Auto merge of #159046 - jhpratt:rollup-mqQhHMX, r=jhpratt

Rollup of 24 pull requests

Successful merges:

 - #150946 (intrinsics: Add a fallback for non-const libm float functions)
 - #158541 (Move `std::io::Write` to `core::io`)
 - #156027 (Consider captured regions for opaque type region liveness.)
 - #156370 (Reject linked dylib EII default overrides)
 - #156508 (Infer all anonymous lifetimes in assoc consts as `'static`)
 - #157561 (rustdoc: do not include extra stuff in span)
 - #158617 (allow mGCA const arguments to fall back to anon consts)
 - #158645 (Fix splat ICEs and ban it in closures)
 - #158859 (Improve `-Zls` diagnostic message on `.rs` files)
 - #158988 (Redo `TokenStreamIter`)
 - #158347 (Improve generic parameters handling for #[diagnostic::on_const])
 - #158384 (Allow BackwardIncompatibleDropHint in polonius legacy)
 - #158722 (delegation: do not always inherit `ConstArgHasType` predicates)
 - #158739 (view-types: HIR lowering)
 - #158877 (borrowck: Keep returned `path` from `best_blame_constraint()` consistent)
 - #158883 (tests: fix enum-match.rs to handle LLVM 23)
 - #158886 (Add documentation for the `no_std` attribute)
 - #158940 (Implement feature `char_to_u32`)
 - #158951 (Merge three `MaxUniverse`s into one)
 - #158960 (Fix bootstrap submodule path prefix matching)
 - #158961 (Reapply "LLVM 23: Run AssignGUIDPass in some places")
 - #158995 (Use REST API in linkchecker script)
 - #158996 ([compiler] Implement `PartialOrd` via `Ord` for `Span` and newtype_indexes)
 - #159036 (bootstrap: expand '@argfile' arguments to rustc shim)

Author: bors

compiler/rustc_ast/src/ast.rs

@@ -1378,15 +1378,6 @@ pub enum UnsafeSource {
     UserProvided,
 }
 
-/// Track whether under `feature(min_generic_const_args)` this anon const
-/// was explicitly disambiguated as an anon const or not through the use of
-/// `const { ... }` syntax.
-#[derive(Clone, PartialEq, Encodable, Decodable, Debug, Copy, Walkable)]
-pub enum MgcaDisambiguation {
-    AnonConst,
-    Direct,
-}
-
 /// A constant (expression) that's not an item or associated item,
 /// but needs its own `DefId` for type-checking, const-eval, etc.
 /// These are usually found nested inside types (e.g., array lengths)
@@ -1396,7 +1387,6 @@ pub enum MgcaDisambiguation {
 pub struct AnonConst {
     pub id: NodeId,
     pub value: Box<Expr>,
-    pub mgca_disambiguation: MgcaDisambiguation,
 }
 
 /// An expression.
@@ -1627,6 +1617,7 @@ impl Expr {
             | ExprKind::UnsafeBinderCast(..)
             | ExprKind::While(..)
             | ExprKind::Yield(YieldKind::Postfix(..))
+            | ExprKind::DirectConstArg(..)
             | ExprKind::Err(_)
             | ExprKind::Dummy => prefix_attrs_precedence(&self.attrs),
         }
@@ -1920,6 +1911,9 @@ pub enum ExprKind {
 
     UnsafeBinderCast(UnsafeBinderCastKind, Box<Expr>, Option<Box<Ty>>),
 
+    /// An mGCA `direct_const_arg!()` expression.
+    DirectConstArg(Box<Expr>),
+
     /// Placeholder for an expression that wasn't syntactically well formed in some way.
     Err(ErrorGuaranteed),
 
@@ -2566,6 +2560,8 @@ pub enum TyKind {
     FieldOf(Box<Ty>, Option<Ident>, Ident),
     /// A view of a type. `T.{ field_1, field_2 }`.
     View(Box<Ty>, #[visitable(ignore)] ThinVec<Ident>),
+    /// An mGCA `direct_const_arg!()` expression.
+    DirectConstArg(Box<Expr>),
     /// Sometimes we need a dummy value when no error has occurred.
     Dummy,
     /// Placeholder for a kind that has failed to be defined.
@@ -3066,6 +3062,9 @@ impl FnDecl {
     /// Must have the same value as `FnSigKind::NO_SPLATTED_ARG_INDEX` and `FnDeclFlags::NO_SPLATTED_ARG_INDEX`.
     pub const NO_SPLATTED_ARG_INDEX: u8 = u8::MAX;
 
+    /// The maximum valid splatted argument index.
+    pub const MAX_VALID_SPLATTED_ARG_INDEX: u8 = Self::NO_SPLATTED_ARG_INDEX - 1;
+
     /// Returns a splatted argument index, if any are present.
     pub fn splatted(&self) -> Option<u8> {
         self.inputs.iter().enumerate().find_map(|(index, arg)| {

compiler/rustc_ast/src/tokenstream.rs

@@ -22,6 +22,9 @@ use crate::ast_traits::{HasAttrs, HasTokens};
 use crate::token::{self, Delimiter, Token, TokenKind};
 use crate::{AttrVec, Attribute};
 
+#[cfg(test)]
+mod tests;
+
 /// Part of a `TokenStream`.
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Encodable, Decodable, StableHash)]
 pub enum TokenTree {
@@ -833,32 +836,30 @@ impl StableHash for TokenStream {
 }
 
 #[derive(Clone)]
-pub struct TokenStreamIter<'t> {
-    stream: &'t TokenStream,
-    index: usize,
-}
+pub struct TokenStreamIter<'t>(std::slice::Iter<'t, TokenTree>);
 
 impl<'t> TokenStreamIter<'t> {
     fn new(stream: &'t TokenStream) -> Self {
-        TokenStreamIter { stream, index: 0 }
+        TokenStreamIter(stream.0.as_slice().iter())
     }
 
     // Peeking could be done via `Peekable`, but most iterators need peeking,
     // and this is simple and avoids the need to use `peekable` and `Peekable`
     // at all the use sites.
     pub fn peek(&self) -> Option<&'t TokenTree> {
-        self.stream.0.get(self.index)
+        self.0.as_slice().first()
     }
 }
 
 impl<'t> Iterator for TokenStreamIter<'t> {
     type Item = &'t TokenTree;
 
     fn next(&mut self) -> Option<&'t TokenTree> {
-        self.stream.0.get(self.index).map(|tree| {
-            self.index += 1;
-            tree
-        })
+        self.0.next()
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
     }
 }
 

compiler/rustc_ast/src/tokenstream/tests.rs

@@ -0,0 +1,13 @@
+use rustc_span::DUMMY_SP;
+
+use crate::token::TokenKind;
+use crate::tokenstream::TokenStream;
+
+#[test]
+fn test_token_stream_iter() {
+    let ts = TokenStream::token_alone(TokenKind::Eq, DUMMY_SP);
+    assert_eq!(ts.len(), 1);
+
+    let iter = ts.iter();
+    assert_eq!(iter.size_hint(), (1, Some(1)));
+}

compiler/rustc_ast/src/util/classify.rs

@@ -155,6 +155,7 @@ pub fn leading_labeled_expr(mut expr: &ast::Expr) -> bool {
             | Yeet(..)
             | Yield(..)
             | UnsafeBinderCast(..)
+            | DirectConstArg(..)
             | Err(..)
             | Dummy => return false,
         }
@@ -240,6 +241,7 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<TrailingBrace<'_>> {
             | Try(_)
             | Yeet(None)
             | UnsafeBinderCast(..)
+            | DirectConstArg(..)
             | Err(_)
             | Dummy => {
                 break None;
@@ -301,9 +303,10 @@ fn type_trailing_braced_mac_call(mut ty: &ast::Ty) -> Option<&ast::MacCall> {
             | ast::TyKind::CVarArgs
             | ast::TyKind::Pat(..)
             | ast::TyKind::FieldOf(..)
+            | ast::TyKind::View(..)
+            | ast::TyKind::DirectConstArg(..)
             | ast::TyKind::Dummy
-            | ast::TyKind::Err(..)
-            | ast::TyKind::View(..) => break None,
+            | ast::TyKind::Err(..) => break None,
         }
     }
 }

compiler/rustc_ast/src/visit.rs

@@ -418,7 +418,6 @@ macro_rules! common_visitor_and_walkers {
             UnsafeBinderCastKind,
             BinOpKind,
             BlockCheckMode,
-            MgcaDisambiguation,
             BorrowKind,
             BoundAsyncness,
             BoundConstness,
@@ -1074,6 +1073,8 @@ macro_rules! common_visitor_and_walkers {
                     visit_visitable!($($mut)? vis, bytes),
                 ExprKind::UnsafeBinderCast(kind, expr, ty) =>
                     visit_visitable!($($mut)? vis, kind, expr, ty),
+                ExprKind::DirectConstArg(expr) =>
+                    visit_visitable!($($mut)? vis, expr),
                 ExprKind::Err(_guar) => {}
                 ExprKind::Dummy => {}
             }

compiler/rustc_ast_lowering/src/expr.rs

@@ -498,6 +498,18 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
 
                 ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
+
+                ExprKind::DirectConstArg(_) => {
+                    let e = self
+                        .tcx
+                        .dcx()
+                        .struct_span_err(
+                            e.span,
+                            "expected expression, found `direct_const_arg!()` constant",
+                        )
+                        .emit();
+                    hir::ExprKind::Err(e)
+                }
             };
 
             hir::Expr { hir_id: expr_hir_id, kind, span }
@@ -599,11 +611,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         arg
                     };
 
-                let anon_const = AnonConst {
-                    id: node_id,
-                    value: const_value,
-                    mgca_disambiguation: MgcaDisambiguation::AnonConst,
-                };
+                let anon_const = AnonConst { id: node_id, value: const_value };
                 generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const)));
             } else {
                 real_args.push(arg);