Auto merge of #105880 - Nilstrieb:make-newtypes-less-not-rust, r=oli-obk

Improve syntax of `newtype_index`

This makes it more like proper Rust and also makes the implementation a lot simpler.

Mostly just turns weird flags in the body into proper attributes.

It should probably also be converted to an attribute macro instead of function-like, but that can be done in a future PR.

compiler/rustc_span/src/def_id.rs

@@ -10,10 +10,9 @@ use std::fmt;
 use std::hash::{Hash, Hasher};
 
 rustc_index::newtype_index! {
-    pub struct CrateNum {
-        ENCODABLE = custom
-        DEBUG_FORMAT = "crate{}"
-    }
+    #[custom_encodable]
+    #[debug_format = "crate{}"]
+    pub struct CrateNum {}
 }
 
 /// Item definitions in the currently-compiled crate would have the `CrateNum`
@@ -194,13 +193,12 @@ rustc_index::newtype_index! {
     /// A DefIndex is an index into the hir-map for a crate, identifying a
     /// particular definition. It should really be considered an interned
     /// shorthand for a particular DefPath.
+    #[custom_encodable] // (only encodable in metadata)
+    #[debug_format = "DefIndex({})"]
     pub struct DefIndex {
-        ENCODABLE = custom // (only encodable in metadata)
-
-        DEBUG_FORMAT = "DefIndex({})",
         /// The crate root is always assigned index 0 by the AST Map code,
         /// thanks to `NodeCollector::new`.
-        const CRATE_DEF_INDEX = 0,
+        const CRATE_DEF_INDEX = 0;
     }
 }
 

compiler/rustc_span/src/hygiene.rs

@@ -61,9 +61,8 @@ pub struct SyntaxContextData {
 
 rustc_index::newtype_index! {
     /// A unique ID associated with a macro invocation and expansion.
-    pub struct ExpnIndex {
-        ENCODABLE = custom
-    }
+    #[custom_encodable]
+    pub struct ExpnIndex {}
 }
 
 /// A unique ID associated with a macro invocation and expansion.
@@ -82,11 +81,10 @@ impl fmt::Debug for ExpnId {
 
 rustc_index::newtype_index! {
     /// A unique ID associated with a macro invocation and expansion.
-    pub struct LocalExpnId {
-        ENCODABLE = custom
-        ORD_IMPL = custom
-        DEBUG_FORMAT = "expn{}"
-    }
+    #[custom_encodable]
+    #[no_ord_impl]
+    #[debug_format = "expn{}"]
+    pub struct LocalExpnId {}
 }
 
 // To ensure correctness of incremental compilation,

compiler/rustc_span/src/symbol.rs

@@ -1802,7 +1802,7 @@ impl fmt::Display for MacroRulesNormalizedIdent {
 pub struct Symbol(SymbolIndex);
 
 rustc_index::newtype_index! {
-    struct SymbolIndex { .. }
+    struct SymbolIndex {}
 }
 
 impl Symbol {