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Implement BindingMode for pattern matching.

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Implement `BindingMode` for pattern matching, so that types can be
correctly inferred using match ergonomics. The binding mode defaults to
`Move` (referred to as 'BindingMode::BindByValue` in rustc), and is
updated by automatic dereferencing of the value being matched.
This commit is contained in:
Michael Killough 2019-03-16 18:13:13 +00:00
parent 97a87bf3a6
commit b42c5ced68
2 changed files with 154 additions and 62 deletions
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95
crates/ra_hir/src/ty/infer.rs
View File

@ -63,6 +63,24 @@ enum ExprOrPatId {
impl_froms!(ExprOrPatId: ExprId, PatId);
/// Binding modes inferred for patterns.
/// https://doc.rust-lang.org/reference/patterns.html#binding-modes
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
enum BindingMode {
Move,
Ref(Mutability),
}
impl BindingMode {
pub fn convert(annotation: &BindingAnnotation) -> BindingMode {
match annotation {
BindingAnnotation::Unannotated | BindingAnnotation::Mutable => BindingMode::Move,
BindingAnnotation::Ref => BindingMode::Ref(Mutability::Shared),
BindingAnnotation::RefMut => BindingMode::Ref(Mutability::Mut),
}
}
}
/// The result of type inference: A mapping from expressions and patterns to types.
#[derive(Clone, PartialEq, Eq, Debug)]
pub struct InferenceResult {
@ -530,6 +548,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
path: Option<&Path>,
subpats: &[PatId],
expected: &Ty,
default_bm: BindingMode,
) -> Ty {
let (ty, def) = self.resolve_variant(path);
@ -542,13 +561,19 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
.and_then(|d| d.field(self.db, &Name::tuple_field_name(i)))
.map_or(Ty::Unknown, |field| field.ty(self.db))
.subst(&substs);
self.infer_pat(subpat, &expected_ty);
self.infer_pat(subpat, &expected_ty, default_bm);
}
ty
}
fn infer_struct_pat(&mut self, path: Option<&Path>, subpats: &[FieldPat], expected: &Ty) -> Ty {
fn infer_struct_pat(
&mut self,
path: Option<&Path>,
subpats: &[FieldPat],
expected: &Ty,
default_bm: BindingMode,
) -> Ty {
let (ty, def) = self.resolve_variant(path);
self.unify(&ty, expected);
@ -559,15 +584,42 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
let matching_field = def.and_then(|it| it.field(self.db, &subpat.name));
let expected_ty =
matching_field.map_or(Ty::Unknown, |field| field.ty(self.db)).subst(&substs);
self.infer_pat(subpat.pat, &expected_ty);
self.infer_pat(subpat.pat, &expected_ty, default_bm);
}
ty
}
fn infer_pat(&mut self, pat: PatId, expected: &Ty) -> Ty {
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::Struct { .. }
| Pat::Range { .. }
| Pat::Slice { .. } => true,
// TODO: 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 Ty::Ref(inner, mutability) = expected {
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] {
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 {
@ -579,7 +631,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
let inner_tys = args
.iter()
.zip(expectations_iter)
.map(|(&pat, ty)| self.infer_pat(pat, ty))
.map(|(&pat, ty)| self.infer_pat(pat, ty, default_bm))
.collect::<Vec<_>>()
.into();
@ -595,14 +647,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
_ => &Ty::Unknown,
};
let subty = self.infer_pat(*pat, expectation);
let subty = self.infer_pat(*pat, expectation, default_bm);
Ty::Ref(subty.into(), *mutability)
}
Pat::TupleStruct { path: ref p, args: ref subpats } => {
self.infer_tuple_struct_pat(p.as_ref(), subpats, expected)
self.infer_tuple_struct_pat(p.as_ref(), subpats, expected, default_bm)
}
Pat::Struct { path: ref p, args: ref fields } => {
self.infer_struct_pat(p.as_ref(), fields, expected)
self.infer_struct_pat(p.as_ref(), fields, expected, default_bm)
}
Pat::Path(path) => {
// TODO use correct resolver for the surrounding expression
@ -610,17 +662,26 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
self.infer_path_expr(&resolver, &path, pat.into()).unwrap_or(Ty::Unknown)
}
Pat::Bind { mode, name: _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)
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 {
BindingAnnotation::Ref => Ty::Ref(inner_ty.clone().into(), Mutability::Shared),
BindingAnnotation::RefMut => Ty::Ref(inner_ty.clone().into(), Mutability::Mut),
BindingAnnotation::Mutable | BindingAnnotation::Unannotated => inner_ty.clone(),
BindingMode::Ref(Mutability::Shared) => {
Ty::Ref(inner_ty.clone().into(), Mutability::Shared)
}
BindingMode::Ref(Mutability::Mut) => {
Ty::Ref(inner_ty.clone().into(), Mutability::Mut)
}
BindingMode::Move => inner_ty.clone(),
};
let bound_ty = self.resolve_ty_as_possible(&mut vec![], bound_ty);
self.write_pat_ty(pat, bound_ty);
@ -700,7 +761,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
}
Expr::For { iterable, body, pat } => {
let _iterable_ty = self.infer_expr(*iterable, &Expectation::none());
self.infer_pat(*pat, &Ty::Unknown);
self.infer_pat(*pat, &Ty::Unknown, BindingMode::Move);
self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
Ty::unit()
}
@ -714,7 +775,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
} else {
Ty::Unknown
};
self.infer_pat(*arg_pat, &expected);
self.infer_pat(*arg_pat, &expected, BindingMode::Move);
}
// TODO: infer lambda type etc.
@ -804,7 +865,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
for arm in arms {
for &pat in &arm.pats {
let _pat_ty = self.infer_pat(pat, &input_ty);
let _pat_ty = self.infer_pat(pat, &input_ty, BindingMode::Move);
}
if let Some(guard_expr) = arm.guard {
self.infer_expr(guard_expr, &Expectation::has_type(Ty::Bool));
@ -1004,7 +1065,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
decl_ty
};
self.infer_pat(*pat, &ty);
self.infer_pat(*pat, &ty, BindingMode::Move);
}
Statement::Expr(expr) => {
self.infer_expr(*expr, &Expectation::none());
@ -1020,7 +1081,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
for (type_ref, pat) in signature.params().iter().zip(body.params()) {
let ty = self.make_ty(type_ref);
self.infer_pat(*pat, &ty);
self.infer_pat(*pat, &ty, BindingMode::Move);
}
self.return_ty = self.make_ty(signature.ret_type());
}

121
crates/ra_hir/src/ty/tests.rs
View File

@ -756,6 +756,8 @@ fn test(x: &str, y: isize) {
fn infer_pattern() {
assert_snapshot_matches!(
infer(r#"
struct A<T>(T);
fn test(x: &i32) {
let y = x;
let &z = x;
@ -772,6 +774,12 @@ fn test(x: &i32) {
let lambda = |a: u64, b, c: i32| { a + b; c };
let A(n) = &A(1);
let A(n) = &mut A(1);
let v = &(1, &2);
let (_, &w) = v;
let ref ref_to_x = x;
let mut mut_x = x;
let ref mut mut_ref_to_x = x;
@ -779,53 +787,76 @@ fn test(x: &i32) {
}
"#),
@r###"
[9; 10) 'x': &i32
[18; 369) '{ ...o_x; }': ()
[28; 29) 'y': &i32
[32; 33) 'x': &i32
[43; 45) '&z': &i32
[44; 45) 'z': i32
[48; 49) 'x': &i32
[59; 60) 'a': i32
[63; 64) 'z': i32
[74; 80) '(c, d)': (i32, &str)
[75; 76) 'c': i32
[78; 79) 'd': &str
[83; 95) '(1, "hello")': (i32, &str)
[84; 85) '1': i32
[87; 94) '"hello"': &str
[102; 152) 'for (e... }': ()
[106; 112) '(e, f)': ({unknown}, {unknown})
[107; 108) 'e': {unknown}
[110; 111) 'f': {unknown}
[116; 125) 'some_iter': {unknown}
[126; 152) '{ ... }': ()
[140; 141) 'g': {unknown}
[144; 145) 'e': {unknown}
[158; 205) 'if let... }': ()
[165; 170) '[val]': {unknown}
[173; 176) 'opt': {unknown}
[177; 205) '{ ... }': ()
[191; 192) 'h': {unknown}
[195; 198) 'val': {unknown}
[215; 221) 'lambda': {unknown}
[224; 256) '|a: u6...b; c }': {unknown}
[225; 226) 'a': u64
[233; 234) 'b': u64
[236; 237) 'c': i32
[244; 256) '{ a + b; c }': i32
[246; 247) 'a': u64
[246; 251) 'a + b': u64
[26; 27) 'x': &i32
[35; 479) '{ ...o_x; }': ()
[45; 46) 'y': &i32
[49; 50) 'x': &i32
[60; 62) '&z': &i32
[61; 62) 'z': i32
[65; 66) 'x': &i32
[76; 77) 'a': i32
[80; 81) 'z': i32
[91; 97) '(c, d)': (i32, &str)
[92; 93) 'c': i32
[95; 96) 'd': &str
[100; 112) '(1, "hello")': (i32, &str)
[101; 102) '1': i32
[104; 111) '"hello"': &str
[119; 169) 'for (e... }': ()
[123; 129) '(e, f)': ({unknown}, {unknown})
[124; 125) 'e': {unknown}
[127; 128) 'f': {unknown}
[133; 142) 'some_iter': {unknown}
[143; 169) '{ ... }': ()
[157; 158) 'g': {unknown}
[161; 162) 'e': {unknown}
[175; 222) 'if let... }': ()
[182; 187) '[val]': {unknown}
[190; 193) 'opt': {unknown}
[194; 222) '{ ... }': ()
[208; 209) 'h': {unknown}
[212; 215) 'val': {unknown}
[232; 238) 'lambda': {unknown}
[241; 273) '|a: u6...b; c }': {unknown}
[242; 243) 'a': u64
[250; 251) 'b': u64
[253; 254) 'c': i32
[267; 279) 'ref ref_to_x': &&i32
[282; 283) 'x': &i32
[293; 302) 'mut mut_x': &i32
[305; 306) 'x': &i32
[316; 336) 'ref mu...f_to_x': &mut &i32
[339; 340) 'x': &i32
[350; 351) 'k': &mut &i32
[354; 366) 'mut_ref_to_x': &mut &i32"###
[261; 273) '{ a + b; c }': i32
[263; 264) 'a': u64
[263; 268) 'a + b': u64
[267; 268) 'b': u64
[270; 271) 'c': i32
[284; 288) 'A(n)': A<i32>
[286; 287) 'n': &i32
[291; 296) '&A(1)': &A<i32>
[292; 293) 'A': A<i32>(T) -> A<T>
[292; 296) 'A(1)': A<i32>
[294; 295) '1': i32
[306; 310) 'A(n)': A<i32>
[308; 309) 'n': &mut i32
[313; 322) '&mut A(1)': &mut A<i32>
[318; 319) 'A': A<i32>(T) -> A<T>
[318; 322) 'A(1)': A<i32>
[320; 321) '1': i32
[333; 334) 'v': &(i32, &i32)
[337; 345) '&(1, &2)': &(i32, &i32)
[338; 345) '(1, &2)': (i32, &i32)
[339; 340) '1': i32
[342; 344) '&2': &i32
[343; 344) '2': i32
[355; 362) '(_, &w)': (i32, &i32)
[356; 357) '_': i32
[359; 361) '&w': &i32
[360; 361) 'w': i32
[365; 366) 'v': &(i32, &i32)
[377; 389) 'ref ref_to_x': &&i32
[392; 393) 'x': &i32
[403; 412) 'mut mut_x': &i32
[415; 416) 'x': &i32
[426; 446) 'ref mu...f_to_x': &mut &i32
[449; 450) 'x': &i32
[460; 461) 'k': &mut &i32
[464; 476) 'mut_ref_to_x': &mut &i32"###
);
}