better span for functions whose frame we push 'manually'

Author: RalfJung

src/eval.rs

@@ -221,12 +221,7 @@ pub fn eval_main<'tcx>(tcx: TyCtxt<'tcx>, main_id: DefId, config: MiriConfig) ->
             };
             e.print_backtrace();
             if let Some(frame) = ecx.stack().last() {
-                let block = &frame.body.basic_blocks()[frame.block.unwrap()];
-                let span = if frame.stmt < block.statements.len() {
-                    block.statements[frame.stmt].source_info.span
-                } else {
-                    block.terminator().source_info.span
-                };
+                let span = frame.current_source_info().unwrap().span;
 
                 let msg = format!("Miri evaluation error: {}", msg);
                 let mut err = ecx.tcx.sess.struct_span_err(span, msg.as_str());

src/helpers.rs

@@ -132,9 +132,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         // Push frame.
         let mir = this.load_mir(f.def, None)?;
+        let span = this.stack().last()
+            .and_then(Frame::current_source_info)
+            .map(|si| si.span)
+            .unwrap_or(DUMMY_SP);
         this.push_stack_frame(
             f,
-            DUMMY_SP, // There is no call site.
+            span,
             mir,
             dest,
             stack_pop,

src/shims/panic.rs

@@ -166,7 +166,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // Forward to `panic_bounds_check` lang item.
 
                 // First arg: Caller location.
-                let location = this.alloc_caller_location_for_span(span)?;
+                let location = this.alloc_caller_location_for_span(span);
                 // Second arg: index.
                 let index = this.read_scalar(this.eval_operand(index, None)?)?;
                 // Third arg: len.
@@ -190,7 +190,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let msg = this.allocate_str(msg, MiriMemoryKind::Static.into());
 
                 // Second arg: Caller location.
-                let location = this.alloc_caller_location_for_span(span)?;
+                let location = this.alloc_caller_location_for_span(span);
 
                 // Call the lang item.
                 let panic = this.tcx.lang_items().panic_fn().unwrap();