Fix line numbers for MIR inlined code

`should_collapse_debuginfo` detects if the specified span is part of a
macro expansion however it does this by checking if the span is anything
other than a normal (non-expanded) kind, then the span sequence is
walked backwards to the root span.

This doesn't work when the MIR inliner inlines code as it creates spans
with expansion information set to `ExprKind::Inlined` and results in the
line number being attributed to the inline callsite rather than the
normal line number of the inlined code.

1 files changed, 7 insertions, 1 deletions

diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 91eef647713..ec5491116e8 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -558,7 +558,7 @@ impl Span {
         self.data_untracked().is_dummy()
     }
 
-    /// Returns `true` if this span comes from a macro or desugaring.
+    /// Returns `true` if this span comes from any kind of macro, desugaring or inlining.
     #[inline]
     pub fn from_expansion(self) -> bool {
         self.ctxt() != SyntaxContext::root()
@@ -571,6 +571,12 @@ impl Span {
         matches!(outer_expn.kind, ExpnKind::Macro(..)) && outer_expn.collapse_debuginfo
     }
 
+    /// Returns `true` if this span comes from MIR inlining.
+    pub fn is_inlined(self) -> bool {
+        let outer_expn = self.ctxt().outer_expn_data();
+        matches!(outer_expn.kind, ExpnKind::Inlined)
+    }
+
     /// Returns `true` if `span` originates in a derive-macro's expansion.
     pub fn in_derive_expansion(self) -> bool {
         matches!(self.ctxt().outer_expn_data().kind, ExpnKind::Macro(MacroKind::Derive, _))