Show the inline stack of MIR lints that only occur after inlining

compiler/rustc_errors/src/emitter.rs

@@ -296,7 +296,7 @@ pub trait Emitter {
 
                     // Skip past non-macro entries, just in case there
                     // are some which do actually involve macros.
-                    ExpnKind::Desugaring(..) | ExpnKind::AstPass(..) => None,
+                    ExpnKind::Inlined | ExpnKind::Desugaring(..) | ExpnKind::AstPass(..) => None,
 
                     ExpnKind::Macro(macro_kind, _) => Some(macro_kind),
                 }
@@ -356,7 +356,9 @@ pub trait Emitter {
                     continue;
                 }
 
-                if always_backtrace {
+                if matches!(trace.kind, ExpnKind::Inlined) {
+                    new_labels.push((trace.call_site, "in the inlined copy of this".to_string()));
+                } else if always_backtrace {
                     new_labels.push((
                         trace.def_site,
                         format!(

compiler/rustc_middle/src/lint.rs

@@ -358,7 +358,9 @@ pub fn struct_lint_level<'s, 'd>(
 pub fn in_external_macro(sess: &Session, span: Span) -> bool {
     let expn_data = span.ctxt().outer_expn_data();
     match expn_data.kind {
-        ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop(_)) => false,
+        ExpnKind::Inlined | ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop(_)) => {
+            false
+        }
         ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => true, // well, it's "external"
         ExpnKind::Macro(MacroKind::Bang, _) => {
             // Dummy span for the `def_site` means it's an external macro.

compiler/rustc_mir/src/transform/inline.rs

@@ -8,6 +8,7 @@ use rustc_middle::mir::visit::*;
 use rustc_middle::mir::*;
 use rustc_middle::ty::subst::Subst;
 use rustc_middle::ty::{self, ConstKind, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
+use rustc_span::{hygiene::ExpnKind, ExpnData, Span};
 use rustc_target::spec::abi::Abi;
 
 use super::simplify::{remove_dead_blocks, CfgSimplifier};
@@ -488,6 +489,8 @@ impl Inliner<'tcx> {
                     cleanup_block: cleanup,
                     in_cleanup_block: false,
                     tcx: self.tcx,
+                    callsite_span: callsite.source_info.span,
+                    body_span: callee_body.span,
                 };
 
                 // Map all `Local`s, `SourceScope`s and `BasicBlock`s to new ones
@@ -699,6 +702,8 @@ struct Integrator<'a, 'tcx> {
     cleanup_block: Option<BasicBlock>,
     in_cleanup_block: bool,
     tcx: TyCtxt<'tcx>,
+    callsite_span: Span,
+    body_span: Span,
 }
 
 impl<'a, 'tcx> Integrator<'a, 'tcx> {
@@ -743,6 +748,14 @@ impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
         *scope = self.map_scope(*scope);
     }
 
+    fn visit_span(&mut self, span: &mut Span) {
+        // Make sure that all spans track the fact that they were inlined.
+        *span = self.callsite_span.fresh_expansion(ExpnData {
+            def_site: self.body_span,
+            ..ExpnData::default(ExpnKind::Inlined, *span, self.tcx.sess.edition(), None)
+        });
+    }
+
     fn visit_place(&mut self, place: &mut Place<'tcx>, context: PlaceContext, location: Location) {
         // If this is the `RETURN_PLACE`, we need to rebase any projections onto it.
         let dest_proj_len = self.destination.projection.len();

compiler/rustc_save_analysis/src/lib.rs

@@ -799,7 +799,9 @@ impl<'tcx> SaveContext<'tcx> {
 
             // These are not macros.
             // FIXME(eddyb) maybe there is a way to handle them usefully?
-            ExpnKind::Root | ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => return None,
+            ExpnKind::Inlined | ExpnKind::Root | ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => {
+                return None;
+            }
         };
 
         let callee_span = self.span_from_span(callee.def_site);

compiler/rustc_span/src/hygiene.rs

@@ -766,6 +766,8 @@ pub enum ExpnKind {
     AstPass(AstPass),
     /// Desugaring done by the compiler during HIR lowering.
     Desugaring(DesugaringKind),
+    /// MIR inlining
+    Inlined,
 }
 
 impl ExpnKind {
@@ -779,6 +781,7 @@ impl ExpnKind {
             },
             ExpnKind::AstPass(kind) => kind.descr().to_string(),
             ExpnKind::Desugaring(kind) => format!("desugaring of {}", kind.descr()),
+            ExpnKind::Inlined => "inlined source".to_string(),
         }
     }
 }