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//! Type inference for patterns.
use std::iter::repeat;
use std::sync::Arc;
use test_utils::tested_by;
use super::{BindingMode, InferenceContext};
use crate::{
db::HirDatabase,
expr::{BindingAnnotation, Pat, PatId, RecordFieldPat},
ty::{Mutability, Substs, Ty, TypeCtor, TypeWalk},
Name, Path,
};
impl<'a, D: HirDatabase> InferenceContext<'a, D> {
fn infer_tuple_struct_pat(
&mut self,
path: Option<&Path>,
subpats: &[PatId],
expected: &Ty,
default_bm: BindingMode,
) -> Ty {
let (ty, def) = self.resolve_variant(path);
self.unify(&ty, expected);
let substs = ty.substs().unwrap_or_else(Substs::empty);
let field_tys = def.map(|it| self.db.field_types(it.into())).unwrap_or_default();
for (i, &subpat) in subpats.iter().enumerate() {
let expected_ty = def
.and_then(|d| d.field(self.db, &Name::new_tuple_field(i)))
.map_or(Ty::Unknown, |field| field_tys[field.id].clone())
.subst(&substs);
let expected_ty = self.normalize_associated_types_in(expected_ty);
self.infer_pat(subpat, &expected_ty, default_bm);
}
ty
}
fn infer_record_pat(
&mut self,
path: Option<&Path>,
subpats: &[RecordFieldPat],
expected: &Ty,
default_bm: BindingMode,
id: PatId,
) -> Ty {
let (ty, def) = self.resolve_variant(path);
if let Some(variant) = def {
self.write_variant_resolution(id.into(), variant);
}
self.unify(&ty, expected);
let substs = ty.substs().unwrap_or_else(Substs::empty);
let field_tys = def.map(|it| self.db.field_types(it.into())).unwrap_or_default();
for subpat in subpats {
let matching_field = def.and_then(|it| it.field(self.db, &subpat.name));
let expected_ty = matching_field
.map_or(Ty::Unknown, |field| field_tys[field.id].clone())
.subst(&substs);
let expected_ty = self.normalize_associated_types_in(expected_ty);
self.infer_pat(subpat.pat, &expected_ty, default_bm);
}
ty
}
pub(super) fn infer_pat(
&mut self,
pat: PatId,
mut expected: &Ty,
mut default_bm: BindingMode,
) -> Ty {
let body = Arc::clone(&self.body); // avoid borrow checker problem
let is_non_ref_pat = match &body[pat] {
Pat::Tuple(..)
| Pat::TupleStruct { .. }
| Pat::Record { .. }
| Pat::Range { .. }
| Pat::Slice { .. } => true,
// FIXME: Path/Lit might actually evaluate to ref, but inference is unimplemented.
Pat::Path(..) | Pat::Lit(..) => true,
Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Missing => false,
};
if is_non_ref_pat {
while let Some((inner, mutability)) = expected.as_reference() {
expected = inner;
default_bm = match default_bm {
BindingMode::Move => BindingMode::Ref(mutability),
BindingMode::Ref(Mutability::Shared) => BindingMode::Ref(Mutability::Shared),
BindingMode::Ref(Mutability::Mut) => BindingMode::Ref(mutability),
}
}
} else if let Pat::Ref { .. } = &body[pat] {
tested_by!(match_ergonomics_ref);
// When you encounter a `&pat` pattern, reset to Move.
// This is so that `w` is by value: `let (_, &w) = &(1, &2);`
default_bm = BindingMode::Move;
}
// Lose mutability.
let default_bm = default_bm;
let expected = expected;
let ty = match &body[pat] {
Pat::Tuple(ref args) => {
let expectations = match expected.as_tuple() {
Some(parameters) => &*parameters.0,
_ => &[],
};
let expectations_iter = expectations.iter().chain(repeat(&Ty::Unknown));
let inner_tys = args
.iter()
.zip(expectations_iter)
.map(|(&pat, ty)| self.infer_pat(pat, ty, default_bm))
.collect();
Ty::apply(TypeCtor::Tuple { cardinality: args.len() as u16 }, Substs(inner_tys))
}
Pat::Ref { pat, mutability } => {
let expectation = match expected.as_reference() {
Some((inner_ty, exp_mut)) => {
if *mutability != exp_mut {
// FIXME: emit type error?
}
inner_ty
}
_ => &Ty::Unknown,
};
let subty = self.infer_pat(*pat, expectation, default_bm);
Ty::apply_one(TypeCtor::Ref(*mutability), subty)
}
Pat::TupleStruct { path: p, args: subpats } => {
self.infer_tuple_struct_pat(p.as_ref(), subpats, expected, default_bm)
}
Pat::Record { path: p, args: fields } => {
self.infer_record_pat(p.as_ref(), fields, expected, default_bm, pat)
}
Pat::Path(path) => {
// FIXME use correct resolver for the surrounding expression
let resolver = self.resolver.clone();
self.infer_path(&resolver, &path, pat.into()).unwrap_or(Ty::Unknown)
}
Pat::Bind { mode, name: _, subpat } => {
let mode = if mode == &BindingAnnotation::Unannotated {
default_bm
} else {
BindingMode::convert(*mode)
};
let inner_ty = if let Some(subpat) = subpat {
self.infer_pat(*subpat, expected, default_bm)
} else {
expected.clone()
};
let inner_ty = self.insert_type_vars_shallow(inner_ty);
let bound_ty = match mode {
BindingMode::Ref(mutability) => {
Ty::apply_one(TypeCtor::Ref(mutability), inner_ty.clone())
}
BindingMode::Move => inner_ty.clone(),
};
let bound_ty = self.resolve_ty_as_possible(&mut vec![], bound_ty);
self.write_pat_ty(pat, bound_ty);
return inner_ty;
}
_ => Ty::Unknown,
};
// use a new type variable if we got Ty::Unknown here
let ty = self.insert_type_vars_shallow(ty);
self.unify(&ty, expected);
let ty = self.resolve_ty_as_possible(&mut vec![], ty);
self.write_pat_ty(pat, ty.clone());
ty
}
}
|
