCfg {
         );
         let filename = FileName::cfg_spec_source_code(&s);
 
+        const VISIT: &str =
+            "visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details";
+
         macro_rules! error {
             ($reason:expr) => {
                 #[allow(rustc::untranslatable_diagnostic)]
                 #[allow(rustc::diagnostic_outside_of_impl)]
-                dcx.fatal(format!(
-                    concat!("invalid `--check-cfg` argument: `{}` (", $reason, ")"),
-                    s
-                ))
+                {
+                    let mut diag =
+                        dcx.struct_fatal(format!("invalid `--check-cfg` argument: `{s}`"));
+                    diag.note($reason);
+                    diag.note(VISIT);
+                    diag.emit()
+                }
+            };
+            (in $arg:expr, $reason:expr) => {
+                #[allow(rustc::untranslatable_diagnostic)]
+                #[allow(rustc::diagnostic_outside_of_impl)]
+                {
+                    let mut diag =
+                        dcx.struct_fatal(format!("invalid `--check-cfg` argument: `{s}`"));
+
+                    let pparg = rustc_ast_pretty::pprust::meta_list_item_to_string($arg);
+                    if let Some(lit) = $arg.lit() {
+                        let (lit_kind_article, lit_kind_descr) = {
+                            let lit_kind = lit.as_token_lit().kind;
+                            (lit_kind.article(), lit_kind.descr())
+                        };
+                        diag.note(format!(
+                            "`{pparg}` is {lit_kind_article} {lit_kind_descr} literal"
+                        ));
+                    } else {
+                        diag.note(format!("`{pparg}` is invalid"));
+                    }
+
+                    diag.note($reason);
+                    diag.note(VISIT);
+                    diag.emit()
+                }
             };
         }
 
@@ -183,7 +214,7 @@ pub(crate) fn parse_check_cfg(dcx: &DiagCtxt, specs: Vec<String>) -> CheckCfg {
                 }
                 any_specified = true;
                 if !args.is_empty() {
-                    error!("`any()` must be empty");
+                    error!(in arg, "`any()` takes no argument");
                 }
             } else if arg.has_name(sym::values)
                 && let Some(args) = arg.meta_item_list()
@@ -202,25 +233,25 @@ pub(crate) fn parse_check_cfg(dcx: &DiagCtxt, specs: Vec<String>) -> CheckCfg {
                         && let Some(args) = arg.meta_item_list()
                     {
                         if values_any_specified {
-                            error!("`any()` in `values()` cannot be specified multiple times");
+                            error!(in arg, "`any()` in `values()` cannot be specified multiple times");
                         }
                         values_any_specified = true;
                         if !args.is_empty() {
-                            error!("`any()` must be empty");
+                            error!(in arg, "`any()` in `values()` takes no argument");
                         }
                     } else if arg.has_name(sym::none)
                         && let Some(args) = arg.meta_item_list()
                     {
                         values.insert(None);
                         if !args.is_empty() {
-                            error!("`none()` must be empty");
+                            error!(in arg, "`none()` in `values()` takes no argument");
                         }
                     } else {
-                        error!("`values()` arguments must be string literals, `none()` or `any()`");
+                        error!(in arg, "`values()` arguments must be string literals, `none()` or `any()`");
                     }
                 }
             } else {
-                error!("`cfg()` arguments must be simple identifiers, `any()` or `values(...)`");
+                error!(in arg, "`cfg()` arguments must be simple identifiers, `any()` or `values(...)`");
             }
         }
 

tests/ui/check-cfg/invalid-arguments.any_values.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(any(),values())` (`values()` cannot be specified before the names)
+error: invalid `--check-cfg` argument: `cfg(any(),values())`
+   |
+   = note: `values()` cannot be specified before the names
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.anything_else.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `anything_else(...)` (expected `cfg(name, values("value1", "value2", ... "valueN"))`)
+error: invalid `--check-cfg` argument: `anything_else(...)`
+   |
+   = note: expected `cfg(name, values("value1", "value2", ... "valueN"))`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.boolean.stderr

@@ -0,0 +1,6 @@
+error: invalid `--check-cfg` argument: `cfg(true)`
+   |
+   = note: `true` is a boolean literal
+   = note: `cfg()` arguments must be simple identifiers, `any()` or `values(...)`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
+

tests/ui/check-cfg/invalid-arguments.cfg_none.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(none())` (`cfg()` arguments must be simple identifiers, `any()` or `values(...)`)
+error: invalid `--check-cfg` argument: `cfg(none())`
+   |
+   = note: `none()` is invalid
+   = note: `cfg()` arguments must be simple identifiers, `any()` or `values(...)`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.giberich.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(...)` (expected `cfg(name, values("value1", "value2", ... "valueN"))`)
+error: invalid `--check-cfg` argument: `cfg(...)`
+   |
+   = note: expected `cfg(name, values("value1", "value2", ... "valueN"))`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.ident_in_values_1.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values(bar))` (`values()` arguments must be string literals, `none()` or `any()`)
+error: invalid `--check-cfg` argument: `cfg(foo,values(bar))`
+   |
+   = note: `bar` is invalid
+   = note: `values()` arguments must be string literals, `none()` or `any()`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.ident_in_values_2.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values("bar",bar,"bar"))` (`values()` arguments must be string literals, `none()` or `any()`)
+error: invalid `--check-cfg` argument: `cfg(foo,values("bar",bar,"bar"))`
+   |
+   = note: `bar` is invalid
+   = note: `values()` arguments must be string literals, `none()` or `any()`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.mixed_any.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(any(),values(any()))` (`values()` cannot be specified before the names)
+error: invalid `--check-cfg` argument: `cfg(any(),values(any()))`
+   |
+   = note: `values()` cannot be specified before the names
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.mixed_values_any.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values("bar",any()))` (`values()` arguments cannot specify string literals and `any()` at the same time)
+error: invalid `--check-cfg` argument: `cfg(foo,values("bar",any()))`
+   |
+   = note: `values()` arguments cannot specify string literals and `any()` at the same time
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.multiple_any.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(any(),any())` (`any()` cannot be specified multiple times)
+error: invalid `--check-cfg` argument: `cfg(any(),any())`
+   |
+   = note: `any()` cannot be specified multiple times
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.multiple_values.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values(),values())` (`values()` cannot be specified multiple times)
+error: invalid `--check-cfg` argument: `cfg(foo,values(),values())`
+   |
+   = note: `values()` cannot be specified multiple times
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.multiple_values_any.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values(any(),any()))` (`any()` in `values()` cannot be specified multiple times)
+error: invalid `--check-cfg` argument: `cfg(foo,values(any(),any()))`
+   |
+   = note: `any()` is invalid
+   = note: `any()` in `values()` cannot be specified multiple times
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.none_not_empty.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values(none("test")))` (`none()` must be empty)
+error: invalid `--check-cfg` argument: `cfg(foo,values(none("test")))`
+   |
+   = note: `none("test")` is invalid
+   = note: `none()` in `values()` takes no argument
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.not_empty_any.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(any(foo))` (`any()` must be empty)
+error: invalid `--check-cfg` argument: `cfg(any(foo))`
+   |
+   = note: `any(foo)` is invalid
+   = note: `any()` takes no argument
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.not_empty_values_any.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values(any(bar)))` (`any()` must be empty)
+error: invalid `--check-cfg` argument: `cfg(foo,values(any(bar)))`
+   |
+   = note: `any(bar)` is invalid
+   = note: `any()` in `values()` takes no argument
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.rs

@@ -2,7 +2,7 @@
 //
 //@ check-fail
 //@ no-auto-check-cfg
-//@ revisions: anything_else
+//@ revisions: anything_else boolean
 //@ revisions: string_for_name_1 string_for_name_2 multiple_any multiple_values
 //@ revisions: multiple_values_any not_empty_any not_empty_values_any
 //@ revisions: values_any_missing_values values_any_before_ident ident_in_values_1
@@ -11,6 +11,7 @@
 //@ revisions: none_not_empty cfg_none
 //
 //@ [anything_else]compile-flags: --check-cfg=anything_else(...)
+//@ [boolean]compile-flags: --check-cfg=cfg(true)
 //@ [string_for_name_1]compile-flags: --check-cfg=cfg("NOT_IDENT")
 //@ [string_for_name_2]compile-flags: --check-cfg=cfg(foo,"NOT_IDENT",bar)
 //@ [multiple_any]compile-flags: --check-cfg=cfg(any(),any())

tests/ui/check-cfg/invalid-arguments.string_for_name_1.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg("NOT_IDENT")` (`cfg()` arguments must be simple identifiers, `any()` or `values(...)`)
+error: invalid `--check-cfg` argument: `cfg("NOT_IDENT")`
+   |
+   = note: `"NOT_IDENT"` is a string literal
+   = note: `cfg()` arguments must be simple identifiers, `any()` or `values(...)`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.string_for_name_2.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,"NOT_IDENT",bar)` (`cfg()` arguments must be simple identifiers, `any()` or `values(...)`)
+error: invalid `--check-cfg` argument: `cfg(foo,"NOT_IDENT",bar)`
+   |
+   = note: `"NOT_IDENT"` is a string literal
+   = note: `cfg()` arguments must be simple identifiers, `any()` or `values(...)`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.unknown_meta_item_1.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `abc()` (expected `cfg(name, values("value1", "value2", ... "valueN"))`)
+error: invalid `--check-cfg` argument: `abc()`
+   |
+   = note: expected `cfg(name, values("value1", "value2", ... "valueN"))`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.unknown_meta_item_2.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,test())` (`cfg()` arguments must be simple identifiers, `any()` or `values(...)`)
+error: invalid `--check-cfg` argument: `cfg(foo,test())`
+   |
+   = note: `test()` is invalid
+   = note: `cfg()` arguments must be simple identifiers, `any()` or `values(...)`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.unknown_meta_item_3.stderr

@@ -1,2 +1,6 @@
-error: invalid `--check-cfg` argument: `cfg(foo,values(test()))` (`values()` arguments must be string literals, `none()` or `any()`)
+error: invalid `--check-cfg` argument: `cfg(foo,values(test()))`
+   |
+   = note: `test()` is invalid
+   = note: `values()` arguments must be string literals, `none()` or `any()`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.unterminated.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(` (expected `cfg(name, values("value1", "value2", ... "valueN"))`)
+error: invalid `--check-cfg` argument: `cfg(`
+   |
+   = note: expected `cfg(name, values("value1", "value2", ... "valueN"))`
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.values_any_before_ident.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(values(any()),foo)` (`values()` cannot be specified before the names)
+error: invalid `--check-cfg` argument: `cfg(values(any()),foo)`
+   |
+   = note: `values()` cannot be specified before the names
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details
 

tests/ui/check-cfg/invalid-arguments.values_any_missing_values.stderr

@@ -1,2 +1,5 @@
-error: invalid `--check-cfg` argument: `cfg(foo,any())` (`cfg(any())` can only be provided in isolation)
+error: invalid `--check-cfg` argument: `cfg(foo,any())`
+   |
+   = note: `cfg(any())` can only be provided in isolation
+   = note: visit <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more details