provide suggestion for incorrect deprecated syntax

Author: euclio

src/libsyntax/attr/builtin.rs

@@ -10,7 +10,7 @@
 
 //! Parsing and validation of builtin attributes
 
-use ast::{self, Attribute, MetaItem, Name, NestedMetaItemKind};
+use ast::{self, Attribute, LitKind, MetaItem, Name, NestedMetaItemKind};
 use errors::{Applicability, Handler};
 use feature_gate::{Features, GatedCfg};
 use parse::ParseSess;
@@ -598,12 +598,10 @@ fn find_deprecation_generic<'a, I>(sess: &ParseSess,
     let diagnostic = &sess.span_diagnostic;
 
     'outer: for attr in attrs_iter {
-        if attr.path != "deprecated" {
+        if !attr.check_name("deprecated") {
             continue
         }
 
-        mark_used(attr);
-
         if depr.is_some() {
             span_err!(diagnostic, item_sp, E0550, "multiple deprecated attributes");
             break
@@ -670,6 +668,28 @@ fn find_deprecation_generic<'a, I>(sess: &ParseSess,
             }
 
             Some(Deprecation {since: since, note: note})
+        } else if let Some(lit) = attr
+            .meta()
+            .as_ref()
+            .and_then(|meta| meta.name_value_literal())
+        {
+            let mut err = sess
+                .span_diagnostic
+                .struct_span_err(attr.span, "expected meta item sequence");
+
+            if let LitKind::Str(s, _) = lit.node {
+                let sp = attr.path.span.to(lit.span);
+                err.span_suggestion_with_applicability(
+                    sp,
+                    "use the `note` key",
+                    format!("deprecated(note = \"{}\")", s),
+                    Applicability::MachineApplicable,
+                );
+            }
+
+            err.emit();
+
+            continue 'outer;
         } else {
             Some(Deprecation{since: None, note: None})
         }

src/test/ui/deprecation/deprecation-sanity.rs

@@ -34,4 +34,9 @@ fn multiple1() { } //~ ERROR multiple deprecated attributes
 #[deprecated(since = "a", since = "b", note = "c")] //~ ERROR multiple 'since' items
 fn f1() { }
 
+#[deprecated = "reason"]
+fn foo() { }             //~^ ERROR expected meta item sequence
+                         //~| HELP use the `note` key
+                         //~| SUGGESTION deprecated(note = "reason")
+
 fn main() { }

src/test/ui/deprecation/deprecation-sanity.stderr

@@ -40,7 +40,15 @@ error[E0538]: multiple 'since' items
 LL | #[deprecated(since = "a", since = "b", note = "c")] //~ ERROR multiple 'since' items
    |                           ^^^^^^^^^^^
 
-error: aborting due to 7 previous errors
+error: expected meta item sequence
+  --> $DIR/deprecation-sanity.rs:37:1
+   |
+LL | #[deprecated = "reason"]
+   | ^^---------------------^
+   |   |
+   |   help: use the `note` key: `deprecated(note = "reason")`
+
+error: aborting due to 8 previous errors
 
 Some errors occurred: E0538, E0541, E0550, E0551.
 For more information about an error, try `rustc --explain E0538`.

src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs

@@ -630,17 +630,17 @@ mod link_section {
 
 struct StructForDeprecated;
 
-#[deprecated = "1500"]
+#[deprecated]
 mod deprecated {
-    mod inner { #![deprecated="1500"] }
+    mod inner { #![deprecated] }
 
-    #[deprecated = "1500"] fn f() { }
+    #[deprecated] fn f() { }
 
-    #[deprecated = "1500"] struct S1;
+    #[deprecated] struct S1;
 
-    #[deprecated = "1500"] type T = super::StructForDeprecated;
+    #[deprecated] type T = super::StructForDeprecated;
 
-    #[deprecated = "1500"] impl super::StructForDeprecated { }
+    #[deprecated] impl super::StructForDeprecated { }
 }
 
 #[must_use = "1400"]

src/test/ui/feature-gate/issue-43106-gating-of-deprecated.rs

@@ -18,13 +18,7 @@
 // compile-pass
 // skip-codegen
 #![allow(dead_code)]
-#![deprecated           = "1100"]
-
-// Since we expect for the mix of attributes used here to compile
-// successfully, and we are just testing for the expected warnings of
-// various (mis)uses of attributes, we use the `rustc_error` attribute
-// on the `fn main()`.
-
+#![deprecated]
 
 fn main() {
     println!("Hello World");