make the backtrace field of EvalError private

RalfJung · RalfJung · commit 625763fddd42 · 2019-06-07T13:48:51.000+02:00
This also makes sure people don't contruct these the wrong way
diff --git a/src/librustc/mir/interpret/error.rs b/src/librustc/mir/interpret/error.rs
@@ -182,7 +182,7 @@ pub fn struct_error<'a, 'gcx, 'tcx>(
 #[derive(Debug, Clone)]
 pub struct EvalError<'tcx> {
     pub kind: InterpError<'tcx, u64>,
-    pub backtrace: Option<Box<Backtrace>>,
+    backtrace: Option<Box<Backtrace>>,
 }
 
 impl<'tcx> EvalError<'tcx> {

Original file line number	Diff line number	Diff line change
`@@ -182,7 +182,7 @@ pub fn struct_error<'a, 'gcx, 'tcx>(`
`182`	`182`	`#[derive(Debug, Clone)]`
`183`	`183`	`pub struct EvalError<'tcx> {`
`184`	`184`	`pub kind: InterpError<'tcx, u64>,`
`185`		`- pub backtrace: Option<Box<Backtrace>>,`
	`185`	`+ backtrace: Option<Box<Backtrace>>,`
`186`	`186`	`}`
`187`	`187`
`188`	`188`	`impl<'tcx> EvalError<'tcx> {`