expose span to M::assert_panic, and provide helper to turn that into CallerLocation

Author: RalfJung

src/librustc_mir/const_eval.rs

@@ -397,6 +397,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
 
     fn assert_panic(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        _span: Span,
         msg: &AssertMessage<'tcx>,
         _unwind: Option<mir::BasicBlock>,
     ) -> InterpResult<'tcx> {

src/librustc_mir/interpret/intrinsics.rs

@@ -110,13 +110,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         match intrinsic_name {
             "caller_location" => {
-                let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
-                let caller = self.tcx.sess.source_map().lookup_char_pos(topmost.lo());
-                let location = self.alloc_caller_location(
-                    Symbol::intern(&caller.file.name.to_string()),
-                    caller.line as u32,
-                    caller.col_display as u32 + 1,
-                )?;
+                let location = self.alloc_caller_location_for_span(span)?;
                 self.write_scalar(location.ptr, dest)?;
             }
 

src/librustc_mir/interpret/intrinsics/caller_location.rs

@@ -2,12 +2,12 @@ use rustc::middle::lang_items::PanicLocationLangItem;
 use rustc::mir::interpret::{Pointer, PointerArithmetic, Scalar};
 use rustc::ty::subst::Subst;
 use rustc_target::abi::{LayoutOf, Size};
-use syntax_pos::Symbol;
+use syntax_pos::{Symbol, Span};
 
 use crate::interpret::{MemoryKind, MPlaceTy, intrinsics::{InterpCx, InterpResult, Machine}};
 
 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
-    pub fn alloc_caller_location(
+    crate fn alloc_caller_location(
         &mut self,
         filename: Symbol,
         line: u32,
@@ -47,4 +47,17 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
         Ok(location)
     }
+
+    pub fn alloc_caller_location_for_span(
+        &mut self,
+        span: Span,
+    ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
+        let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
+        let caller = self.tcx.sess.source_map().lookup_char_pos(topmost.lo());
+        self.alloc_caller_location(
+            Symbol::intern(&caller.file.name.to_string()),
+            caller.line as u32,
+            caller.col_display as u32 + 1,
+        )
+    }
 }

src/librustc_mir/interpret/machine.rs

@@ -178,6 +178,7 @@ pub trait Machine<'mir, 'tcx>: Sized {
     /// Called to evaluate `Assert` MIR terminators that trigger a panic.
     fn assert_panic(
         ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        span: Span,
         msg: &AssertMessage<'tcx>,
         unwind: Option<mir::BasicBlock>,
     ) -> InterpResult<'tcx>;

src/librustc_mir/interpret/terminator.rs

@@ -122,7 +122,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 if expected == cond_val {
                     self.go_to_block(target);
                 } else {
-                    M::assert_panic(self, msg, cleanup)?;
+                    M::assert_panic(self, terminator.source_info.span, msg, cleanup)?;
                 }
             }
 

src/librustc_mir/transform/const_prop.rs

@@ -158,6 +158,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine {
 
     fn assert_panic(
         _ecx: &mut InterpCx<'mir, 'tcx, Self>,
+        _span: Span,
         _msg: &rustc::mir::interpret::AssertMessage<'tcx>,
         _unwind: Option<rustc::mir::BasicBlock>,
     ) -> InterpResult<'tcx> {