Auto merge of rust-lang#135059 - matthiaskrgr:rollup-0ka9o3h, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - rust-lang#131729 (Make the `test` cfg a userspace check-cfg)
 - rust-lang#134241 (more concrete source url of std docs [V2])
 - rust-lang#135042 (taint fcx on selection errors during unsizing)
 - rust-lang#135049 (Remove unused fields from RepeatElementCopy obligation)

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

Author: bors

compiler/rustc_hir_typeck/src/coercion.rs

@@ -666,7 +666,12 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
                 // Dyn-compatibility violations or miscellaneous.
                 Err(err) => {
-                    self.err_ctxt().report_selection_error(obligation.clone(), &obligation, &err);
+                    let guar = self.err_ctxt().report_selection_error(
+                        obligation.clone(),
+                        &obligation,
+                        &err,
+                    );
+                    self.fcx.set_tainted_by_errors(guar);
                     // Treat this like an obligation and follow through
                     // with the unsizing - the lack of a coercion should
                     // be silent, as it causes a type mismatch later.

compiler/rustc_hir_typeck/src/expr.rs

@@ -1907,21 +1907,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         let lang_item = self.tcx.require_lang_item(LangItem::Copy, None);
-        let code = traits::ObligationCauseCode::RepeatElementCopy {
-            is_constable,
-            elt_type: element_ty,
-            elt_span: element.span,
-            elt_stmt_span: self
-                .tcx
-                .hir()
-                .parent_iter(element.hir_id)
-                .find_map(|(_, node)| match node {
-                    hir::Node::Item(it) => Some(it.span),
-                    hir::Node::Stmt(stmt) => Some(stmt.span),
-                    _ => None,
-                })
-                .expect("array repeat expressions must be inside an item or statement"),
-        };
+        let code =
+            traits::ObligationCauseCode::RepeatElementCopy { is_constable, elt_span: element.span };
         self.require_type_meets(element_ty, element.span, code, lang_item);
     }
 

compiler/rustc_middle/src/traits/mod.rs

@@ -247,11 +247,11 @@ pub enum ObligationCauseCode<'tcx> {
         /// If element is a `const fn` or const ctor we display a help message suggesting
         /// to move it to a new `const` item while saying that `T` doesn't implement `Copy`.
         is_constable: IsConstable,
-        elt_type: Ty<'tcx>,
+
+        /// Span of the repeat element.
+        ///
+        /// This is used to suggest wrapping it in a `const { ... }` block.
         elt_span: Span,
-        /// Span of the statement/item in which the repeat expression occurs. We can use this to
-        /// place a `const` declaration before it
-        elt_stmt_span: Span,
     },
 
     /// Types of fields (other than the last, except for packed structs) in a struct must be sized.

compiler/rustc_session/src/config/cfg.rs

@@ -332,6 +332,11 @@ impl CheckCfg {
         // Note that symbols inserted conditionally in `default_configuration`
         // are inserted unconditionally here.
         //
+        // One exception is the `test` cfg which is consider to be a "user-space"
+        // cfg, despite being also set by in `default_configuration` above.
+        // It allows the build system to "deny" using the config by not marking it
+        // as expected (e.g. `lib.test = false` for Cargo).
+        //
         // When adding a new config here you should also update
         // `tests/ui/check-cfg/well-known-values.rs` (in order to test the
         // expected values of the new config) and bless the all directory.
@@ -453,8 +458,6 @@ impl CheckCfg {
 
         ins!(sym::target_thread_local, no_values);
 
-        ins!(sym::test, no_values);
-
         ins!(sym::ub_checks, no_values);
 
         ins!(sym::unix, no_values);

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -2966,12 +2966,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     "required for the cast from `{source}` to `{target}`",
                 )));
             }
-            ObligationCauseCode::RepeatElementCopy {
-                is_constable,
-                elt_type: _,
-                elt_span,
-                elt_stmt_span: _,
-            } => {
+            ObligationCauseCode::RepeatElementCopy { is_constable, elt_span } => {
                 err.note(
                     "the `Copy` trait is required because this value will be copied for each element of the array",
                 );

library/std/src/lib.rs

@@ -89,7 +89,7 @@
 //! Check out the Rust contribution guidelines [here](
 //! https://rustc-dev-guide.rust-lang.org/contributing.html#writing-documentation).
 //! The source for this documentation can be found on
-//! [GitHub](https://github.com/rust-lang/rust).
+//! [GitHub](https://github.com/rust-lang/rust) in the 'library/std/' directory.
 //! To contribute changes, make sure you read the guidelines first, then submit
 //! pull-requests for your suggested changes.
 //!

src/bootstrap/src/core/builder/cargo.rs

@@ -624,6 +624,8 @@ impl Builder<'_> {
         // get warnings about it being unexpected.
         hostflags.arg("-Zunstable-options");
         hostflags.arg("--check-cfg=cfg(bootstrap)");
+        // #[cfg(bootstrap)] as we are transition `test` to userspace cfg
+        hostflags.arg("--check-cfg=cfg(test)");
 
         // FIXME: It might be better to use the same value for both `RUSTFLAGS` and `RUSTDOCFLAGS`,
         // but this breaks CI. At the very least, stage0 `rustdoc` needs `--cfg bootstrap`. See

src/bootstrap/src/lib.rs

@@ -77,6 +77,8 @@ const LLD_FILE_NAMES: &[&str] = &["ld.lld", "ld64.lld", "lld-link", "wasm-ld"];
 #[allow(clippy::type_complexity)] // It's fine for hard-coded list and type is explained above.
 const EXTRA_CHECK_CFGS: &[(Option<Mode>, &str, Option<&[&'static str]>)] = &[
     (None, "bootstrap", None),
+    // #[cfg(bootstrap)] to be removed when Cargo is updated
+    (None, "test", None),
     (Some(Mode::Rustc), "llvm_enzyme", None),
     (Some(Mode::Codegen), "llvm_enzyme", None),
     (Some(Mode::ToolRustc), "llvm_enzyme", None),

src/doc/rustc/src/check-cfg.md

@@ -99,7 +99,7 @@ the need to specify them manually.
 Well known names and values are implicitly added as long as at least one `--check-cfg` argument
 is present.
 
-As of `2024-08-20T`, the list of known names is as follows:
+As of `2025-01-02T`, the list of known names is as follows:
 
 <!--- See CheckCfg::fill_well_known in compiler/rustc_session/src/config.rs -->
 
@@ -130,11 +130,13 @@ As of `2024-08-20T`, the list of known names is as follows:
  - `target_pointer_width`
  - `target_thread_local`
  - `target_vendor`
- - `test`
  - `ub_checks`
  - `unix`
  - `windows`
 
+> Starting with CURRENT_RUSTC_VERSION, the `test` cfg is consider to be a "userspace" config
+> despite being also set by `rustc` and should be managed by the build-system it-self.
+
 Like with `values(any())`, well known names checking can be disabled by passing `cfg(any())`
 as argument to `--check-cfg`.
 

src/tools/compiletest/src/runtest.rs

@@ -506,8 +506,9 @@ impl<'test> TestCx<'test> {
             // Generate `cfg(FALSE, REV1, ..., REVN)` (for all possible revisions)
             //
             // For compatibility reason we consider the `FALSE` cfg to be expected
-            // since it is extensively used in the testsuite.
-            check_cfg.push_str("cfg(FALSE");
+            // since it is extensively used in the testsuite, as well as the `test`
+            // cfg since we have tests that uses it.
+            check_cfg.push_str("cfg(test,FALSE");
             for revision in &self.props.revisions {
                 check_cfg.push(',');
                 check_cfg.push_str(&normalize_revision(revision));