Auto merge of rust-lang#114063 - matthiaskrgr:rollup-c90czu6, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#114008 (coverage: Obtain the `__llvm_covfun` section name outside a per-function loop)
 - rust-lang#114014 (builtin_macros: expect raw strings too)
 - rust-lang#114043 (docs(LazyLock): add example pass local LazyLock variable to struct)
 - rust-lang#114051 (Add regression test for invalid "unused const" in method)
 - rust-lang#114052 (Suggest `{Option,Result}::as_ref()` instead of `cloned()` in some cases)
 - rust-lang#114058 (Add help for crate arg when crate name is invalid)
 - rust-lang#114060 (abi: unsized field in union - assert to delay bug )

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

Author: bors

compiler/rustc_abi/src/layout.rs

@@ -763,7 +763,9 @@ pub trait LayoutCalculator {
         let mut size = Size::ZERO;
         let only_variant = &variants[FIRST_VARIANT];
         for field in only_variant {
-            assert!(field.0.is_sized());
+            if field.0.is_unsized() {
+                self.delay_bug("unsized field in union".to_string());
+            }
 
             align = align.max(field.align());
             max_repr_align = max_repr_align.max(field.max_repr_align());

compiler/rustc_abi/src/lib.rs

@@ -1345,7 +1345,6 @@ impl Abi {
 
     /// Discard validity range information and allow undef.
     pub fn to_union(&self) -> Self {
-        assert!(self.is_sized());
         match *self {
             Abi::Scalar(s) => Abi::Scalar(s.to_union()),
             Abi::ScalarPair(s1, s2) => Abi::ScalarPair(s1.to_union(), s2.to_union()),

compiler/rustc_borrowck/src/lib.rs

@@ -2306,11 +2306,10 @@ mod error {
 
         pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_, ErrorGuaranteed>) {
             if let None = self.tainted_by_errors {
-                self.tainted_by_errors = Some(
-                    self.tcx
-                        .sess
-                        .delay_span_bug(t.span.clone(), "diagnostic buffered but not emitted"),
-                )
+                self.tainted_by_errors = Some(self.tcx.sess.delay_span_bug(
+                    t.span.clone_ignoring_labels(),
+                    "diagnostic buffered but not emitted",
+                ))
             }
             t.buffer(&mut self.buffered);
         }

compiler/rustc_builtin_macros/messages.ftl

@@ -109,8 +109,8 @@ builtin_macros_derive_path_args_value = traits in `#[derive(...)]` don't accept
     .suggestion = remove the value
 
 builtin_macros_env_not_defined = environment variable `{$var}` not defined at compile time
-    .cargo = Cargo sets build script variables at run time. Use `std::env::var("{$var}")` instead
-    .other = use `std::env::var("{$var}")` to read the variable at run time
+    .cargo = Cargo sets build script variables at run time. Use `std::env::var({$var_expr})` instead
+    .custom = use `std::env::var({$var_expr})` to read the variable at run time
 
 builtin_macros_env_takes_args = `env!()` takes 1 or 2 arguments
 

compiler/rustc_builtin_macros/src/env.rs

@@ -4,7 +4,7 @@
 //
 
 use rustc_ast::tokenstream::TokenStream;
-use rustc_ast::{self as ast, GenericArg};
+use rustc_ast::{self as ast, AstDeref, GenericArg};
 use rustc_expand::base::{self, *};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
@@ -76,41 +76,46 @@ pub fn expand_env<'cx>(
         },
     };
 
-    let sp = cx.with_def_site_ctxt(sp);
+    let span = cx.with_def_site_ctxt(sp);
     let value = env::var(var.as_str()).ok().as_deref().map(Symbol::intern);
     cx.sess.parse_sess.env_depinfo.borrow_mut().insert((var, value));
     let e = match value {
         None => {
-            // Use the string literal in the code in the diagnostic to avoid confusing diagnostics,
-            // e.g. when the literal contains escape sequences.
             let ast::ExprKind::Lit(ast::token::Lit {
-                kind: ast::token::LitKind::Str,
-                symbol: original_var,
+                kind: ast::token::LitKind::Str | ast::token::LitKind::StrRaw(..),
+                symbol,
                 ..
             }) = &var_expr.kind
             else {
                 unreachable!("`expr_to_string` ensures this is a string lit")
             };
-            cx.emit_err(errors::EnvNotDefined {
-                span: sp,
-                msg: custom_msg,
-                var: *original_var,
-                help: custom_msg.is_none().then(|| help_for_missing_env_var(var.as_str())),
-            });
+
+            if let Some(msg_from_user) = custom_msg {
+                cx.emit_err(errors::EnvNotDefinedWithUserMessage { span, msg_from_user });
+            } else if is_cargo_env_var(var.as_str()) {
+                cx.emit_err(errors::EnvNotDefined::CargoEnvVar {
+                    span,
+                    var: *symbol,
+                    var_expr: var_expr.ast_deref(),
+                });
+            } else {
+                cx.emit_err(errors::EnvNotDefined::CustomEnvVar {
+                    span,
+                    var: *symbol,
+                    var_expr: var_expr.ast_deref(),
+                });
+            }
+
             return DummyResult::any(sp);
         }
         Some(value) => cx.expr_str(sp, value),
     };
     MacEager::expr(e)
 }
 
-fn help_for_missing_env_var(var: &str) -> errors::EnvNotDefinedHelp {
-    if var.starts_with("CARGO_")
+/// Returns `true` if an environment variable from `env!` is one used by Cargo.
+fn is_cargo_env_var(var: &str) -> bool {
+    var.starts_with("CARGO_")
         || var.starts_with("DEP_")
         || matches!(var, "OUT_DIR" | "OPT_LEVEL" | "PROFILE" | "HOST" | "TARGET")
-    {
-        errors::EnvNotDefinedHelp::CargoVar
-    } else {
-        errors::EnvNotDefinedHelp::Other
-    }
 }

compiler/rustc_builtin_macros/src/errors.rs

@@ -440,43 +440,43 @@ pub(crate) struct EnvTakesArgs {
     pub(crate) span: Span,
 }
 
-//#[derive(Diagnostic)]
-//#[diag(builtin_macros_env_not_defined)]
-pub(crate) struct EnvNotDefined {
+pub(crate) struct EnvNotDefinedWithUserMessage {
     pub(crate) span: Span,
-    pub(crate) msg: Option<Symbol>,
-    pub(crate) var: Symbol,
-    pub(crate) help: Option<EnvNotDefinedHelp>,
+    pub(crate) msg_from_user: Symbol,
 }
 
-// Hand-written implementation to support custom user messages
-impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for EnvNotDefined {
+// Hand-written implementation to support custom user messages.
+impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for EnvNotDefinedWithUserMessage {
     #[track_caller]
     fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, G> {
-        let mut diag = if let Some(msg) = self.msg {
-            #[expect(
-                rustc::untranslatable_diagnostic,
-                reason = "cannot translate user-provided messages"
-            )]
-            handler.struct_diagnostic(msg.to_string())
-        } else {
-            handler.struct_diagnostic(crate::fluent_generated::builtin_macros_env_not_defined)
-        };
-        diag.set_arg("var", self.var);
+        #[expect(
+            rustc::untranslatable_diagnostic,
+            reason = "cannot translate user-provided messages"
+        )]
+        let mut diag = handler.struct_diagnostic(self.msg_from_user.to_string());
         diag.set_span(self.span);
-        if let Some(help) = self.help {
-            diag.subdiagnostic(help);
-        }
         diag
     }
 }
 
-#[derive(Subdiagnostic)]
-pub(crate) enum EnvNotDefinedHelp {
+#[derive(Diagnostic)]
+pub(crate) enum EnvNotDefined<'a> {
+    #[diag(builtin_macros_env_not_defined)]
     #[help(builtin_macros_cargo)]
-    CargoVar,
-    #[help(builtin_macros_other)]
-    Other,
+    CargoEnvVar {
+        #[primary_span]
+        span: Span,
+        var: Symbol,
+        var_expr: &'a rustc_ast::Expr,
+    },
+    #[diag(builtin_macros_env_not_defined)]
+    #[help(builtin_macros_custom)]
+    CustomEnvVar {
+        #[primary_span]
+        span: Span,
+        var: Symbol,
+        var_expr: &'a rustc_ast::Expr,
+    },
 }
 
 #[derive(Diagnostic)]

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -100,9 +100,11 @@ pub fn finalize(cx: &CodegenCx<'_, '_>) {
     // Generate the LLVM IR representation of the coverage map and store it in a well-known global
     let cov_data_val = mapgen.generate_coverage_map(cx, version, filenames_size, filenames_val);
 
+    let covfun_section_name = coverageinfo::covfun_section_name(cx);
     for (mangled_function_name, source_hash, is_used, coverage_mapping_buffer) in function_data {
         save_function_record(
             cx,
+            &covfun_section_name,
             mangled_function_name,
             source_hash,
             filenames_ref,
@@ -228,6 +230,7 @@ impl CoverageMapGenerator {
 /// specific, well-known section and name.
 fn save_function_record(
     cx: &CodegenCx<'_, '_>,
+    covfun_section_name: &str,
     mangled_function_name: &str,
     source_hash: u64,
     filenames_ref: u64,
@@ -254,7 +257,13 @@ fn save_function_record(
         /*packed=*/ true,
     );
 
-    coverageinfo::save_func_record_to_mod(cx, func_name_hash, func_record_val, is_used);
+    coverageinfo::save_func_record_to_mod(
+        cx,
+        covfun_section_name,
+        func_name_hash,
+        func_record_val,
+        is_used,
+    );
 }
 
 /// When finalizing the coverage map, `FunctionCoverage` only has the `CodeRegion`s and counters for

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -408,6 +408,7 @@ pub(crate) fn save_cov_data_to_mod<'ll, 'tcx>(
 
 pub(crate) fn save_func_record_to_mod<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
+    covfun_section_name: &str,
     func_name_hash: u64,
     func_record_val: &'ll llvm::Value,
     is_used: bool,
@@ -423,20 +424,33 @@ pub(crate) fn save_func_record_to_mod<'ll, 'tcx>(
     let func_record_var_name =
         format!("__covrec_{:X}{}", func_name_hash, if is_used { "u" } else { "" });
     debug!("function record var name: {:?}", func_record_var_name);
-
-    let func_record_section_name = llvm::build_string(|s| unsafe {
-        llvm::LLVMRustCoverageWriteFuncSectionNameToString(cx.llmod, s);
-    })
-    .expect("Rust Coverage function record section name failed UTF-8 conversion");
-    debug!("function record section name: {:?}", func_record_section_name);
+    debug!("function record section name: {:?}", covfun_section_name);
 
     let llglobal = llvm::add_global(cx.llmod, cx.val_ty(func_record_val), &func_record_var_name);
     llvm::set_initializer(llglobal, func_record_val);
     llvm::set_global_constant(llglobal, true);
     llvm::set_linkage(llglobal, llvm::Linkage::LinkOnceODRLinkage);
     llvm::set_visibility(llglobal, llvm::Visibility::Hidden);
-    llvm::set_section(llglobal, &func_record_section_name);
+    llvm::set_section(llglobal, covfun_section_name);
     llvm::set_alignment(llglobal, VAR_ALIGN_BYTES);
     llvm::set_comdat(cx.llmod, llglobal, &func_record_var_name);
     cx.add_used_global(llglobal);
 }
+
+/// Returns the section name string to pass through to the linker when embedding
+/// per-function coverage information in the object file, according to the target
+/// platform's object file format.
+///
+/// LLVM's coverage tools read coverage mapping details from this section when
+/// producing coverage reports.
+///
+/// Typical values are:
+/// - `__llvm_covfun` on Linux
+/// - `__LLVM_COV,__llvm_covfun` on macOS (includes `__LLVM_COV,` segment prefix)
+/// - `.lcovfun$M` on Windows (includes `$M` sorting suffix)
+pub(crate) fn covfun_section_name(cx: &CodegenCx<'_, '_>) -> String {
+    llvm::build_string(|s| unsafe {
+        llvm::LLVMRustCoverageWriteFuncSectionNameToString(cx.llmod, s);
+    })
+    .expect("Rust Coverage function record section name failed UTF-8 conversion")
+}

compiler/rustc_error_messages/src/lib.rs

@@ -533,6 +533,14 @@ impl MultiSpan {
     pub fn has_span_labels(&self) -> bool {
         self.span_labels.iter().any(|(sp, _)| !sp.is_dummy())
     }
+
+    /// Clone this `MultiSpan` without keeping any of the span labels - sometimes a `MultiSpan` is
+    /// to be re-used in another diagnostic, but includes `span_labels` which have translated
+    /// messages. These translated messages would fail to translate without their diagnostic
+    /// arguments which are unlikely to be cloned alongside the `Span`.
+    pub fn clone_ignoring_labels(&self) -> Self {
+        Self { primary_spans: self.primary_spans.clone(), ..MultiSpan::new() }
+    }
 }
 
 impl From<Span> for MultiSpan {

compiler/rustc_errors/src/diagnostic_impls.rs

@@ -164,6 +164,12 @@ impl IntoDiagnosticArg for hir::ConstContext {
     }
 }
 
+impl IntoDiagnosticArg for ast::Expr {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Owned(pprust::expr_to_string(&self)))
+    }
+}
+
 impl IntoDiagnosticArg for ast::Path {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Str(Cow::Owned(pprust::path_to_string(&self)))

compiler/rustc_hir_typeck/src/demand.rs

@@ -53,7 +53,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             || self.suggest_no_capture_closure(err, expected, expr_ty)
             || self.suggest_boxing_when_appropriate(err, expr.span, expr.hir_id, expected, expr_ty)
             || self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected)
-            || self.suggest_copied_or_cloned(err, expr, expr_ty, expected)
+            || self.suggest_copied_cloned_or_as_ref(err, expr, expr_ty, expected, expected_ty_expr)
             || self.suggest_clone_for_ref(err, expr, expr_ty, expected)
             || self.suggest_into(err, expr, expr_ty, expected)
             || self.suggest_floating_point_literal(err, expr, expected)

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1085,12 +1085,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         false
     }
 
-    pub(crate) fn suggest_copied_or_cloned(
+    pub(crate) fn suggest_copied_cloned_or_as_ref(
         &self,
         diag: &mut Diagnostic,
         expr: &hir::Expr<'_>,
         expr_ty: Ty<'tcx>,
         expected_ty: Ty<'tcx>,
+        expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
     ) -> bool {
         let ty::Adt(adt_def, args) = expr_ty.kind() else {
             return false;
@@ -1102,7 +1103,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return false;
         }
 
-        let mut suggest_copied_or_cloned = || {
+        let mut suggest_copied_cloned_or_as_ref = || {
             let expr_inner_ty = args.type_at(0);
             let expected_inner_ty = expected_args.type_at(0);
             if let &ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind()
@@ -1119,6 +1120,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         Applicability::MachineApplicable,
                     );
                     return true;
+                } else if let Some(expected_ty_expr) = expected_ty_expr {
+                    diag.span_suggestion_verbose(
+                        expected_ty_expr.span.shrink_to_hi(),
+                        format!(
+                            "use `{def_path}::as_ref()` to convert `{expected_ty}` to `{expr_ty}`"
+                        ),
+                        ".as_ref()",
+                        Applicability::MachineApplicable,
+                    );
+                    return true;
                 } else if let Some(clone_did) = self.tcx.lang_items().clone_trait()
                     && rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions(
                         self,
@@ -1146,11 +1157,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Check that the error types are equal
             && self.can_eq(self.param_env, args.type_at(1), expected_args.type_at(1))
         {
-            return suggest_copied_or_cloned();
+            return suggest_copied_cloned_or_as_ref();
         } else if let Some(option_did) = self.tcx.get_diagnostic_item(sym::Option)
             && adt_def.did() == option_did
         {
-            return suggest_copied_or_cloned();
+            return suggest_copied_cloned_or_as_ref();
         }
 
         false

compiler/rustc_session/messages.ftl

@@ -45,6 +45,7 @@ session_int_literal_too_large = integer literal is too large
     .note = value exceeds limit of `{$limit}`
 
 session_invalid_character_in_create_name = invalid character `{$character}` in crate name: `{$crate_name}`
+session_invalid_character_in_create_name_help = you can either pass `--crate-name` on the command line or add `#![crate_name="…"]` to set the crate name
 
 session_invalid_float_literal_suffix = invalid suffix `{$suffix}` for float literal
     .label = invalid suffix `{$suffix}`

compiler/rustc_session/src/errors.rs

@@ -199,6 +199,14 @@ pub struct InvalidCharacterInCrateName {
     pub span: Option<Span>,
     pub character: char,
     pub crate_name: Symbol,
+    #[subdiagnostic]
+    pub crate_name_help: Option<InvalidCrateNameHelp>,
+}
+
+#[derive(Subdiagnostic)]
+pub enum InvalidCrateNameHelp {
+    #[help(session_invalid_character_in_create_name_help)]
+    AddCrateName,
 }
 
 #[derive(Subdiagnostic)]