Rollup merge of #136835 - compiler-errors:contracts-span-hack, r=celinval

Stop using span hack for contracts feature gating

The contracts machinery is a pretty straightforward case of an *external* feature using a (perma-unstable) *internal* feature within its implementation. There's no reason why it needs to be implemented any differently than other features by using global span tracking hacks to change whether the internals are gated behind the `contracts` or `contracts_internals` feature gate -- for the case of macro expansions we already have `allow_internal_unstable` for exactly this situation.

This PR changes the internal, perma-unstable AST syntax to use the `contracts_internals` gate always, and adjusts the macro expansion to use the right spans so that `allow_internal_unstable` works correctly.

As a follow-up, there's really no reason to have `contracts` be a *compiler feature* since it's at this point fully a *library feature*; the only reason it's a compiler feature today is so we can mark it as incomplete, but that seems like a weak reason. I didn't do anything in this PR for this.

r? ``@celinval``

1 files changed, 9 insertions, 14 deletions

diff --git a/compiler/rustc_builtin_macros/src/contracts.rs b/compiler/rustc_builtin_macros/src/contracts.rs
index 85a30f7bdc9..6a24af361fe 100644
--- a/compiler/rustc_builtin_macros/src/contracts.rs
+++ b/compiler/rustc_builtin_macros/src/contracts.rs
@@ -1,11 +1,9 @@
-#![allow(unused_imports, unused_variables)]
-
 use rustc_ast::token;
 use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
 use rustc_errors::ErrorGuaranteed;
 use rustc_expand::base::{AttrProcMacro, ExtCtxt};
 use rustc_span::Span;
-use rustc_span::symbol::{Ident, Symbol, kw, sym};
+use rustc_span::symbol::{Ident, Symbol, kw};
 
 pub(crate) struct ExpandRequires;
 
@@ -121,23 +119,19 @@ fn expand_contract_clause(
         }
     }
 
-    // Record the span as a contract attribute expansion.
-    // This is used later to stop users from using the extended syntax directly
-    // which is gated via `contracts_internals`.
-    ecx.psess().contract_attribute_spans.push(attr_span);
-
     Ok(new_tts)
 }
 
 fn expand_requires_tts(
-    _ecx: &mut ExtCtxt<'_>,
+    ecx: &mut ExtCtxt<'_>,
     attr_span: Span,
     annotation: TokenStream,
     annotated: TokenStream,
 ) -> Result<TokenStream, ErrorGuaranteed> {
-    expand_contract_clause(_ecx, attr_span, annotated, |new_tts| {
+    let feature_span = ecx.with_def_site_ctxt(attr_span);
+    expand_contract_clause(ecx, attr_span, annotated, |new_tts| {
         new_tts.push_tree(TokenTree::Token(
-            token::Token::from_ast_ident(Ident::new(kw::ContractRequires, attr_span)),
+            token::Token::from_ast_ident(Ident::new(kw::ContractRequires, feature_span)),
             Spacing::Joint,
         ));
         new_tts.push_tree(TokenTree::Token(
@@ -155,14 +149,15 @@ fn expand_requires_tts(
 }
 
 fn expand_ensures_tts(
-    _ecx: &mut ExtCtxt<'_>,
+    ecx: &mut ExtCtxt<'_>,
     attr_span: Span,
     annotation: TokenStream,
     annotated: TokenStream,
 ) -> Result<TokenStream, ErrorGuaranteed> {
-    expand_contract_clause(_ecx, attr_span, annotated, |new_tts| {
+    let feature_span = ecx.with_def_site_ctxt(attr_span);
+    expand_contract_clause(ecx, attr_span, annotated, |new_tts| {
         new_tts.push_tree(TokenTree::Token(
-            token::Token::from_ast_ident(Ident::new(kw::ContractEnsures, attr_span)),
+            token::Token::from_ast_ident(Ident::new(kw::ContractEnsures, feature_span)),
             Spacing::Joint,
         ));
         new_tts.push_tree(TokenTree::Delimited(