Auto merge of #57321 - petrochenkov:atokens, r=nikomatsakis

Implement basic input validation for built-in attributes

Correct top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is enforced for built-in attributes, built-in attributes must also fit into the "meta-item" syntax (aka the "classic attribute syntax").

For some subset of attributes (found by crater run), errors are lowered to deprecation warnings.

NOTE: This PR previously included #57367 as well.

src/librustc/diagnostics.rs

@@ -1180,27 +1180,6 @@ fn main() {
 ```
 "##,
 
-E0296: r##"
-This error indicates that the given recursion limit could not be parsed. Ensure
-that the value provided is a positive integer between quotes.
-
-Erroneous code example:
-
-```compile_fail,E0296
-#![recursion_limit]
-
-fn main() {}
-```
-
-And a working example:
-
-```
-#![recursion_limit="1000"]
-
-fn main() {}
-```
-"##,
-
 E0308: r##"
 This error occurs when the compiler was unable to infer the concrete type of a
 variable. It can occur for several cases, the most common of which is a
@@ -2093,20 +2072,6 @@ trait Foo { }
 ```
 "##,
 
-E0702: r##"
-This error indicates that a `#[non_exhaustive]` attribute had a value. The
-`#[non_exhaustive]` should be empty.
-
-Examples of erroneous code:
-
-```compile_fail,E0702
-# #![feature(non_exhaustive)]
-
-#[non_exhaustive(anything)]
-struct Foo;
-```
-"##,
-
 E0718: r##"
 This error indicates that a `#[lang = ".."]` attribute was placed
 on the wrong type of item.
@@ -2138,6 +2103,7 @@ register_diagnostics! {
     E0280, // requirement is not satisfied
     E0284, // cannot resolve type
 //  E0285, // overflow evaluation builtin bounds
+//  E0296, // replaced with a generic attribute input check
 //  E0300, // unexpanded macro
 //  E0304, // expected signed integer constant
 //  E0305, // expected constant
@@ -2180,4 +2146,5 @@ register_diagnostics! {
     E0709, // multiple different lifetimes used in arguments of `async fn`
     E0710, // an unknown tool name found in scoped lint
     E0711, // a feature has been declared with conflicting stability attributes
+//  E0702, // replaced with a generic attribute input check
 }

src/librustc/hir/check_attr.rs

@@ -142,15 +142,6 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
                 return;
             }
         }
-
-        if attr.meta_item_list().is_some() || attr.value_str().is_some() {
-            struct_span_err!(self.tcx.sess,
-                             attr.span,
-                             E0702,
-                             "attribute should be empty")
-                .span_label(item.span, "not empty")
-                .emit();
-        }
     }
 
     /// Check if the `#[marker]` attribute on an `item` is valid.
@@ -165,12 +156,6 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
                 return;
             }
         }
-
-        if !attr.is_word() {
-            self.tcx.sess
-                .struct_span_err(attr.span, "attribute should be empty")
-                .emit();
-        }
     }
 
     /// Check if the `#[repr]` attributes on `item` are valid.

src/librustc/lint/builtin.rs

@@ -204,12 +204,6 @@ declare_lint! {
     "trait-object types were treated as different depending on marker-trait order"
 }
 
-declare_lint! {
-    pub BAD_REPR,
-    Warn,
-    "detects incorrect use of `repr` attribute"
-}
-
 declare_lint! {
     pub DEPRECATED,
     Warn,
@@ -359,6 +353,12 @@ pub mod parser {
         Allow,
         "detects the use of `?` as a macro separator"
     }
+
+    declare_lint! {
+        pub ILL_FORMED_ATTRIBUTE_INPUT,
+        Warn,
+        "ill-formed attribute inputs that were previously accepted and used in practice"
+    }
 }
 
 declare_lint! {
@@ -431,6 +431,7 @@ impl LintPass for HardwiredLints {
             MACRO_USE_EXTERN_CRATE,
             MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
             parser::QUESTION_MARK_MACRO_SEP,
+            parser::ILL_FORMED_ATTRIBUTE_INPUT,
             DEPRECATED_IN_FUTURE,
         )
     }

src/librustc/lint/levels.rs

@@ -204,8 +204,6 @@ impl<'a> LintLevelsBuilder<'a> {
             let mut metas = if let Some(metas) = meta.meta_item_list() {
                 metas
             } else {
-                let mut err = bad_attr(meta.span);
-                err.emit();
                 continue;
             };
 

src/librustc/lint/mod.rs

@@ -28,7 +28,7 @@ use hir::def_id::{CrateNum, LOCAL_CRATE};
 use hir::intravisit;
 use hir;
 use lint::builtin::BuiltinLintDiagnostics;
-use lint::builtin::parser::QUESTION_MARK_MACRO_SEP;
+use lint::builtin::parser::{QUESTION_MARK_MACRO_SEP, ILL_FORMED_ATTRIBUTE_INPUT};
 use session::{Session, DiagnosticMessageId};
 use std::{hash, ptr};
 use syntax::ast;
@@ -82,6 +82,7 @@ impl Lint {
     pub fn from_parser_lint_id(lint_id: BufferedEarlyLintId) -> &'static Self {
         match lint_id {
             BufferedEarlyLintId::QuestionMarkMacroSep => QUESTION_MARK_MACRO_SEP,
+            BufferedEarlyLintId::IllFormedAttributeInput => ILL_FORMED_ATTRIBUTE_INPUT,
         }
     }
 

src/librustc/middle/recursion_limit.rs

@@ -11,14 +11,11 @@ use syntax::ast;
 use rustc_data_structures::sync::Once;
 
 pub fn update_limits(sess: &Session, krate: &ast::Crate) {
-    update_limit(sess, krate, &sess.recursion_limit, "recursion_limit",
-                 "recursion limit", 64);
-    update_limit(sess, krate, &sess.type_length_limit, "type_length_limit",
-                 "type length limit", 1048576);
+    update_limit(krate, &sess.recursion_limit, "recursion_limit", 64);
+    update_limit(krate, &sess.type_length_limit, "type_length_limit", 1048576);
 }
 
-fn update_limit(sess: &Session, krate: &ast::Crate, limit: &Once<usize>,
-                name: &str, description: &str, default: usize) {
+fn update_limit(krate: &ast::Crate, limit: &Once<usize>, name: &str, default: usize) {
     for attr in &krate.attrs {
         if !attr.check_name(name) {
             continue;
@@ -30,10 +27,6 @@ fn update_limit(sess: &Session, krate: &ast::Crate, limit: &Once<usize>,
                 return;
             }
         }
-
-        span_err!(sess, attr.span, E0296,
-                  "malformed {} attribute, expected #![{}=\"N\"]",
-                  description, name);
     }
     limit.set(default);
 }

src/librustc/traits/on_unimplemented.rs

@@ -157,10 +157,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedDirective {
                 note: None,
             }))
         } else {
-            return Err(parse_error(tcx, attr.span,
-                                   "`#[rustc_on_unimplemented]` requires a value",
-                                   "value required here",
-                                   Some(r#"eg `#[rustc_on_unimplemented(message="foo")]`"#)));
+            return Err(ErrorReported);
         };
         debug!("of_item({:?}/{:?}) = {:?}", trait_def_id, impl_def_id, result);
         result

src/librustc_driver/driver.rs

@@ -1070,15 +1070,6 @@ where
         )
     });
 
-    // Add all buffered lints from the `ParseSess` to the `Session`.
-    sess.parse_sess.buffered_lints.with_lock(|buffered_lints| {
-        info!("{} parse sess buffered_lints", buffered_lints.len());
-        for BufferedEarlyLint{id, span, msg, lint_id} in buffered_lints.drain(..) {
-            let lint = lint::Lint::from_parser_lint_id(lint_id);
-            sess.buffer_lint(lint, id, span, &msg);
-        }
-    });
-
     // Done with macro expansion!
 
     after_expand(&krate)?;
@@ -1114,6 +1105,15 @@ where
         );
     });
 
+    // Add all buffered lints from the `ParseSess` to the `Session`.
+    sess.parse_sess.buffered_lints.with_lock(|buffered_lints| {
+        info!("{} parse sess buffered_lints", buffered_lints.len());
+        for BufferedEarlyLint{id, span, msg, lint_id} in buffered_lints.drain(..) {
+            let lint = lint::Lint::from_parser_lint_id(lint_id);
+            sess.buffer_lint(lint, id, span, &msg);
+        }
+    });
+
     // Lower ast -> hir.
     // First, we need to collect the dep_graph.
     let dep_graph = match future_dep_graph {
@@ -1530,13 +1530,7 @@ pub fn collect_crate_types(session: &Session, attrs: &[ast::Attribute]) -> Vec<c
                         }
                         None
                     }
-                    None => {
-                        session
-                            .struct_span_err(a.span, "`crate_type` requires a value")
-                            .note("for example: `#![crate_type=\"lib\"]`")
-                            .emit();
-                        None
-                    }
+                    None => None
                 }
             } else {
                 None

src/librustc_lint/builtin.rs

@@ -35,7 +35,8 @@ use syntax::ast::Expr;
 use syntax::attr;
 use syntax::source_map::Spanned;
 use syntax::edition::Edition;
-use syntax::feature_gate::{AttributeGate, AttributeType, Stability, deprecated_attributes};
+use syntax::feature_gate::{AttributeGate, AttributeTemplate, AttributeType};
+use syntax::feature_gate::{Stability, deprecated_attributes};
 use syntax_pos::{BytePos, Span, SyntaxContext};
 use syntax::symbol::keywords;
 use syntax::errors::{Applicability, DiagnosticBuilder};
@@ -689,86 +690,12 @@ impl EarlyLintPass for AnonymousParameters {
     }
 }
 
-/// Checks for incorrect use of `repr` attributes.
-#[derive(Clone)]
-pub struct BadRepr;
-
-impl LintPass for BadRepr {
-    fn get_lints(&self) -> LintArray {
-        lint_array!()
-    }
-}
-
-impl EarlyLintPass for BadRepr {
-    fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
-        if attr.name() == "repr" {
-            let list = attr.meta_item_list();
-
-            let repr_str = |lit: &str| { format!("#[repr({})]", lit) };
-
-            // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
-            // no hints (``#[repr]`)
-            let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
-            if !has_hints {
-                let mut suggested = false;
-                let mut warn = if let Some(ref lit) = attr.value_str() {
-                    // avoid warning about empty `repr` on `#[repr = "foo"]`
-                    let mut warn = cx.struct_span_lint(
-                        BAD_REPR,
-                        attr.span,
-                        "`repr` attribute isn't configurable with a literal",
-                    );
-                    match lit.to_string().as_ref() {
-                        | "C" | "packed" | "rust" | "transparent"
-                        | "u8" | "u16" | "u32" | "u64" | "u128" | "usize"
-                        | "i8" | "i16" | "i32" | "i64" | "i128" | "isize" => {
-                            // if the literal could have been a valid `repr` arg,
-                            // suggest the correct syntax
-                            warn.span_suggestion_with_applicability(
-                                attr.span,
-                                "give `repr` a hint",
-                                repr_str(&lit.as_str()),
-                                Applicability::MachineApplicable
-                            );
-                            suggested = true;
-                        }
-                        _ => {  // the literal wasn't a valid `repr` arg
-                            warn.span_label(attr.span, "needs a hint");
-                        }
-                    };
-                    warn
-                } else {
-                    let mut warn = cx.struct_span_lint(
-                        BAD_REPR,
-                        attr.span,
-                        "`repr` attribute must have a hint",
-                    );
-                    warn.span_label(attr.span, "needs a hint");
-                    warn
-                };
-                if !suggested {
-                    warn.help(&format!(
-                        "valid hints include `{}`, `{}`, `{}` and `{}`",
-                        repr_str("C"),
-                        repr_str("packed"),
-                        repr_str("rust"),
-                        repr_str("transparent"),
-                    ));
-                    warn.note("for more information, visit \
-                               <https://doc.rust-lang.org/reference/type-layout.html>");
-                }
-                warn.emit();
-            }
-        }
-    }
-}
-
 /// Checks for use of attributes which have been deprecated.
 #[derive(Clone)]
 pub struct DeprecatedAttr {
     // This is not free to compute, so we want to keep it around, rather than
     // compute it for every attribute.
-    depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeGate)>,
+    depr_attrs: Vec<&'static (&'static str, AttributeType, AttributeTemplate, AttributeGate)>,
 }
 
 impl DeprecatedAttr {
@@ -787,7 +714,7 @@ impl LintPass for DeprecatedAttr {
 
 impl EarlyLintPass for DeprecatedAttr {
     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
-        for &&(n, _, ref g) in &self.depr_attrs {
+        for &&(n, _, _, ref g) in &self.depr_attrs {
             if attr.name() == n {
                 if let &AttributeGate::Gated(Stability::Deprecated(link, suggestion),
                                              ref name,

src/librustc_lint/lib.rs

@@ -48,7 +48,8 @@ use rustc::lint::builtin::{
     INTRA_DOC_LINK_RESOLUTION_FAILURE,
     MISSING_DOC_CODE_EXAMPLES,
     PRIVATE_DOC_TESTS,
-    parser::QUESTION_MARK_MACRO_SEP
+    parser::QUESTION_MARK_MACRO_SEP,
+    parser::ILL_FORMED_ATTRIBUTE_INPUT,
 };
 use rustc::session;
 use rustc::util;
@@ -114,7 +115,6 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                        UnsafeCode,
                        AnonymousParameters,
                        UnusedDocComment,
-                       BadRepr,
                        EllipsisInclusiveRangePatterns,
                        NonCamelCaseTypes,
                        );
@@ -336,6 +336,11 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
             reference: "issue #52234 <https://github.com/rust-lang/rust/issues/52234>",
             edition: None,
         },
+        FutureIncompatibleInfo {
+            id: LintId::of(ILL_FORMED_ATTRIBUTE_INPUT),
+            reference: "issue #57571 <https://github.com/rust-lang/rust/issues/57571>",
+            edition: None,
+        },
         ]);
 
     // Register renamed and removed lints.
@@ -385,4 +390,6 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
         "no longer a warning, #[no_mangle] functions always exported");
     store.register_removed("private_no_mangle_statics",
         "no longer a warning, #[no_mangle] statics always exported");
+    store.register_removed("bad_repr",
+        "replaced with a generic attribute input check");
 }