Auto merge of rust-lang#118942 - GuillaumeGomez:rollup-n5vtatg, r=GuillaumeGomez

Rollup of 4 pull requests

Successful merges:

 - rust-lang#118770 (Fix cases where std accidentally relied on inline(never))
 - rust-lang#118910 ([rustdoc] Use Map instead of Object for source files and search index)
 - rust-lang#118914 (Unconditionally register alias-relate in projection goal)
 - rust-lang#118935 (interpret: extend comment on the inhabitedness check in downcast)

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

Author: bors

compiler/rustc_const_eval/src/interpret/projection.rs

@@ -208,6 +208,24 @@ where
         if layout.abi.is_uninhabited() {
             // `read_discriminant` should have excluded uninhabited variants... but ConstProp calls
             // us on dead code.
+            // In the future we might want to allow this to permit code like this:
+            // (this is a Rust/MIR pseudocode mix)
+            // ```
+            // enum Option2 {
+            //   Some(i32, !),
+            //   None,
+            // }
+            //
+            // fn panic() -> ! { panic!() }
+            //
+            // let x: Option2;
+            // x.Some.0 = 42;
+            // x.Some.1 = panic();
+            // SetDiscriminant(x, Some);
+            // ```
+            // However, for now we don't generate such MIR, and this check here *has* found real
+            // bugs (see https://github.com/rust-lang/rust/issues/115145), so we will keep rejecting
+            // it.
             throw_inval!(ConstPropNonsense)
         }
         // This cannot be `transmute` as variants *can* have a smaller size than the entire enum.

compiler/rustc_mir_transform/src/cross_crate_inline.rs

@@ -22,6 +22,18 @@ fn cross_crate_inlinable(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
         return false;
     }
 
+    // This just reproduces the logic from Instance::requires_inline.
+    match tcx.def_kind(def_id) {
+        DefKind::Ctor(..) | DefKind::Closure => return true,
+        DefKind::Fn | DefKind::AssocFn => {}
+        _ => return false,
+    }
+
+    // From this point on, it is valid to return true or false.
+    if tcx.sess.opts.unstable_opts.cross_crate_inline_threshold == InliningThreshold::Always {
+        return true;
+    }
+
     // Obey source annotations first; this is important because it means we can use
     // #[inline(never)] to force code generation.
     match codegen_fn_attrs.inline {
@@ -30,13 +42,6 @@ fn cross_crate_inlinable(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
         _ => {}
     }
 
-    // This just reproduces the logic from Instance::requires_inline.
-    match tcx.def_kind(def_id) {
-        DefKind::Ctor(..) | DefKind::Closure => return true,
-        DefKind::Fn | DefKind::AssocFn => {}
-        _ => return false,
-    }
-
     // Don't do any inference when incremental compilation is enabled; the additional inlining that
     // inference permits also creates more work for small edits.
     if tcx.sess.opts.incremental.is_some() {

compiler/rustc_monomorphize/src/collector.rs

@@ -176,6 +176,7 @@ use rustc_middle::mir::visit::Visitor as MirVisitor;
 use rustc_middle::mir::{self, Location};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCoercion};
+use rustc_middle::ty::layout::ValidityRequirement;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
     self, AssocKind, GenericParamDefKind, Instance, InstanceDef, Ty, TyCtxt, TypeFoldable,
@@ -923,6 +924,21 @@ fn visit_instance_use<'tcx>(
         return;
     }
 
+    // The intrinsics assert_inhabited, assert_zero_valid, and assert_mem_uninitialized_valid will
+    // be lowered in codegen to nothing or a call to panic_nounwind. So if we encounter any
+    // of those intrinsics, we need to include a mono item for panic_nounwind, else we may try to
+    // codegen a call to that function without generating code for the function itself.
+    if let ty::InstanceDef::Intrinsic(def_id) = instance.def {
+        let name = tcx.item_name(def_id);
+        if let Some(_requirement) = ValidityRequirement::from_intrinsic(name) {
+            let def_id = tcx.lang_items().get(LangItem::PanicNounwind).unwrap();
+            let panic_instance = Instance::mono(tcx, def_id);
+            if should_codegen_locally(tcx, &panic_instance) {
+                output.push(create_fn_mono_item(tcx, panic_instance, source));
+            }
+        }
+    }
+
     match instance.def {
         ty::InstanceDef::Virtual(..) | ty::InstanceDef::Intrinsic(_) => {
             if !is_direct_call {

compiler/rustc_monomorphize/src/partitioning.rs

@@ -212,11 +212,17 @@ where
     let cgu_name_cache = &mut FxHashMap::default();
 
     for mono_item in mono_items {
-        // Handle only root items directly here. Inlined items are handled at
-        // the bottom of the loop based on reachability.
+        // Handle only root (GloballyShared) items directly here. Inlined (LocalCopy) items
+        // are handled at the bottom of the loop based on reachability, with one exception.
+        // The #[lang = "start"] item is the program entrypoint, so there are no calls to it in MIR.
+        // So even if its mode is LocalCopy, we need to treat it like a root.
         match mono_item.instantiation_mode(cx.tcx) {
             InstantiationMode::GloballyShared { .. } => {}
-            InstantiationMode::LocalCopy => continue,
+            InstantiationMode::LocalCopy => {
+                if Some(mono_item.def_id()) != cx.tcx.lang_items().start_fn() {
+                    continue;
+                }
+            }
         }
 
         let characteristic_def_id = characteristic_def_id_of_mono_item(cx.tcx, mono_item);

compiler/rustc_trait_selection/src/solve/project_goals.rs

@@ -8,16 +8,28 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         &mut self,
         goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
     ) -> QueryResult<'tcx> {
-        match goal.predicate.term.unpack() {
-            ty::TermKind::Ty(term) => {
-                let alias = goal.predicate.projection_ty.to_ty(self.tcx());
-                self.eq(goal.param_env, alias, term)?;
-                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-            }
-            // FIXME(associated_const_equality): actually do something here.
-            ty::TermKind::Const(_) => {
-                self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
-            }
-        }
+        let tcx = self.tcx();
+        let projection_term = match goal.predicate.term.unpack() {
+            ty::TermKind::Ty(_) => goal.predicate.projection_ty.to_ty(tcx).into(),
+            ty::TermKind::Const(_) => ty::Const::new_unevaluated(
+                tcx,
+                ty::UnevaluatedConst::new(
+                    goal.predicate.projection_ty.def_id,
+                    goal.predicate.projection_ty.args,
+                ),
+                tcx.type_of(goal.predicate.projection_ty.def_id)
+                    .instantiate(tcx, goal.predicate.projection_ty.args),
+            )
+            .into(),
+        };
+        self.add_goal(goal.with(
+            tcx,
+            ty::PredicateKind::AliasRelate(
+                projection_term,
+                goal.predicate.term,
+                ty::AliasRelationDirection::Equate,
+            ),
+        ));
+        self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 }

library/std/src/rt.rs

@@ -155,7 +155,6 @@ fn lang_start_internal(
 }
 
 #[cfg(not(test))]
-#[inline(never)]
 #[lang = "start"]
 fn lang_start<T: crate::process::Termination + 'static>(
     main: fn() -> T,

src/librustdoc/html/render/search_index.rs

@@ -488,7 +488,7 @@ pub(crate) fn build_index<'tcx>(
 
     // Collect the index into a string
     format!(
-        r#""{}":{}"#,
+        r#"["{}",{}]"#,
         krate.name(tcx),
         serde_json::to_string(&CrateData {
             doc: crate_doc,

src/librustdoc/html/render/write_shared.rs

@@ -167,23 +167,24 @@ pub(super) fn write_shared(
         let mut krates = Vec::new();
 
         if path.exists() {
-            let prefix = format!("\"{krate}\"");
+            let prefix = format!("[\"{krate}\"");
             for line in BufReader::new(File::open(path)?).lines() {
                 let line = line?;
-                if !line.starts_with('"') {
+                if !line.starts_with("[\"") {
                     continue;
                 }
                 if line.starts_with(&prefix) {
                     continue;
                 }
-                if line.ends_with(",\\") {
+                if line.ends_with("],\\") {
                     ret.push(line[..line.len() - 2].to_string());
                 } else {
                     // Ends with "\\" (it's the case for the last added crate line)
                     ret.push(line[..line.len() - 1].to_string());
                 }
                 krates.push(
-                    line.split('"')
+                    line[1..] // We skip the `[` parent at the beginning of the line.
+                        .split('"')
                         .find(|s| !s.is_empty())
                         .map(|s| s.to_owned())
                         .unwrap_or_else(String::new),
@@ -285,7 +286,7 @@ pub(super) fn write_shared(
             let (mut all_sources, _krates) =
                 try_err!(collect_json(&dst, krate.name(cx.tcx()).as_str()), &dst);
             all_sources.push(format!(
-                r#""{}":{}"#,
+                r#"["{}",{}]"#,
                 &krate.name(cx.tcx()),
                 hierarchy
                     .to_json_string()
@@ -296,9 +297,9 @@ pub(super) fn write_shared(
                     .replace("\\\"", "\\\\\"")
             ));
             all_sources.sort();
-            let mut v = String::from("var srcIndex = JSON.parse('{\\\n");
+            let mut v = String::from("const srcIndex = new Map(JSON.parse('[\\\n");
             v.push_str(&all_sources.join(",\\\n"));
-            v.push_str("\\\n}');\ncreateSrcSidebar();\n");
+            v.push_str("\\\n]'));\ncreateSrcSidebar();\n");
             Ok(v.into_bytes())
         };
         write_invocation_specific("src-files.js", &make_sources)?;
@@ -316,11 +317,11 @@ pub(super) fn write_shared(
     // with rustdoc running in parallel.
     all_indexes.sort();
     write_invocation_specific("search-index.js", &|| {
-        let mut v = String::from("var searchIndex = JSON.parse('{\\\n");
+        let mut v = String::from("const searchIndex = new Map(JSON.parse('[\\\n");
         v.push_str(&all_indexes.join(",\\\n"));
         v.push_str(
             r#"\
-}');
+]'));
 if (typeof window !== 'undefined' && window.initSearch) {window.initSearch(searchIndex)};
 if (typeof exports !== 'undefined') {exports.searchIndex = searchIndex};
 "#,