impl SessionDiagnostic for LayoutError and Spanned<T>

Author: ellishg

compiler/rustc_codegen_gcc/src/context.rs

@@ -13,7 +13,7 @@ use rustc_middle::mir::mono::CodegenUnit;
 use rustc_middle::ty::{self, Instance, ParamEnv, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_middle::ty::layout::{FnAbiError, FnAbiOfHelpers, FnAbiRequest, HasParamEnv, HasTyCtxt, LayoutError, TyAndLayout, LayoutOfHelpers};
 use rustc_session::Session;
-use rustc_span::Span;
+use rustc_span::{Span, source_map::respan};
 use rustc_target::abi::{call::FnAbi, HasDataLayout, PointeeInfo, Size, TargetDataLayout, VariantIdx};
 use rustc_target::spec::{HasTargetSpec, Target, TlsModel};
 
@@ -478,6 +478,23 @@ impl<'gcc, 'tcx> LayoutOfHelpers<'tcx> for CodegenCx<'gcc, 'tcx> {
     #[inline]
     fn handle_layout_err(&self, err: LayoutError<'tcx>, span: Span, ty: Ty<'tcx>) -> ! {
         if let LayoutError::SizeOverflow(_) = err {
+            let _ = respan(span, err);
+            //             error: lifetime may not live long enough
+            //    --> src/context.rs:483:13
+            //     |
+            // 475 | impl<'gcc, 'tcx> LayoutOfHelpers<'tcx> for CodegenCx<'gcc, 'tcx> {
+            //     |      ----  ---- lifetime `'tcx` defined here
+            //     |      |
+            //     |      lifetime `'gcc` defined here
+            // ...
+            // 483 |             self.sess().emit_fatal(respan(span, err))
+            //     |             ^^^^^^^^^^^ argument requires that `'gcc` must outlive `'tcx`
+            //     |
+            //     = help: consider adding the following bound: `'gcc: 'tcx`
+            //     = note: requirement occurs because of the type `CodegenCx<'_, '_>`, which makes the generic argument `'_` invariant
+            //     = note: the struct `CodegenCx<'gcc, 'tcx>` is invariant over the parameter `'gcc`
+            //     = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+            // self.sess().emit_fatal(respan(span, err))
             self.sess().emit_fatal(LayoutSizeOverflow { span, error: err.to_string() })
         } else {
             span_bug!(span, "failed to get layout for `{}`: {}", ty, err)

compiler/rustc_middle/src/ty/layout.rs

@@ -7,12 +7,15 @@ use crate::ty::{
 };
 use rustc_ast as ast;
 use rustc_attr as attr;
+use rustc_errors::Handler;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_index::bit_set::BitSet;
 use rustc_index::vec::{Idx, IndexVec};
-use rustc_session::{config::OptLevel, DataTypeKind, FieldInfo, SizeKind, VariantInfo};
+use rustc_session::{
+    config::OptLevel, DataTypeKind, FieldInfo, SessionDiagnostic, SizeKind, VariantInfo,
+};
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::call::{
@@ -206,6 +209,12 @@ pub enum LayoutError<'tcx> {
     NormalizationFailure(Ty<'tcx>, NormalizationError<'tcx>),
 }
 
+impl<'a> SessionDiagnostic<'a, !> for LayoutError<'a> {
+    fn into_diagnostic(self, handler: &'a Handler) -> rustc_errors::DiagnosticBuilder<'a, !> {
+        handler.struct_fatal(self.to_string())
+    }
+}
+
 impl<'tcx> fmt::Display for LayoutError<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {

compiler/rustc_session/src/session.rs

@@ -33,7 +33,7 @@ use rustc_errors::{
 use rustc_macros::HashStable_Generic;
 pub use rustc_span::def_id::StableCrateId;
 use rustc_span::edition::Edition;
-use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMap, Span};
+use rustc_span::source_map::{FileLoader, RealFileLoader, SourceMap, Span, Spanned};
 use rustc_span::{sym, SourceFileHashAlgorithm, Symbol};
 use rustc_target::asm::InlineAsmArch;
 use rustc_target::spec::{CodeModel, PanicStrategy, RelocModel, RelroLevel};
@@ -223,6 +223,27 @@ pub struct PerfStats {
     pub normalize_projection_ty: AtomicUsize,
 }
 
+/// Trait implemented by error types. This should not be implemented manually. Instead, use
+/// `#[derive(SessionDiagnostic)]` -- see [rustc_macros::SessionDiagnostic].
+#[rustc_diagnostic_item = "SessionDiagnostic"]
+pub trait SessionDiagnostic<'a, T: EmissionGuarantee = ErrorGuaranteed> {
+    /// Write out as a diagnostic out of `Handler`.
+    #[must_use]
+    fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, T>;
+}
+
+impl<'a, T, E> SessionDiagnostic<'a, E> for Spanned<T>
+where
+    T: SessionDiagnostic<'a, E>,
+    E: EmissionGuarantee,
+{
+    fn into_diagnostic(self, handler: &'a Handler) -> rustc_errors::DiagnosticBuilder<'a, E> {
+        let mut diag = self.node.into_diagnostic(handler);
+        diag.set_span(self.span);
+        diag
+    }
+}
+
 impl Session {
     pub fn miri_unleashed_feature(&self, span: Span, feature_gate: Option<Symbol>) {
         self.miri_unleashed_features.lock().push((span, feature_gate));