Auto merge of #76931 - oli-obk:const_prop_inline_lint_madness, r=wesleywiser

Properly handle lint spans after MIR inlining

The first commit shows what happens when we apply mir inlining and then cause lints on the inlined MIR.
The second commit fixes that.

r? `@wesleywiser`

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};
@@ -471,6 +472,8 @@ 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
@@ -682,6 +685,8 @@ 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> {
@@ -726,6 +731,14 @@ 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();