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rustc: Don't error out early when constructing a boxed trait.

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This improves error messages a bit and helps pave the way for "@int as @Trait"
(as opposed to "int as @Trait").
This commit is contained in:
Patrick Walton 2012-10-02 15:29:16 -07:00
parent f78cdcb636
commit 5e7ff924b5
1 changed files with 35 additions and 20 deletions
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55
src/rustc/middle/typeck/check/vtable.rs
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@ -51,8 +51,13 @@ fn lookup_vtables(fcx: @fn_ctxt,
match *bound {
ty::bound_trait(i_ty) => {
let i_ty = ty::subst(tcx, substs, i_ty);
result.push(lookup_vtable(fcx, expr, *ty, i_ty,
allow_unsafe, is_early));
match lookup_vtable(fcx, expr, *ty, i_ty, allow_unsafe,
is_early) {
None => {}
Some(vtable) => {
result.push(vtable);
}
}
}
_ => ()
}
@ -91,7 +96,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
trait_ty: ty::t,
allow_unsafe: bool,
is_early: bool)
-> vtable_origin
-> Option<vtable_origin>
{
debug!("lookup_vtable(ty=%s, trait_ty=%s)",
@ -113,7 +118,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
// The type has unconstrained type variables in it, so we can't
// do early resolution on it. Return some completely bogus vtable
// information: we aren't storing it anyways.
return vtable_param(0, 0);
return Some(vtable_param(0, 0));
}
};
@ -135,7 +140,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
idid);
relate_trait_tys(fcx, expr,
trait_ty, ity);
return vtable_param(n, n_bound);
return Some(vtable_param(n, n_bound));
}
}
_ => tcx.sess.impossible_case(
@ -170,7 +175,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
}
}
}
return vtable_trait(did, substs.tps);
return Some(vtable_trait(did, substs.tps));
}
_ => {
@ -303,7 +308,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
None => {
assert is_early;
// Bail out with a bogus answer
return vtable_param(0, 0);
return Some(vtable_param(0, 0));
}
};
@ -341,23 +346,20 @@ fn lookup_vtable(fcx: @fn_ctxt,
match found.len() {
0 => { /* fallthrough */ }
1 => { return found[0]; }
1 => { return Some(found[0]); }
_ => {
if !is_early {
fcx.ccx.tcx.sess.span_err(
expr.span,
~"multiple applicable methods in scope");
}
return found[0];
return Some(found[0]);
}
}
}
}
tcx.sess.span_fatal(
expr.span,
fmt!("failed to find an implementation of trait %s for %s",
ty_to_str(tcx, trait_ty), ty_to_str(tcx, ty)));
return None;
}
fn fixup_ty(fcx: @fn_ctxt,
@ -459,13 +461,26 @@ fn early_resolve_expr(ex: @ast::expr, &&fcx: @fn_ctxt, is_early: bool) {
Look up vtables for the type we're casting to,
passing in the source and target type
*/
let vtable = lookup_vtable(fcx, ex, fcx.expr_ty(src),
target_ty, true, is_early);
/*
Map this expression to that vtable (that is: "ex has
vtable <vtable>")
*/
if !is_early { cx.vtable_map.insert(ex.id, @~[vtable]); }
let ty = fcx.expr_ty(src);
let vtable_opt = lookup_vtable(fcx, ex, ty, target_ty, true,
is_early);
match vtable_opt {
None => {
fcx.tcx().sess.span_err(
ex.span,
fmt!("failed to find an implementation of trait %s \
for %s",
ty_to_str(fcx.tcx(), target_ty),
ty_to_str(fcx.tcx(), ty)));
}
Some(vtable) => {
/*
Map this expression to that vtable (that is: "ex has
vtable <vtable>")
*/
if !is_early { cx.vtable_map.insert(ex.id, @~[vtable]); }
}
}
}
_ => ()
}