Rollup merge of #98657 - compiler-errors:rustc-const-eval-session-diagnostic-1, r=davidtwco

Migrate some diagnostics from `rustc_const_eval` to `SessionDiagnostic`

I'm still trying to get the hang of this, so it doesn't migrate _all_ of `rustc_const_eval`. Working on that later.

r? `@davidtwco`

Cargo.lock

@@ -3813,6 +3813,7 @@ dependencies = [
  "atty",
  "rustc_data_structures",
  "rustc_error_messages",
+ "rustc_hir",
  "rustc_lint_defs",
  "rustc_macros",
  "rustc_serialize",

compiler/rustc_const_eval/src/errors.rs

@@ -0,0 +1,89 @@
+use rustc_hir::ConstContext;
+use rustc_macros::SessionDiagnostic;
+use rustc_span::Span;
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::unstable_in_stable)]
+pub(crate) struct UnstableInStable {
+    pub gate: String,
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(
+        const_eval::unstable_sugg,
+        code = "#[rustc_const_unstable(feature = \"...\", issue = \"...\")]\n",
+        applicability = "has-placeholders"
+    )]
+    #[suggestion(
+        const_eval::bypass_sugg,
+        code = "#[rustc_allow_const_fn_unstable({gate})]\n",
+        applicability = "has-placeholders"
+    )]
+    pub attr_span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::thread_local_access, code = "E0625")]
+pub(crate) struct NonConstOpErr {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::static_access, code = "E0013")]
+#[help]
+pub(crate) struct StaticAccessErr {
+    #[primary_span]
+    pub span: Span,
+    pub kind: ConstContext,
+    #[note(const_eval::teach_note)]
+    #[help(const_eval::teach_help)]
+    pub teach: Option<()>,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::raw_ptr_to_int)]
+#[note]
+#[note(const_eval::note2)]
+pub(crate) struct RawPtrToIntErr {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::raw_ptr_comparison)]
+#[note]
+pub(crate) struct RawPtrComparisonErr {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::panic_non_str)]
+pub(crate) struct PanicNonStrErr {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::mut_deref, code = "E0658")]
+pub(crate) struct MutDerefErr {
+    #[primary_span]
+    pub span: Span,
+    pub kind: ConstContext,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::transient_mut_borrow, code = "E0658")]
+pub(crate) struct TransientMutBorrowErr {
+    #[primary_span]
+    pub span: Span,
+    pub kind: ConstContext,
+}
+
+#[derive(SessionDiagnostic)]
+#[error(const_eval::transient_mut_borrow_raw, code = "E0658")]
+pub(crate) struct TransientMutBorrowErrRaw {
+    #[primary_span]
+    pub span: Span,
+    pub kind: ConstContext,
+}

compiler/rustc_const_eval/src/lib.rs

@@ -31,6 +31,7 @@ extern crate tracing;
 extern crate rustc_middle;
 
 pub mod const_eval;
+mod errors;
 pub mod interpret;
 pub mod transform;
 pub mod util;

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -1,6 +1,6 @@
 //! The `Visitor` responsible for actually checking a `mir::Body` for invalid operations.
 
-use rustc_errors::{Applicability, Diagnostic, ErrorGuaranteed};
+use rustc_errors::{Diagnostic, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_index::bit_set::BitSet;
@@ -24,6 +24,7 @@ use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop, NeedsNonConstDro
 use super::resolver::FlowSensitiveAnalysis;
 use super::{ConstCx, Qualif};
 use crate::const_eval::is_unstable_const_fn;
+use crate::errors::UnstableInStable;
 
 type QualifResults<'mir, 'tcx, Q> =
     rustc_mir_dataflow::ResultsCursor<'mir, 'tcx, FlowSensitiveAnalysis<'mir, 'mir, 'tcx, Q>>;
@@ -1026,23 +1027,5 @@ fn is_int_bool_or_char(ty: Ty<'_>) -> bool {
 fn emit_unstable_in_stable_error(ccx: &ConstCx<'_, '_>, span: Span, gate: Symbol) {
     let attr_span = ccx.tcx.def_span(ccx.def_id()).shrink_to_lo();
 
-    ccx.tcx
-        .sess
-        .struct_span_err(
-            span,
-            &format!("const-stable function cannot use `#[feature({})]`", gate.as_str()),
-        )
-        .span_suggestion(
-            attr_span,
-            "if it is not part of the public API, make this function unstably const",
-            concat!(r#"#[rustc_const_unstable(feature = "...", issue = "...")]"#, '\n'),
-            Applicability::HasPlaceholders,
-        )
-        .span_suggestion(
-            attr_span,
-            "otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks",
-            format!("#[rustc_allow_const_fn_unstable({})]\n", gate),
-            Applicability::MaybeIncorrect,
-        )
-        .emit();
+    ccx.tcx.sess.emit_err(UnstableInStable { gate: gate.to_string(), span, attr_span });
 }

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -1,7 +1,9 @@
 //! Concrete error types for all operations which may be invalid in a certain const context.
 
 use hir::def_id::LocalDefId;
-use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{
+    error_code, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed,
+};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
@@ -20,6 +22,10 @@ use rustc_span::{BytePos, Pos, Span, Symbol};
 use rustc_trait_selection::traits::SelectionContext;
 
 use super::ConstCx;
+use crate::errors::{
+    MutDerefErr, NonConstOpErr, PanicNonStrErr, RawPtrComparisonErr, RawPtrToIntErr,
+    StaticAccessErr, TransientMutBorrowErr, TransientMutBorrowErrRaw,
+};
 use crate::util::{call_kind, CallDesugaringKind, CallKind};
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -590,17 +596,17 @@ impl<'tcx> NonConstOp<'tcx> for TransientMutBorrow {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let raw = match self.0 {
-            hir::BorrowKind::Raw => "raw ",
-            hir::BorrowKind::Ref => "",
-        };
-
-        feature_err(
-            &ccx.tcx.sess.parse_sess,
-            sym::const_mut_refs,
-            span,
-            &format!("{}mutable references are not allowed in {}s", raw, ccx.const_kind()),
-        )
+        let kind = ccx.const_kind();
+        match self.0 {
+            hir::BorrowKind::Raw => ccx
+                .tcx
+                .sess
+                .create_feature_err(TransientMutBorrowErrRaw { span, kind }, sym::const_mut_refs),
+            hir::BorrowKind::Ref => ccx
+                .tcx
+                .sess
+                .create_feature_err(TransientMutBorrowErr { span, kind }, sym::const_mut_refs),
+        }
     }
 }
 
@@ -621,12 +627,9 @@ impl<'tcx> NonConstOp<'tcx> for MutDeref {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        feature_err(
-            &ccx.tcx.sess.parse_sess,
-            sym::const_mut_refs,
-            span,
-            &format!("mutation through a reference is not allowed in {}s", ccx.const_kind()),
-        )
+        ccx.tcx
+            .sess
+            .create_feature_err(MutDerefErr { span, kind: ccx.const_kind() }, sym::const_mut_refs)
     }
 }
 
@@ -639,10 +642,7 @@ impl<'tcx> NonConstOp<'tcx> for PanicNonStr {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        ccx.tcx.sess.struct_span_err(
-            span,
-            "argument to `panic!()` in a const context must have type `&str`",
-        )
+        ccx.tcx.sess.create_err(PanicNonStrErr { span })
     }
 }
 
@@ -657,15 +657,7 @@ impl<'tcx> NonConstOp<'tcx> for RawPtrComparison {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let mut err = ccx
-            .tcx
-            .sess
-            .struct_span_err(span, "pointers cannot be reliably compared during const eval");
-        err.note(
-            "see issue #53020 <https://github.com/rust-lang/rust/issues/53020> \
-            for more information",
-        );
-        err
+        ccx.tcx.sess.create_err(RawPtrComparisonErr { span })
     }
 }
 
@@ -701,15 +693,7 @@ impl<'tcx> NonConstOp<'tcx> for RawPtrToIntCast {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let mut err = ccx
-            .tcx
-            .sess
-            .struct_span_err(span, "pointers cannot be cast to integers during const eval");
-        err.note("at compile-time, pointers do not have an integer value");
-        err.note(
-            "avoiding this restriction via `transmute`, `union`, or raw pointers leads to compile-time undefined behavior",
-        );
-        err
+        ccx.tcx.sess.create_err(RawPtrToIntErr { span })
     }
 }
 
@@ -730,24 +714,11 @@ impl<'tcx> NonConstOp<'tcx> for StaticAccess {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let mut err = struct_span_err!(
-            ccx.tcx.sess,
+        ccx.tcx.sess.create_err(StaticAccessErr {
             span,
-            E0013,
-            "{}s cannot refer to statics",
-            ccx.const_kind()
-        );
-        err.help(
-            "consider extracting the value of the `static` to a `const`, and referring to that",
-        );
-        if ccx.tcx.sess.teach(&err.get_code().unwrap()) {
-            err.note(
-                "`static` and `const` variables can refer to other `const` variables. \
-                    A `const` variable, however, cannot refer to a `static` variable.",
-            );
-            err.help("To fix this, the value can be extracted to a `const` and then used.");
-        }
-        err
+            kind: ccx.const_kind(),
+            teach: ccx.tcx.sess.teach(&error_code!(E0013)).then_some(()),
+        })
     }
 }
 
@@ -760,13 +731,7 @@ impl<'tcx> NonConstOp<'tcx> for ThreadLocalAccess {
         ccx: &ConstCx<'_, 'tcx>,
         span: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        struct_span_err!(
-            ccx.tcx.sess,
-            span,
-            E0625,
-            "thread-local statics cannot be \
-            accessed at compile-time"
-        )
+        ccx.tcx.sess.create_err(NonConstOpErr { span })
     }
 }
 

compiler/rustc_error_messages/locales/en-US/builtin_macros.ftl

@@ -1,5 +1,5 @@
-builtin_macros-requires-cfg-pattern =
+builtin-macros-requires-cfg-pattern =
     macro requires a cfg-pattern as an argument
     .label = cfg-pattern required
 
-builtin_macros-expected-one-cfg-pattern = expected 1 cfg-pattern
+builtin-macros-expected-one-cfg-pattern = expected 1 cfg-pattern

compiler/rustc_error_messages/locales/en-US/const_eval.ftl

@@ -0,0 +1,31 @@
+const-eval-unstable-in-stable =
+    const-stable function cannot use `#[feature({$gate})]`
+    .unstable-sugg = if it is not part of the public API, make this function unstably const
+    .bypass-sugg = otherwise `#[rustc_allow_const_fn_unstable]` can be used to bypass stability checks
+
+const-eval-thread-local-access =
+    thread-local statics cannot be accessed at compile-time
+
+const-eval-static-access =
+    {$kind}s cannot refer to statics
+    .help = consider extracting the value of the `static` to a `const`, and referring to that
+    .teach-note = `static` and `const` variables can refer to other `const` variables. A `const` variable, however, cannot refer to a `static` variable.
+    .teach-help = To fix this, the value can be extracted to a `const` and then used.
+
+const-eval-raw-ptr-to-int =
+    pointers cannot be cast to integers during const eval
+    .note = at compile-time, pointers do not have an integer value
+    .note2 = avoiding this restriction via `transmute`, `union`, or raw pointers leads to compile-time undefined behavior
+
+const-eval-raw-ptr-comparison =
+    pointers cannot be reliably compared during const eval
+    .note = see issue #53020 <https://github.com/rust-lang/rust/issues/53020> for more information
+
+const-eval-panic-non-str = argument to `panic!()` in a const context must have type `&str`
+
+const-eval-mut-deref =
+    mutation through a reference is not allowed in {$kind}s
+
+const-eval-transient-mut-borrow = mutable references are not allowed in {$kind}s
+
+const-eval-transient-mut-borrow-raw = raw mutable references are not allowed in {$kind}s

compiler/rustc_error_messages/src/lib.rs

@@ -37,6 +37,7 @@ fluent_messages! {
     parser => "../locales/en-US/parser.ftl",
     privacy => "../locales/en-US/privacy.ftl",
     typeck => "../locales/en-US/typeck.ftl",
+    const_eval => "../locales/en-US/const_eval.ftl",
 }
 
 pub use fluent_generated::{self as fluent, DEFAULT_LOCALE_RESOURCES};

compiler/rustc_errors/Cargo.toml

@@ -13,6 +13,7 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_hir = { path = "../rustc_hir" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
 unicode-width = "0.1.4"
 atty = "0.2"

compiler/rustc_errors/src/diagnostic.rs

@@ -5,6 +5,7 @@ use crate::{
 };
 use rustc_data_structures::stable_map::FxHashMap;
 use rustc_error_messages::FluentValue;
+use rustc_hir as hir;
 use rustc_lint_defs::{Applicability, LintExpectationId};
 use rustc_span::edition::LATEST_STABLE_EDITION;
 use rustc_span::symbol::{Ident, Symbol};
@@ -160,6 +161,16 @@ impl<'source> Into<FluentValue<'source>> for DiagnosticArgValue<'source> {
     }
 }
 
+impl IntoDiagnosticArg for hir::ConstContext {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Borrowed(match self {
+            hir::ConstContext::ConstFn => "constant function",
+            hir::ConstContext::Static(_) => "static",
+            hir::ConstContext::Const => "constant",
+        }))
+    }
+}
+
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
 /// `#[derive(SessionSubdiagnostic)]` -- see [rustc_macros::SessionSubdiagnostic].
 #[rustc_diagnostic_item = "AddSubdiagnostic"]

compiler/rustc_hir/src/hir.rs

@@ -1595,6 +1595,9 @@ impl fmt::Display for ConstContext {
     }
 }
 
+// NOTE: `IntoDiagnosticArg` impl for `ConstContext` lives in `rustc_errors`
+// due to a cyclical dependency between hir that crate.
+
 /// A literal.
 pub type Lit = Spanned<LitKind>;
 

compiler/rustc_macros/src/diagnostics/fluent.rs

@@ -189,9 +189,13 @@ pub(crate) fn fluent_messages(input: proc_macro::TokenStream) -> proc_macro::Tok
             if let Entry::Message(Message { id: Identifier { name }, attributes, .. }) = entry {
                 let _ = previous_defns.entry(name.to_string()).or_insert(ident_span);
 
-                // `typeck-foo-bar` => `foo_bar`
+                // `typeck-foo-bar` => `foo_bar` (in `typeck.ftl`)
+                // `const-eval-baz` => `baz` (in `const_eval.ftl`)
                 let snake_name = Ident::new(
-                    &name.replace(&format!("{}-", res.ident), "").replace("-", "_"),
+                    // FIXME: should probably trim prefix, not replace all occurrences
+                    &name
+                        .replace(&format!("{}-", res.ident).replace("_", "-"), "")
+                        .replace("-", "_"),
                     span,
                 );
                 constants.extend(quote! {

compiler/rustc_session/src/session.rs

@@ -2,7 +2,7 @@ use crate::cgu_reuse_tracker::CguReuseTracker;
 use crate::code_stats::CodeStats;
 pub use crate::code_stats::{DataTypeKind, FieldInfo, SizeKind, VariantInfo};
 use crate::config::{self, CrateType, OutputType, SwitchWithOptPath};
-use crate::parse::ParseSess;
+use crate::parse::{add_feature_diagnostics, ParseSess};
 use crate::search_paths::{PathKind, SearchPath};
 use crate::{filesearch, lint};
 
@@ -458,6 +458,15 @@ impl Session {
     ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
         self.parse_sess.create_err(err)
     }
+    pub fn create_feature_err<'a>(
+        &'a self,
+        err: impl SessionDiagnostic<'a>,
+        feature: Symbol,
+    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+        let mut err = self.parse_sess.create_err(err);
+        add_feature_diagnostics(&mut err, &self.parse_sess, feature);
+        err
+    }
     pub fn emit_err<'a>(&'a self, err: impl SessionDiagnostic<'a>) -> ErrorGuaranteed {
         self.parse_sess.emit_err(err)
     }