Port crate name to the new attribute system

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -367,6 +367,9 @@ pub enum AttributeKind {
     /// Represents `#[coverage(..)]`.
     Coverage(Span, CoverageAttrKind),
 
+    /// Represents `#[crate_name = ...]`
+    CrateName { name: Symbol, name_span: Span, attr_span: Span, style: AttrStyle },
+
     /// Represents `#[custom_mir]`.
     CustomMir(Option<(MirDialect, Span)>, Option<(MirPhase, Span)>, Span),
 

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -7,6 +7,11 @@ pub enum EncodeCrossCrate {
 }
 
 impl AttributeKind {
+    /// Whether this attribute should be encoded in metadata files.
+    ///
+    /// If this is "Yes", then another crate can do `tcx.get_all_attrs(did)` for a did in this crate, and get the attribute.
+    /// When this is No, the attribute is filtered out while encoding and other crate won't be able to observe it.
+    /// This can be unexpectedly good for performance, so unless necessary for cross-crate compilation, prefer No.
     pub fn encode_cross_crate(&self) -> EncodeCrossCrate {
         use AttributeKind::*;
         use EncodeCrossCrate::*;
@@ -31,6 +36,7 @@ impl AttributeKind {
             ConstTrait(..) => No,
             Coroutine(..) => No,
             Coverage(..) => No,
+            CrateName { .. } => No,
             CustomMir(_, _, _) => Yes,
             DenyExplicitImpl(..) => No,
             Deprecation { .. } => Yes,