compute fn_sig span from body call_site, and use body ctxt, not root

Author: richkadel

compiler/rustc_mir/src/transform/coverage/spans.rs

@@ -11,7 +11,7 @@ use rustc_middle::mir::{
 use rustc_middle::ty::TyCtxt;
 
 use rustc_span::source_map::original_sp;
-use rustc_span::{BytePos, Span, SyntaxContext};
+use rustc_span::{BytePos, Span};
 
 use std::cmp::Ordering;
 
@@ -246,8 +246,8 @@ impl<'a, 'tcx> CoverageSpans<'a, 'tcx> {
     ) -> Vec<CoverageSpan> {
         let mut coverage_spans = CoverageSpans {
             mir_body,
-            fn_sig_span: fn_sig_span.with_ctxt(SyntaxContext::root()),
-            body_span: body_span.with_ctxt(SyntaxContext::root()),
+            fn_sig_span: fn_sig_source_span(fn_sig_span, body_span),
+            body_span,
             basic_coverage_blocks,
             sorted_spans_iter: None,
             refined_spans: Vec::with_capacity(basic_coverage_blocks.num_nodes() * 2),
@@ -731,8 +731,13 @@ pub(super) fn filtered_terminator_span(
     }
 }
 
+#[inline]
+fn fn_sig_source_span(fn_sig_span: Span, body_span: Span) -> Span {
+    original_sp(fn_sig_span, body_span).with_ctxt(body_span.ctxt())
+}
+
 #[inline]
 fn function_source_span(span: Span, body_span: Span) -> Span {
-    let span = original_sp(span, body_span).with_ctxt(SyntaxContext::root());
+    let span = original_sp(span, body_span).with_ctxt(body_span.ctxt());
     if body_span.contains(span) { span } else { body_span }
 }

src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.partial_eq.txt

@@ -2,7 +2,7 @@
     2|       |// structure of this test.
     3|       |
     4|      2|#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
-                       ^0            ^0         ^0  ^1          ^0
+                       ^0            ^0      ^0 ^0  ^1       ^1 ^0^0
   ------------------
   | Unexecuted instantiation: <partial_eq::Version as core::cmp::PartialEq>::ne
   ------------------