Auto merge of #115009 - matthiaskrgr:rollup-ainf2gb, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #114605 (Increase clarity about Hash - Eq consistency in HashMap and HashSet docs)
 - #114934 (instantiate response: no unnecessary new universe)
 - #114950 (Inline strlen_rt in CStr::from_ptr)
 - #114973 (Expose core::error::request_value in std)
 - #114983 (Usage zero as language id for `FormatMessageW()`)
 - #114991 (remove redundant var rebindings)
 - #114992 (const-eval: ensure we never const-execute a function marked rustc_do_not_const_check)
 - #115001 (clippy::perf stuff)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -427,52 +427,41 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
 
     fn find_mir_or_eval_fn(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
-        instance: ty::Instance<'tcx>,
+        orig_instance: ty::Instance<'tcx>,
         _abi: CallAbi,
         args: &[FnArg<'tcx>],
         dest: &PlaceTy<'tcx>,
         ret: Option<mir::BasicBlock>,
         _unwind: mir::UnwindAction, // unwinding is not supported in consts
     ) -> InterpResult<'tcx, Option<(&'mir mir::Body<'tcx>, ty::Instance<'tcx>)>> {
-        debug!("find_mir_or_eval_fn: {:?}", instance);
+        debug!("find_mir_or_eval_fn: {:?}", orig_instance);
+
+        // Replace some functions.
+        let Some(instance) = ecx.hook_special_const_fn(orig_instance, args, dest, ret)? else {
+            // Call has already been handled.
+            return Ok(None);
+        };
 
         // Only check non-glue functions
         if let ty::InstanceDef::Item(def) = instance.def {
             // Execution might have wandered off into other crates, so we cannot do a stability-
-            // sensitive check here. But we can at least rule out functions that are not const
-            // at all.
-            if !ecx.tcx.is_const_fn_raw(def) {
-                // allow calling functions inside a trait marked with #[const_trait].
-                if !ecx.tcx.is_const_default_method(def) {
-                    // We certainly do *not* want to actually call the fn
-                    // though, so be sure we return here.
-                    throw_unsup_format!("calling non-const function `{}`", instance)
-                }
-            }
-
-            let Some(new_instance) = ecx.hook_special_const_fn(instance, args, dest, ret)? else {
-                return Ok(None);
-            };
-
-            if new_instance != instance {
-                // We call another const fn instead.
-                // However, we return the *original* instance to make backtraces work out
-                // (and we hope this does not confuse the FnAbi checks too much).
-                return Ok(Self::find_mir_or_eval_fn(
-                    ecx,
-                    new_instance,
-                    _abi,
-                    args,
-                    dest,
-                    ret,
-                    _unwind,
-                )?
-                .map(|(body, _instance)| (body, instance)));
+            // sensitive check here. But we can at least rule out functions that are not const at
+            // all. That said, we have to allow calling functions inside a trait marked with
+            // #[const_trait]. These *are* const-checked!
+            // FIXME: why does `is_const_fn_raw` not classify them as const?
+            if (!ecx.tcx.is_const_fn_raw(def) && !ecx.tcx.is_const_default_method(def))
+                || ecx.tcx.has_attr(def, sym::rustc_do_not_const_check)
+            {
+                // We certainly do *not* want to actually call the fn
+                // though, so be sure we return here.
+                throw_unsup_format!("calling non-const function `{}`", instance)
             }
         }
 
         // This is a const fn. Call it.
-        Ok(Some((ecx.load_mir(instance.def, None)?, instance)))
+        // In case of replacement, we return the *original* instance to make backtraces work out
+        // (and we hope this does not confuse the FnAbi checks too much).
+        Ok(Some((ecx.load_mir(instance.def, None)?, orig_instance)))
     }
 
     fn call_intrinsic(

compiler/rustc_hir_typeck/src/method/prelude2021.rs

@@ -14,6 +14,7 @@ use rustc_span::symbol::kw::{Empty, Underscore};
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
+use std::fmt::Write;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(super) fn lint_dot_call_from_2018(
@@ -143,16 +144,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                     let (self_adjusted, precise) = self.adjust_expr(pick, self_expr, sp);
                     if precise {
-                        let args = args
-                            .iter()
-                            .map(|arg| {
-                                let span = arg.span.find_ancestor_inside(sp).unwrap_or_default();
-                                format!(
-                                    ", {}",
-                                    self.sess().source_map().span_to_snippet(span).unwrap()
-                                )
-                            })
-                            .collect::<String>();
+                        let args = args.iter().fold(String::new(), |mut string, arg| {
+                            let span = arg.span.find_ancestor_inside(sp).unwrap_or_default();
+                            write!(
+                                string,
+                                ", {}",
+                                self.sess().source_map().span_to_snippet(span).unwrap()
+                            )
+                            .unwrap();
+                            string
+                        });
 
                         lint.span_suggestion(
                             sp,

compiler/rustc_middle/src/hir/mod.rs

@@ -164,18 +164,15 @@ pub fn provide(providers: &mut Providers) {
         tcx.hir_crate(()).owners[id.def_id].as_owner().map_or(AttributeMap::EMPTY, |o| &o.attrs)
     };
     providers.def_span = |tcx, def_id| {
-        let def_id = def_id;
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         tcx.hir().opt_span(hir_id).unwrap_or(DUMMY_SP)
     };
     providers.def_ident_span = |tcx, def_id| {
-        let def_id = def_id;
         let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
         tcx.hir().opt_ident_span(hir_id)
     };
-    providers.fn_arg_names = |tcx, id| {
+    providers.fn_arg_names = |tcx, def_id| {
         let hir = tcx.hir();
-        let def_id = id;
         let hir_id = hir.local_def_id_to_hir_id(def_id);
         if let Some(body_id) = hir.maybe_body_owned_by(def_id) {
             tcx.arena.alloc_from_iter(hir.body_param_names(body_id))
@@ -190,7 +187,7 @@ pub fn provide(providers: &mut Providers) {
         {
             idents
         } else {
-            span_bug!(hir.span(hir_id), "fn_arg_names: unexpected item {:?}", id);
+            span_bug!(hir.span(hir_id), "fn_arg_names: unexpected item {:?}", def_id);
         }
     };
     providers.opt_def_kind = |tcx, def_id| tcx.hir().opt_def_kind(def_id);

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -1,6 +1,7 @@
 //! Diagnostics related methods for `Ty`.
 
 use std::borrow::Cow;
+use std::fmt::Write;
 use std::ops::ControlFlow;
 
 use crate::ty::{
@@ -335,10 +336,10 @@ pub fn suggest_constraining_type_params<'a>(
             //                                           - insert: `, X: Bar`
             suggestions.push((
                 generics.tail_span_for_predicate_suggestion(),
-                constraints
-                    .iter()
-                    .map(|&(constraint, _)| format!(", {param_name}: {constraint}"))
-                    .collect::<String>(),
+                constraints.iter().fold(String::new(), |mut string, &(constraint, _)| {
+                    write!(string, ", {param_name}: {constraint}").unwrap();
+                    string
+                }),
                 SuggestChangingConstraintsMessage::RestrictTypeFurther { ty: param_name },
             ));
             continue;

compiler/rustc_mir_transform/src/coverage/debug.rs

@@ -199,9 +199,9 @@ impl DebugOptions {
 
 fn bool_option_val(option: &str, some_strval: Option<&str>) -> bool {
     if let Some(val) = some_strval {
-        if vec!["yes", "y", "on", "true"].contains(&val) {
+        if ["yes", "y", "on", "true"].contains(&val) {
             true
-        } else if vec!["no", "n", "off", "false"].contains(&val) {
+        } else if ["no", "n", "off", "false"].contains(&val) {
             false
         } else {
             bug!(

compiler/rustc_passes/src/layout_test.rs

@@ -27,7 +27,6 @@ pub fn test_layout(tcx: TyCtxt<'_>) {
 }
 
 fn dump_layout_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
-    let tcx = tcx;
     let param_env = tcx.param_env(item_def_id);
     let ty = tcx.type_of(item_def_id).instantiate_identity();
     match tcx.layout_of(param_env.and(ty)) {

compiler/rustc_passes/src/liveness.rs

@@ -1105,7 +1105,6 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                 }
 
                 // Then do a second pass for inputs
-                let mut succ = succ;
                 for (op, _op_sp) in asm.operands.iter().rev() {
                     match op {
                         hir::InlineAsmOperand::In { expr, .. } => {

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -215,7 +215,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         // created inside of the query directly instead of returning them to the
         // caller.
         let prev_universe = self.infcx.universe();
-        let universes_created_in_query = response.max_universe.index() + 1;
+        let universes_created_in_query = response.max_universe.index();
         for _ in 0..universes_created_in_query {
             self.infcx.create_next_universe();
         }

library/core/src/ffi/c_str.rs

@@ -253,7 +253,7 @@ impl CStr {
     /// ```
     ///
     /// [valid]: core::ptr#safety
-    #[inline]
+    #[inline] // inline is necessary for codegen to see strlen.
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_cstr_from_ptr", issue = "113219")]
@@ -280,6 +280,8 @@ impl CStr {
                 len
             }
 
+            // `inline` is necessary for codegen to see strlen.
+            #[inline]
             fn strlen_rt(s: *const c_char) -> usize {
                 extern "C" {
                     /// Provided by libc or compiler_builtins.

library/std/src/collections/hash/map.rs

@@ -49,12 +49,14 @@ use crate::sys;
 /// ```
 ///
 /// In other words, if two keys are equal, their hashes must be equal.
+/// Violating this property is a logic error.
 ///
-/// It is a logic error for a key to be modified in such a way that the key's
+/// It is also a logic error for a key to be modified in such a way that the key's
 /// hash, as determined by the [`Hash`] trait, or its equality, as determined by
 /// the [`Eq`] trait, changes while it is in the map. This is normally only
 /// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
-/// The behavior resulting from such a logic error is not specified, but will
+///
+/// The behavior resulting from either logic error is not specified, but will
 /// be encapsulated to the `HashMap` that observed the logic error and not
 /// result in undefined behavior. This could include panics, incorrect results,
 /// aborts, memory leaks, and non-termination.

library/std/src/collections/hash/set.rs

@@ -24,13 +24,14 @@ use super::map::{map_try_reserve_error, RandomState};
 /// ```
 ///
 /// In other words, if two keys are equal, their hashes must be equal.
+/// Violating this property is a logic error.
 ///
-///
-/// It is a logic error for a key to be modified in such a way that the key's
+/// It is also a logic error for a key to be modified in such a way that the key's
 /// hash, as determined by the [`Hash`] trait, or its equality, as determined by
 /// the [`Eq`] trait, changes while it is in the map. This is normally only
 /// possible through [`Cell`], [`RefCell`], global state, I/O, or unsafe code.
-/// The behavior resulting from such a logic error is not specified, but will
+///
+/// The behavior resulting from either logic error is not specified, but will
 /// be encapsulated to the `HashSet` that observed the logic error and not
 /// result in undefined behavior. This could include panics, incorrect results,
 /// aborts, memory leaks, and non-termination.

library/std/src/error.rs

@@ -10,7 +10,7 @@ use crate::fmt::{self, Write};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::error::Error;
 #[unstable(feature = "error_generic_member_access", issue = "99301")]
-pub use core::error::{request_ref, Request};
+pub use core::error::{request_ref, request_value, Request};
 
 mod private {
     // This is a hack to prevent `type_id` from being overridden by `Error`

library/std/src/sys/windows/os.rs

@@ -25,10 +25,6 @@ pub fn errno() -> i32 {
 
 /// Gets a detailed string description for the given error number.
 pub fn error_string(mut errnum: i32) -> String {
-    // This value is calculated from the macro
-    // MAKELANGID(LANG_SYSTEM_DEFAULT, SUBLANG_SYS_DEFAULT)
-    let langId = 0x0800 as c::DWORD;
-
     let mut buf = [0 as c::WCHAR; 2048];
 
     unsafe {
@@ -56,13 +52,13 @@ pub fn error_string(mut errnum: i32) -> String {
             flags | c::FORMAT_MESSAGE_FROM_SYSTEM | c::FORMAT_MESSAGE_IGNORE_INSERTS,
             module,
             errnum as c::DWORD,
-            langId,
+            0,
             buf.as_mut_ptr(),
             buf.len() as c::DWORD,
             ptr::null(),
         ) as usize;
         if res == 0 {
-            // Sometimes FormatMessageW can fail e.g., system doesn't like langId,
+            // Sometimes FormatMessageW can fail e.g., system doesn't like 0 as langId,
             let fm_err = errno();
             return format!("OS Error {errnum} (FormatMessageW() returned error {fm_err})");
         }

tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-1.rs

@@ -0,0 +1,73 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+// A minimization of an ambiguity when using typenum. See
+// https://github.com/rust-lang/trait-system-refactor-initiative/issues/55
+// for more details.
+trait Id {
+    type Assoc: ?Sized;
+}
+impl<T: ?Sized> Id for T {
+    type Assoc = T;
+}
+
+trait WithAssoc<T: ?Sized> {
+    type Assoc: ?Sized;
+}
+
+
+struct Leaf;
+struct Wrapper<U: ?Sized>(U);
+
+impl<U: ?Sized> WithAssoc<U> for Leaf {
+    type Assoc = U;
+}
+
+impl<Ul: ?Sized, Ur: ?Sized> WithAssoc<Wrapper<Ur>> for Wrapper<Ul>
+where
+    Ul: WithAssoc<Ur>,
+{
+    type Assoc = <<Ul as WithAssoc<Ur>>::Assoc as Id>::Assoc;
+}
+
+fn bound<T: ?Sized, U: ?Sized, V: ?Sized>()
+where
+    T: WithAssoc<U, Assoc = V>,
+{
+}
+
+// normalize self type to `Wrapper<Leaf>`
+//   This succeeds, HOWEVER, instantiating the query response previously
+//   incremented the universe index counter.
+// equate impl headers:
+//      <Wrapper<Leaf> as WithAssoc<<Wrapper<Leaf> as Id>::Assoc>>
+//      <Wrapper<?2t> as WithAssoc<Wrapper<?3t>>>
+// ~> AliasRelate(<Wrapper<Leaf> as Id>::Assoc, Equate, Wrapper<?3t>)
+// add where bounds:
+// ~> Leaf: WithAssoc<?3t>
+// equate with assoc type:
+//      ?0t
+//      <Leaf as WithAssoc<?3t>>::Assoc as Id>::Assoc
+// ~> AliasRelate(
+//      <<Leaf as WithAssoc<?3t>>::Assoc as Id>::Assoc,
+//      Equate,
+//      <<Leaf as WithAssoc<?4t>>::Assoc as Id>::Assoc,
+//    )
+//
+// We do not reuse `?3t` during generalization because `?0t` cannot name `?4t` as we created
+// it after incrementing the universe index while normalizing the self type.
+//
+// evaluate_added_goals_and_make_query_response:
+//    AliasRelate(<Wrapper<Leaf> as Id>::Assoc, Equate, Wrapper<?3t>)
+//      YES, constrains ?3t to Leaf
+//    AliasRelate(
+//      <<Leaf as WithAssoc<Leaf>>::Assoc as Id>::Assoc,
+//      Equate,
+//      <<Leaf as WithAssoc<?4t>>::Assoc as Id>::Assoc,
+//    )
+//
+// Normalizing <<Leaf as WithAssoc<?4t>>::Assoc as Id>::Assoc then *correctly*
+// results in ambiguity.
+fn main() {
+    bound::<<Wrapper<Leaf> as Id>::Assoc, <Wrapper<Leaf> as Id>::Assoc, _>()
+}

tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-2.rs

@@ -0,0 +1,75 @@
+// compile-flags: -Ztrait-solver=next
+// known-bug: trait-system-refactor-initiative#60
+
+// Generalizing a projection containing an inference variable
+// which cannot be named by the `root_vid` can result in ambiguity.
+//
+// Because we do not decrement the universe index when exiting a forall,
+// this can cause unexpected failures.
+//
+// See generalize-proj-new-universe-index-1.rs for more details.
+
+// For this reproduction we need:
+// - an inference variable with a lower universe
+// - enter a binder to increment the current universe
+// - create a new inference variable which is constrained by proving a goal
+// - equate a projection containing the new variable with the first variable
+// - generalization creates yet another inference variable which is then
+//   part of an alias-relate, resulting this to fail with ambiguity.
+//
+// Because we need to enter the binder in-between the creation of the first
+// and second inference variable, this is easiest via
+// `assemble_candidates_after_normalizing_self_ty` because eagerly call
+// `try_evaluate_added_goals` there before creating the inference variables
+// for the impl parameters.
+trait Id {
+    type Assoc: ?Sized;
+}
+impl<T: ?Sized> Id for T {
+    type Assoc = T;
+}
+
+// By adding an higher ranked bound to the impl we currently
+// propagate this bound to the caller, forcing us to create a new
+// universe.
+trait IdHigherRankedBound {
+    type Assoc: ?Sized;
+}
+
+impl<T: ?Sized> IdHigherRankedBound for T
+where
+    for<'a> T: 'a,
+{
+    type Assoc = T;
+}
+
+trait WithAssoc<T: ?Sized> {
+    type Assoc: ?Sized;
+}
+
+
+struct Leaf;
+struct Wrapper<U: ?Sized>(U);
+struct Rigid;
+
+impl<U: ?Sized> WithAssoc<U> for Leaf {
+    type Assoc = U;
+}
+
+
+impl<Ur: ?Sized> WithAssoc<Wrapper<Ur>> for Rigid
+where
+    Leaf: WithAssoc<Ur>,
+{
+    type Assoc = <<Leaf as WithAssoc<Ur>>::Assoc as Id>::Assoc;
+}
+
+fn bound<T: ?Sized, U: ?Sized, V: ?Sized>()
+where
+    T: WithAssoc<U, Assoc = V>,
+{
+}
+
+fn main() {
+    bound::<<Rigid as IdHigherRankedBound>::Assoc, <Wrapper<Leaf> as Id>::Assoc, _>()
+}

tests/ui/traits/new-solver/generalize/generalize-proj-new-universe-index-2.stderr

@@ -0,0 +1,9 @@
+error[E0282]: type annotations needed
+  --> $DIR/generalize-proj-new-universe-index-2.rs:74:5
+   |
+LL |     bound::<<Rigid as IdHigherRankedBound>::Assoc, <Wrapper<Leaf> as Id>::Assoc, _>()
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type of the type parameter `V` declared on the function `bound`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.