Support multiple stability attributes on items

Cargo.lock

@@ -3334,6 +3334,7 @@ dependencies = [
  "rustc_serialize",
  "rustc_session",
  "rustc_span",
+ "smallvec",
 ]
 
 [[package]]
@@ -3506,6 +3507,7 @@ dependencies = [
  "rustc_target",
  "rustc_trait_selection",
  "rustc_type_ir",
+ "smallvec",
  "tracing",
 ]
 
@@ -3683,6 +3685,7 @@ dependencies = [
 name = "rustc_feature"
 version = "0.0.0"
 dependencies = [
+ "either",
  "rustc_data_structures",
  "rustc_span",
 ]
@@ -4217,6 +4220,7 @@ dependencies = [
  "rustc_span",
  "rustc_target",
  "rustc_trait_selection",
+ "smallvec",
  "tracing",
 ]
 

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -1,9 +1,9 @@
 use rustc_ast as ast;
 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
 use rustc_ast::{NodeId, PatKind, attr, token};
-use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute, Features, GateIssue};
+use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP, BuiltinAttribute, Features};
 use rustc_session::Session;
-use rustc_session::parse::{feature_err, feature_err_issue, feature_warn};
+use rustc_session::parse::{feature_err, feature_warn};
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::sym;
 use rustc_span::{Span, Symbol};
@@ -81,7 +81,7 @@ impl<'a> PostExpansionVisitor<'a> {
         match abi::is_enabled(self.features, span, symbol_unescaped.as_str()) {
             Ok(()) => (),
             Err(abi::AbiDisabled::Unstable { feature, explain }) => {
-                feature_err_issue(&self.sess, feature, span, GateIssue::Language, explain).emit();
+                feature_err(&self.sess, feature, span, explain).emit();
             }
             Err(abi::AbiDisabled::Unrecognized) => {
                 if self.sess.opts.pretty.map_or(true, |ppm| ppm.needs_hir()) {

compiler/rustc_attr/Cargo.toml

@@ -17,4 +17,5 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
+smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 # tidy-alphabetical-end

compiler/rustc_attr/messages.ftl

@@ -83,7 +83,10 @@ attr_multiple_item =
     multiple '{$item}' items
 
 attr_multiple_stability_levels =
-    multiple stability levels
+    multiple stability levels for feature `{$feature}`
+
+attr_multiple_unstable_reasons =
+    multiple reasons provided for unstability
 
 attr_non_ident_feature =
     'feature' is not an identifier
@@ -97,6 +100,9 @@ attr_rustc_const_stable_indirect_pairing =
 attr_rustc_promotable_pairing =
     `rustc_promotable` attribute must be paired with either a `rustc_const_unstable` or a `rustc_const_stable` attribute
 
+attr_soft_inconsistent =
+    `soft` must be present on either none or all of an item's `unstable` attributes
+
 attr_soft_no_args =
     `soft` should not have any arguments