Remove some more usages of guess_head_span

compiler/rustc_infer/src/traits/error_reporting/mod.rs

@@ -18,20 +18,22 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         trait_item_def_id: DefId,
         requirement: &dyn fmt::Display,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let msg = "impl has stricter requirements than trait";
-        let sp = self.tcx.sess.source_map().guess_head_span(error_span);
+        let mut err = struct_span_err!(
+            self.tcx.sess,
+            error_span,
+            E0276,
+            "impl has stricter requirements than trait"
+        );
 
-        let mut err = struct_span_err!(self.tcx.sess, sp, E0276, "{}", msg);
-
-        if trait_item_def_id.is_local() {
+        if let Some(span) = self.tcx.hir().span_if_local(trait_item_def_id) {
             let item_name = self.tcx.item_name(impl_item_def_id.to_def_id());
             err.span_label(
-                self.tcx.def_span(trait_item_def_id),
+                span,
                 format!("definition of `{}` from trait", item_name),
             );
         }
 
-        err.span_label(sp, format!("impl has extra requirement {}", requirement));
+        err.span_label(error_span, format!("impl has extra requirement {}", requirement));
 
         err
     }
@@ -48,7 +50,6 @@ pub fn report_object_safety_error<'tcx>(
         hir::Node::Item(item) => Some(item.ident.span),
         _ => None,
     });
-    let span = tcx.sess.source_map().guess_head_span(span);
     let mut err = struct_span_err!(
         tcx.sess,
         span,

compiler/rustc_lint/src/context.rs

@@ -694,9 +694,8 @@ pub trait LintContext: Sized {
                     }
 
                     if let Some(span) = in_test_module {
-                        let def_span = self.sess().source_map().guess_head_span(span);
                         db.span_help(
-                            span.shrink_to_lo().to(def_span),
+                            self.sess().source_map().guess_head_span(span),
                             "consider adding a `#[cfg(test)]` to the containing module",
                         );
                     }

compiler/rustc_middle/src/traits/mod.rs

@@ -139,13 +139,8 @@ impl<'tcx> ObligationCause<'tcx> {
         ObligationCause { span, body_id: hir::CRATE_HIR_ID, code: Default::default() }
     }
 
-    pub fn span(&self, tcx: TyCtxt<'tcx>) -> Span {
+    pub fn span(&self, _tcx: TyCtxt<'tcx>) -> Span {
         match *self.code() {
-            ObligationCauseCode::CompareImplMethodObligation { .. }
-            | ObligationCauseCode::MainFunctionType
-            | ObligationCauseCode::StartFunctionType => {
-                tcx.sess.source_map().guess_head_span(self.span)
-            }
             ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
                 arm_span,
                 ..

compiler/rustc_privacy/src/lib.rs

@@ -1759,8 +1759,7 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
                 || self.tcx.resolutions(()).has_pub_restricted
             {
                 let descr = descr.to_string();
-                let vis_span =
-                    self.tcx.sess.source_map().guess_head_span(self.tcx.def_span(def_id));
+                let vis_span = self.tcx.def_span(def_id);
                 if kind == "trait" {
                     self.tcx.sess.emit_err(InPublicInterfaceTraits {
                         span,

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -953,7 +953,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
                 let found_span = found_did
                     .and_then(|did| self.tcx.hir().span_if_local(did))
-                    .map(|sp| self.tcx.sess.source_map().guess_head_span(sp)); // the sp could be an fn def
+                    .map(|sp| self.tcx.sess.source_map().guess_head_span(sp)); // the sp could be a closure
 
                 if self.reported_closure_mismatch.borrow().contains(&(span, found_span)) {
                     // We check closures twice, with obligations flowing in different directions,
@@ -1089,7 +1089,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 kind: hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, .. }),
                 ..
             }) => (
-                sm.guess_head_span(fn_decl_span),
+                fn_decl_span,
                 hir.body(body)
                     .params
                     .iter()

src/test/ui/wf/wf-unsafe-trait-obj-match.stderr

@@ -31,8 +31,12 @@ LL | trait Trait: Sized {}
 error[E0038]: the trait `Trait` cannot be made into an object
   --> $DIR/wf-unsafe-trait-obj-match.rs:25:25
    |
-LL |     let t: &dyn Trait = match opt() {
-   |                         ^^^^^^^^^^^ `Trait` cannot be made into an object
+LL |       let t: &dyn Trait = match opt() {
+   |  _________________________^
+LL | |         Some(()) => &S,
+LL | |         None => &R,
+LL | |     };
+   | |_____^ `Trait` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/wf-unsafe-trait-obj-match.rs:6:14