Ok(InferOk { obligations, value: () }) => {
self.register_predicates(obligations);
None
- },
+ }
Err(e) => {
Some(self.report_mismatched_types(cause, expected, actual, e))
}
// Checks that the type of `expr` can be coerced to `expected`.
//
- // NB: This code relies on `self.diverges` to be accurate. In
+ // NB: This code relies on `self.diverges` to be accurate. In
// particular, assignments to `!` will be permitted if the
// diverges flag is currently "always".
pub fn demand_coerce_diag(&self,
expected: Ty<'tcx>)
-> Option<String> {
match (&expected.sty, &checked_ty.sty) {
- (&ty::TyRef(_, _), &ty::TyRef(_, _)) => None,
+ (&ty::TyRef(_, exp), &ty::TyRef(_, check)) => match (&exp.ty.sty, &check.ty.sty) {
+ (&ty::TyStr, &ty::TyArray(arr, _)) |
+ (&ty::TyStr, &ty::TySlice(arr)) if arr == self.tcx.types.u8 => {
+ if let hir::ExprLit(_) = expr.node {
+ let sp = self.sess().codemap().call_span_if_macro(expr.span);
+ if let Ok(src) = self.tcx.sess.codemap().span_to_snippet(sp) {
+ return Some(format!("try `{}`", &src[1..]));
+ }
+ }
+ None
+ },
+ (&ty::TyArray(arr, _), &ty::TyStr) |
+ (&ty::TySlice(arr), &ty::TyStr) if arr == self.tcx.types.u8 => {
+ if let hir::ExprLit(_) = expr.node {
+ let sp = self.sess().codemap().call_span_if_macro(expr.span);
+ if let Ok(src) = self.tcx.sess.codemap().span_to_snippet(sp) {
+ return Some(format!("try `b{}`", src));
+ }
+ }
+ None
+ }
+ _ => None,
+ },
(&ty::TyRef(_, mutability), _) => {
// Check if it can work when put into a ref. For example:
//
}
None
}
+ (_, &ty::TyRef(_, checked)) => {
+ // We have `&T`, check if what was expected was `T`. If so,
+ // we may want to suggest adding a `*`, or removing
+ // a `&`.
+ //
+ // (But, also check check the `expn_info()` to see if this is
+ // a macro; if so, it's hard to extract the text and make a good
+ // suggestion, so don't bother.)
+ if self.infcx.can_sub(self.param_env, checked.ty, &expected).is_ok() &&
+ expr.span.ctxt().outer().expn_info().is_none() {
+ match expr.node {
+ // Maybe remove `&`?
+ hir::ExprAddrOf(_, ref expr) => {
+ if let Ok(code) = self.tcx.sess.codemap().span_to_snippet(expr.span) {
+ return Some(format!("try with `{}`", code));
+ }
+ }
+
+ // Maybe add `*`? Only if `T: Copy`.
+ _ => {
+ if !self.infcx.type_moves_by_default(self.param_env,
+ checked.ty,
+ expr.span) {
+ let sp = self.sess().codemap().call_span_if_macro(expr.span);
+ if let Ok(code) = self.tcx.sess.codemap().span_to_snippet(sp) {
+ return Some(format!("try with `*{}`", code));
+ }
+ }
+ },
+ }
+ }
+ None
+ }
_ => None,
}
}