Use DUMMY_SP in less places

Fixes #845

src/base.rs

@@ -501,7 +501,7 @@ fn trans_stmt<'tcx>(
                     assert!(lval
                         .layout()
                         .ty
-                        .is_sized(fx.tcx.at(DUMMY_SP), ParamEnv::reveal_all()));
+                        .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all()));
                     let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
                     let val = CValue::const_val(fx, fx.tcx.types.usize, ty_size.into());
                     lval.write_cvalue(fx, val);

src/constant.rs

@@ -1,5 +1,7 @@
 use std::borrow::Cow;
 
+use syntax::source_map::DUMMY_SP;
+
 use rustc::mir::interpret::{
     read_target_uint, AllocId, Allocation, ConstValue, GlobalAlloc, InterpResult, Scalar,
 };

src/lib.rs

@@ -64,7 +64,7 @@ mod prelude {
     pub use std::convert::{TryFrom, TryInto};
 
     pub use syntax::ast::{FloatTy, IntTy, UintTy};
-    pub use syntax::source_map::{Pos, Span, DUMMY_SP};
+    pub use syntax::source_map::{Pos, Span};
 
     pub use rustc::bug;
     pub use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};