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Implement numeric fallback #20189

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Jan 2, 2015
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21 changes: 20 additions & 1 deletion src/librustc/middle/infer/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ pub use self::freshen::TypeFreshener;

use middle::subst;
use middle::subst::Substs;
use middle::ty::{TyVid, IntVid, FloatVid, RegionVid};
use middle::ty::{TyVid, IntVid, FloatVid, RegionVid, UnconstrainedNumeric};
use middle::ty::replace_late_bound_regions;
use middle::ty::{mod, Ty};
use middle::ty_fold::{TypeFolder, TypeFoldable};
Expand Down Expand Up @@ -525,6 +525,25 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
freshen::TypeFreshener::new(self)
}

pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
use middle::ty::UnconstrainedNumeric::{Neither, UnconstrainedInt, UnconstrainedFloat};
match ty.sty {
ty::ty_infer(ty::IntVar(vid)) => {
match self.int_unification_table.borrow_mut().get(self.tcx, vid).value {
None => UnconstrainedInt,
_ => Neither,
}
},
ty::ty_infer(ty::FloatVar(vid)) => {
match self.float_unification_table.borrow_mut().get(self.tcx, vid).value {
None => return UnconstrainedFloat,
_ => Neither,
}
},
_ => Neither,
}
}

pub fn combine_fields<'b>(&'b self, a_is_expected: bool, trace: TypeTrace<'tcx>)
-> CombineFields<'b, 'tcx> {
CombineFields {infcx: self,
Expand Down
8 changes: 8 additions & 0 deletions src/librustc/middle/ty.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1641,6 +1641,14 @@ pub enum InferTy {
FreshIntTy(u32),
}

#[deriving(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Show, Copy)]
pub enum UnconstrainedNumeric {
UnconstrainedFloat,
UnconstrainedInt,
Neither,
}


#[deriving(Clone, RustcEncodable, RustcDecodable, Eq, Hash, Show, Copy)]
pub enum InferRegion {
ReVar(RegionVid),
Expand Down
19 changes: 16 additions & 3 deletions src/librustc_typeck/check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -453,7 +453,6 @@ fn check_bare_fn<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,

vtable::select_all_fcx_obligations_or_error(&fcx);
regionck::regionck_fn(&fcx, id, decl, body);
fcx.default_diverging_type_variables_to_nil();
writeback::resolve_type_vars_in_fn(&fcx, decl, body);
}
_ => ccx.tcx.sess.impossible_case(body.span,
Expand Down Expand Up @@ -1666,10 +1665,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}

pub fn default_diverging_type_variables_to_nil(&self) {
/// Apply "fallbacks" to some types
/// ! gets replaced with (), unconstrained ints with i32, and unconstrained floats with f64.
pub fn default_type_parameters(&self) {
use middle::ty::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat, Neither};
for (_, &ref ty) in self.inh.node_types.borrow_mut().iter_mut() {
if self.infcx().type_var_diverges(self.infcx().resolve_type_vars_if_possible(ty)) {
let resolved = self.infcx().resolve_type_vars_if_possible(ty);
if self.infcx().type_var_diverges(resolved) {
demand::eqtype(self, codemap::DUMMY_SP, *ty, ty::mk_nil(self.tcx()));
} else {
match self.infcx().type_is_unconstrained_numeric(resolved) {
UnconstrainedInt => {
demand::eqtype(self, codemap::DUMMY_SP, *ty, self.tcx().types.i32)
},
UnconstrainedFloat => {
demand::eqtype(self, codemap::DUMMY_SP, *ty, self.tcx().types.f64)
}
Neither => { }
}
}
}
}
Expand Down
3 changes: 3 additions & 0 deletions src/librustc_typeck/check/vtable.rs
Original file line number Diff line number Diff line change
Expand Up @@ -407,6 +407,9 @@ pub fn register_object_cast_obligations<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
pub fn select_all_fcx_obligations_or_error(fcx: &FnCtxt) {
debug!("select_all_fcx_obligations_or_error");

select_fcx_obligations_where_possible(fcx);
fcx.default_type_parameters();

let mut fulfillment_cx = fcx.inh.fulfillment_cx.borrow_mut();
let r = fulfillment_cx.select_all_or_error(fcx.infcx(),
&fcx.inh.param_env,
Expand Down
3 changes: 2 additions & 1 deletion src/test/compile-fail/issue-16966.rs
Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,9 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// error-pattern:type annotations required
fn main() {
panic!(
1.2 //~ ERROR cannot determine a type for this expression
std::default::Default::default()
);
}
Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ where T : Convert<U>
}

fn a() {
test(22_i32, 44); //~ ERROR type annotations required
test(22_i32, std::default::Default::default()); //~ ERROR type annotations required
}

fn main() {}
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// error-pattern:explicit panic

fn foo<T>(t: T) {}
fn main() { foo(panic!()) }
//~^ ERROR type annotations required
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@
fn foo(_: *const ()) {}

fn main() {
let a = 3; //~ ERROR cannot determine a type for this local variable
let a = 3;
foo(&a as *const _ as *const ());
}

Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,5 @@

fn main() {
println!("{}", std::mem::size_of_val(&1));
//~^ ERROR cannot determine a type for this expression
}

Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,5 @@
// except according to those terms.

fn main() {
panic!(
1.2
//~^ ERROR cannot determine the type of this number; add a suffix to specify the type explicitly
);
println!("{}", 1.2);
}
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,5 @@

fn main() {
let mut array = [1, 2, 3];
//~^ ERROR cannot determine a type for this local variable: cannot determine the type of this integ
let pie_slice = array[1..2];
}
Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,5 @@

pub fn main() {
let x = [1, 2, 3];
//~^ ERROR cannot determine a type for this local variable: cannot determine the type of this
let y = x.as_slice();
}

This file was deleted.

Original file line number Diff line number Diff line change
Expand Up @@ -36,11 +36,10 @@ where T : Convert<U>
}

fn main() {
use std::default::Default;
// T = i16, U = u32
test(22_i16, 44, 2, 4);
test(22, 44_u32, 2, 4);
test(22_i16, Default::default(), 2, 4);

// T = u32, U = i16
test(22_u32, 44, 4, 2);
test(22, 44_i16, 4, 2);
test(22_u32, Default::default(), 4, 2);
}