diff options
author | Aleksey Kladov <[email protected]> | 2020-08-13 15:35:29 +0100 |
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committer | Aleksey Kladov <[email protected]> | 2020-08-13 15:35:29 +0100 |
commit | 6a77ec7bbe6ddbf663dce9529d11d1bb56c5489a (patch) | |
tree | b6e3d7e0109eb82bca75b5ebc35a7d723542b8dd /crates/ra_hir_ty/src/diagnostics/match_check.rs | |
parent | 50f8c1ebf23f634b68529603a917e3feeda457fa (diff) |
Rename ra_hir_ty -> hir_ty
Diffstat (limited to 'crates/ra_hir_ty/src/diagnostics/match_check.rs')
-rw-r--r-- | crates/ra_hir_ty/src/diagnostics/match_check.rs | 1421 |
1 files changed, 0 insertions, 1421 deletions
diff --git a/crates/ra_hir_ty/src/diagnostics/match_check.rs b/crates/ra_hir_ty/src/diagnostics/match_check.rs deleted file mode 100644 index 7f007f1d6..000000000 --- a/crates/ra_hir_ty/src/diagnostics/match_check.rs +++ /dev/null | |||
@@ -1,1421 +0,0 @@ | |||
1 | //! This module implements match statement exhaustiveness checking and usefulness checking | ||
2 | //! for match arms. | ||
3 | //! | ||
4 | //! It is modeled on the rustc module `librustc_mir_build::hair::pattern::_match`, which | ||
5 | //! contains very detailed documentation about the algorithms used here. I've duplicated | ||
6 | //! most of that documentation below. | ||
7 | //! | ||
8 | //! This file includes the logic for exhaustiveness and usefulness checking for | ||
9 | //! pattern-matching. Specifically, given a list of patterns for a type, we can | ||
10 | //! tell whether: | ||
11 | //! - (a) the patterns cover every possible constructor for the type (exhaustiveness). | ||
12 | //! - (b) each pattern is necessary (usefulness). | ||
13 | //! | ||
14 | //! The algorithm implemented here is a modified version of the one described in | ||
15 | //! <http://moscova.inria.fr/~maranget/papers/warn/index.html>. | ||
16 | //! However, to save future implementors from reading the original paper, we | ||
17 | //! summarise the algorithm here to hopefully save time and be a little clearer | ||
18 | //! (without being so rigorous). | ||
19 | //! | ||
20 | //! The core of the algorithm revolves about a "usefulness" check. In particular, we | ||
21 | //! are trying to compute a predicate `U(P, p)` where `P` is a list of patterns (we refer to this as | ||
22 | //! a matrix). `U(P, p)` represents whether, given an existing list of patterns | ||
23 | //! `P_1 ..= P_m`, adding a new pattern `p` will be "useful" (that is, cover previously- | ||
24 | //! uncovered values of the type). | ||
25 | //! | ||
26 | //! If we have this predicate, then we can easily compute both exhaustiveness of an | ||
27 | //! entire set of patterns and the individual usefulness of each one. | ||
28 | //! (a) the set of patterns is exhaustive iff `U(P, _)` is false (i.e., adding a wildcard | ||
29 | //! match doesn't increase the number of values we're matching) | ||
30 | //! (b) a pattern `P_i` is not useful if `U(P[0..=(i-1), P_i)` is false (i.e., adding a | ||
31 | //! pattern to those that have come before it doesn't increase the number of values | ||
32 | //! we're matching). | ||
33 | //! | ||
34 | //! During the course of the algorithm, the rows of the matrix won't just be individual patterns, | ||
35 | //! but rather partially-deconstructed patterns in the form of a list of patterns. The paper | ||
36 | //! calls those pattern-vectors, and we will call them pattern-stacks. The same holds for the | ||
37 | //! new pattern `p`. | ||
38 | //! | ||
39 | //! For example, say we have the following: | ||
40 | //! | ||
41 | //! ```ignore | ||
42 | //! // x: (Option<bool>, Result<()>) | ||
43 | //! match x { | ||
44 | //! (Some(true), _) => (), | ||
45 | //! (None, Err(())) => (), | ||
46 | //! (None, Err(_)) => (), | ||
47 | //! } | ||
48 | //! ``` | ||
49 | //! | ||
50 | //! Here, the matrix `P` starts as: | ||
51 | //! | ||
52 | //! ```text | ||
53 | //! [ | ||
54 | //! [(Some(true), _)], | ||
55 | //! [(None, Err(()))], | ||
56 | //! [(None, Err(_))], | ||
57 | //! ] | ||
58 | //! ``` | ||
59 | //! | ||
60 | //! We can tell it's not exhaustive, because `U(P, _)` is true (we're not covering | ||
61 | //! `[(Some(false), _)]`, for instance). In addition, row 3 is not useful, because | ||
62 | //! all the values it covers are already covered by row 2. | ||
63 | //! | ||
64 | //! A list of patterns can be thought of as a stack, because we are mainly interested in the top of | ||
65 | //! the stack at any given point, and we can pop or apply constructors to get new pattern-stacks. | ||
66 | //! To match the paper, the top of the stack is at the beginning / on the left. | ||
67 | //! | ||
68 | //! There are two important operations on pattern-stacks necessary to understand the algorithm: | ||
69 | //! | ||
70 | //! 1. We can pop a given constructor off the top of a stack. This operation is called | ||
71 | //! `specialize`, and is denoted `S(c, p)` where `c` is a constructor (like `Some` or | ||
72 | //! `None`) and `p` a pattern-stack. | ||
73 | //! If the pattern on top of the stack can cover `c`, this removes the constructor and | ||
74 | //! pushes its arguments onto the stack. It also expands OR-patterns into distinct patterns. | ||
75 | //! Otherwise the pattern-stack is discarded. | ||
76 | //! This essentially filters those pattern-stacks whose top covers the constructor `c` and | ||
77 | //! discards the others. | ||
78 | //! | ||
79 | //! For example, the first pattern above initially gives a stack `[(Some(true), _)]`. If we | ||
80 | //! pop the tuple constructor, we are left with `[Some(true), _]`, and if we then pop the | ||
81 | //! `Some` constructor we get `[true, _]`. If we had popped `None` instead, we would get | ||
82 | //! nothing back. | ||
83 | //! | ||
84 | //! This returns zero or more new pattern-stacks, as follows. We look at the pattern `p_1` | ||
85 | //! on top of the stack, and we have four cases: | ||
86 | //! | ||
87 | //! * 1.1. `p_1 = c(r_1, .., r_a)`, i.e. the top of the stack has constructor `c`. We push onto | ||
88 | //! the stack the arguments of this constructor, and return the result: | ||
89 | //! | ||
90 | //! r_1, .., r_a, p_2, .., p_n | ||
91 | //! | ||
92 | //! * 1.2. `p_1 = c'(r_1, .., r_a')` where `c ≠ c'`. We discard the current stack and return | ||
93 | //! nothing. | ||
94 | //! * 1.3. `p_1 = _`. We push onto the stack as many wildcards as the constructor `c` has | ||
95 | //! arguments (its arity), and return the resulting stack: | ||
96 | //! | ||
97 | //! _, .., _, p_2, .., p_n | ||
98 | //! | ||
99 | //! * 1.4. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting stack: | ||
100 | //! | ||
101 | //! S(c, (r_1, p_2, .., p_n)) | ||
102 | //! S(c, (r_2, p_2, .., p_n)) | ||
103 | //! | ||
104 | //! 2. We can pop a wildcard off the top of the stack. This is called `D(p)`, where `p` is | ||
105 | //! a pattern-stack. | ||
106 | //! This is used when we know there are missing constructor cases, but there might be | ||
107 | //! existing wildcard patterns, so to check the usefulness of the matrix, we have to check | ||
108 | //! all its *other* components. | ||
109 | //! | ||
110 | //! It is computed as follows. We look at the pattern `p_1` on top of the stack, | ||
111 | //! and we have three cases: | ||
112 | //! * 1.1. `p_1 = c(r_1, .., r_a)`. We discard the current stack and return nothing. | ||
113 | //! * 1.2. `p_1 = _`. We return the rest of the stack: | ||
114 | //! | ||
115 | //! p_2, .., p_n | ||
116 | //! | ||
117 | //! * 1.3. `p_1 = r_1 | r_2`. We expand the OR-pattern and then recurse on each resulting stack: | ||
118 | //! | ||
119 | //! D((r_1, p_2, .., p_n)) | ||
120 | //! D((r_2, p_2, .., p_n)) | ||
121 | //! | ||
122 | //! Note that the OR-patterns are not always used directly in Rust, but are used to derive the | ||
123 | //! exhaustive integer matching rules, so they're written here for posterity. | ||
124 | //! | ||
125 | //! Both those operations extend straightforwardly to a list or pattern-stacks, i.e. a matrix, by | ||
126 | //! working row-by-row. Popping a constructor ends up keeping only the matrix rows that start with | ||
127 | //! the given constructor, and popping a wildcard keeps those rows that start with a wildcard. | ||
128 | //! | ||
129 | //! | ||
130 | //! The algorithm for computing `U` | ||
131 | //! ------------------------------- | ||
132 | //! The algorithm is inductive (on the number of columns: i.e., components of tuple patterns). | ||
133 | //! That means we're going to check the components from left-to-right, so the algorithm | ||
134 | //! operates principally on the first component of the matrix and new pattern-stack `p`. | ||
135 | //! This algorithm is realised in the `is_useful` function. | ||
136 | //! | ||
137 | //! Base case (`n = 0`, i.e., an empty tuple pattern): | ||
138 | //! - If `P` already contains an empty pattern (i.e., if the number of patterns `m > 0`), then | ||
139 | //! `U(P, p)` is false. | ||
140 | //! - Otherwise, `P` must be empty, so `U(P, p)` is true. | ||
141 | //! | ||
142 | //! Inductive step (`n > 0`, i.e., whether there's at least one column [which may then be expanded | ||
143 | //! into further columns later]). We're going to match on the top of the new pattern-stack, `p_1`: | ||
144 | //! | ||
145 | //! - If `p_1 == c(r_1, .., r_a)`, i.e. we have a constructor pattern. | ||
146 | //! Then, the usefulness of `p_1` can be reduced to whether it is useful when | ||
147 | //! we ignore all the patterns in the first column of `P` that involve other constructors. | ||
148 | //! This is where `S(c, P)` comes in: | ||
149 | //! | ||
150 | //! ```text | ||
151 | //! U(P, p) := U(S(c, P), S(c, p)) | ||
152 | //! ``` | ||
153 | //! | ||
154 | //! This special case is handled in `is_useful_specialized`. | ||
155 | //! | ||
156 | //! For example, if `P` is: | ||
157 | //! | ||
158 | //! ```text | ||
159 | //! [ | ||
160 | //! [Some(true), _], | ||
161 | //! [None, 0], | ||
162 | //! ] | ||
163 | //! ``` | ||
164 | //! | ||
165 | //! and `p` is `[Some(false), 0]`, then we don't care about row 2 since we know `p` only | ||
166 | //! matches values that row 2 doesn't. For row 1 however, we need to dig into the | ||
167 | //! arguments of `Some` to know whether some new value is covered. So we compute | ||
168 | //! `U([[true, _]], [false, 0])`. | ||
169 | //! | ||
170 | //! - If `p_1 == _`, then we look at the list of constructors that appear in the first component of | ||
171 | //! the rows of `P`: | ||
172 | //! - If there are some constructors that aren't present, then we might think that the | ||
173 | //! wildcard `_` is useful, since it covers those constructors that weren't covered | ||
174 | //! before. | ||
175 | //! That's almost correct, but only works if there were no wildcards in those first | ||
176 | //! components. So we need to check that `p` is useful with respect to the rows that | ||
177 | //! start with a wildcard, if there are any. This is where `D` comes in: | ||
178 | //! `U(P, p) := U(D(P), D(p))` | ||
179 | //! | ||
180 | //! For example, if `P` is: | ||
181 | //! ```text | ||
182 | //! [ | ||
183 | //! [_, true, _], | ||
184 | //! [None, false, 1], | ||
185 | //! ] | ||
186 | //! ``` | ||
187 | //! and `p` is `[_, false, _]`, the `Some` constructor doesn't appear in `P`. So if we | ||
188 | //! only had row 2, we'd know that `p` is useful. However row 1 starts with a | ||
189 | //! wildcard, so we need to check whether `U([[true, _]], [false, 1])`. | ||
190 | //! | ||
191 | //! - Otherwise, all possible constructors (for the relevant type) are present. In this | ||
192 | //! case we must check whether the wildcard pattern covers any unmatched value. For | ||
193 | //! that, we can think of the `_` pattern as a big OR-pattern that covers all | ||
194 | //! possible constructors. For `Option`, that would mean `_ = None | Some(_)` for | ||
195 | //! example. The wildcard pattern is useful in this case if it is useful when | ||
196 | //! specialized to one of the possible constructors. So we compute: | ||
197 | //! `U(P, p) := ∃(k ϵ constructors) U(S(k, P), S(k, p))` | ||
198 | //! | ||
199 | //! For example, if `P` is: | ||
200 | //! ```text | ||
201 | //! [ | ||
202 | //! [Some(true), _], | ||
203 | //! [None, false], | ||
204 | //! ] | ||
205 | //! ``` | ||
206 | //! and `p` is `[_, false]`, both `None` and `Some` constructors appear in the first | ||
207 | //! components of `P`. We will therefore try popping both constructors in turn: we | ||
208 | //! compute `U([[true, _]], [_, false])` for the `Some` constructor, and `U([[false]], | ||
209 | //! [false])` for the `None` constructor. The first case returns true, so we know that | ||
210 | //! `p` is useful for `P`. Indeed, it matches `[Some(false), _]` that wasn't matched | ||
211 | //! before. | ||
212 | //! | ||
213 | //! - If `p_1 == r_1 | r_2`, then the usefulness depends on each `r_i` separately: | ||
214 | //! | ||
215 | //! ```text | ||
216 | //! U(P, p) := U(P, (r_1, p_2, .., p_n)) | ||
217 | //! || U(P, (r_2, p_2, .., p_n)) | ||
218 | //! ``` | ||
219 | use std::sync::Arc; | ||
220 | |||
221 | use arena::Idx; | ||
222 | use hir_def::{ | ||
223 | adt::VariantData, | ||
224 | body::Body, | ||
225 | expr::{Expr, Literal, Pat, PatId}, | ||
226 | AdtId, EnumVariantId, VariantId, | ||
227 | }; | ||
228 | use smallvec::{smallvec, SmallVec}; | ||
229 | |||
230 | use crate::{db::HirDatabase, ApplicationTy, InferenceResult, Ty, TypeCtor}; | ||
231 | |||
232 | #[derive(Debug, Clone, Copy)] | ||
233 | /// Either a pattern from the source code being analyzed, represented as | ||
234 | /// as `PatId`, or a `Wild` pattern which is created as an intermediate | ||
235 | /// step in the match checking algorithm and thus is not backed by a | ||
236 | /// real `PatId`. | ||
237 | /// | ||
238 | /// Note that it is totally valid for the `PatId` variant to contain | ||
239 | /// a `PatId` which resolves to a `Wild` pattern, if that wild pattern | ||
240 | /// exists in the source code being analyzed. | ||
241 | enum PatIdOrWild { | ||
242 | PatId(PatId), | ||
243 | Wild, | ||
244 | } | ||
245 | |||
246 | impl PatIdOrWild { | ||
247 | fn as_pat(self, cx: &MatchCheckCtx) -> Pat { | ||
248 | match self { | ||
249 | PatIdOrWild::PatId(id) => cx.body.pats[id].clone(), | ||
250 | PatIdOrWild::Wild => Pat::Wild, | ||
251 | } | ||
252 | } | ||
253 | |||
254 | fn as_id(self) -> Option<PatId> { | ||
255 | match self { | ||
256 | PatIdOrWild::PatId(id) => Some(id), | ||
257 | PatIdOrWild::Wild => None, | ||
258 | } | ||
259 | } | ||
260 | } | ||
261 | |||
262 | impl From<PatId> for PatIdOrWild { | ||
263 | fn from(pat_id: PatId) -> Self { | ||
264 | Self::PatId(pat_id) | ||
265 | } | ||
266 | } | ||
267 | |||
268 | impl From<&PatId> for PatIdOrWild { | ||
269 | fn from(pat_id: &PatId) -> Self { | ||
270 | Self::PatId(*pat_id) | ||
271 | } | ||
272 | } | ||
273 | |||
274 | #[derive(Debug, Clone, Copy, PartialEq)] | ||
275 | pub(super) enum MatchCheckErr { | ||
276 | NotImplemented, | ||
277 | MalformedMatchArm, | ||
278 | /// Used when type inference cannot resolve the type of | ||
279 | /// a pattern or expression. | ||
280 | Unknown, | ||
281 | } | ||
282 | |||
283 | /// The return type of `is_useful` is either an indication of usefulness | ||
284 | /// of the match arm, or an error in the case the match statement | ||
285 | /// is made up of types for which exhaustiveness checking is currently | ||
286 | /// not completely implemented. | ||
287 | /// | ||
288 | /// The `std::result::Result` type is used here rather than a custom enum | ||
289 | /// to allow the use of `?`. | ||
290 | pub(super) type MatchCheckResult<T> = Result<T, MatchCheckErr>; | ||
291 | |||
292 | #[derive(Debug)] | ||
293 | /// A row in a Matrix. | ||
294 | /// | ||
295 | /// This type is modeled from the struct of the same name in `rustc`. | ||
296 | pub(super) struct PatStack(PatStackInner); | ||
297 | type PatStackInner = SmallVec<[PatIdOrWild; 2]>; | ||
298 | |||
299 | impl PatStack { | ||
300 | pub(super) fn from_pattern(pat_id: PatId) -> PatStack { | ||
301 | Self(smallvec!(pat_id.into())) | ||
302 | } | ||
303 | |||
304 | pub(super) fn from_wild() -> PatStack { | ||
305 | Self(smallvec!(PatIdOrWild::Wild)) | ||
306 | } | ||
307 | |||
308 | fn from_slice(slice: &[PatIdOrWild]) -> PatStack { | ||
309 | Self(SmallVec::from_slice(slice)) | ||
310 | } | ||
311 | |||
312 | fn from_vec(v: PatStackInner) -> PatStack { | ||
313 | Self(v) | ||
314 | } | ||
315 | |||
316 | fn get_head(&self) -> Option<PatIdOrWild> { | ||
317 | self.0.first().copied() | ||
318 | } | ||
319 | |||
320 | fn tail(&self) -> &[PatIdOrWild] { | ||
321 | self.0.get(1..).unwrap_or(&[]) | ||
322 | } | ||
323 | |||
324 | fn to_tail(&self) -> PatStack { | ||
325 | Self::from_slice(self.tail()) | ||
326 | } | ||
327 | |||
328 | fn replace_head_with<I, T>(&self, pats: I) -> PatStack | ||
329 | where | ||
330 | I: Iterator<Item = T>, | ||
331 | T: Into<PatIdOrWild>, | ||
332 | { | ||
333 | let mut patterns: PatStackInner = smallvec![]; | ||
334 | for pat in pats { | ||
335 | patterns.push(pat.into()); | ||
336 | } | ||
337 | for pat in &self.0[1..] { | ||
338 | patterns.push(*pat); | ||
339 | } | ||
340 | PatStack::from_vec(patterns) | ||
341 | } | ||
342 | |||
343 | /// Computes `D(self)`. | ||
344 | /// | ||
345 | /// See the module docs and the associated documentation in rustc for details. | ||
346 | fn specialize_wildcard(&self, cx: &MatchCheckCtx) -> Option<PatStack> { | ||
347 | if matches!(self.get_head()?.as_pat(cx), Pat::Wild) { | ||
348 | Some(self.to_tail()) | ||
349 | } else { | ||
350 | None | ||
351 | } | ||
352 | } | ||
353 | |||
354 | /// Computes `S(constructor, self)`. | ||
355 | /// | ||
356 | /// See the module docs and the associated documentation in rustc for details. | ||
357 | fn specialize_constructor( | ||
358 | &self, | ||
359 | cx: &MatchCheckCtx, | ||
360 | constructor: &Constructor, | ||
361 | ) -> MatchCheckResult<Option<PatStack>> { | ||
362 | let head = match self.get_head() { | ||
363 | Some(head) => head, | ||
364 | None => return Ok(None), | ||
365 | }; | ||
366 | |||
367 | let head_pat = head.as_pat(cx); | ||
368 | let result = match (head_pat, constructor) { | ||
369 | (Pat::Tuple { args: ref pat_ids, ellipsis }, Constructor::Tuple { arity: _ }) => { | ||
370 | if ellipsis.is_some() { | ||
371 | // If there are ellipsis here, we should add the correct number of | ||
372 | // Pat::Wild patterns to `pat_ids`. We should be able to use the | ||
373 | // constructors arity for this, but at the time of writing we aren't | ||
374 | // correctly calculating this arity when ellipsis are present. | ||
375 | return Err(MatchCheckErr::NotImplemented); | ||
376 | } | ||
377 | |||
378 | Some(self.replace_head_with(pat_ids.iter())) | ||
379 | } | ||
380 | (Pat::Lit(lit_expr), Constructor::Bool(constructor_val)) => { | ||
381 | match cx.body.exprs[lit_expr] { | ||
382 | Expr::Literal(Literal::Bool(pat_val)) if *constructor_val == pat_val => { | ||
383 | Some(self.to_tail()) | ||
384 | } | ||
385 | // it was a bool but the value doesn't match | ||
386 | Expr::Literal(Literal::Bool(_)) => None, | ||
387 | // perhaps this is actually unreachable given we have | ||
388 | // already checked that these match arms have the appropriate type? | ||
389 | _ => return Err(MatchCheckErr::NotImplemented), | ||
390 | } | ||
391 | } | ||
392 | (Pat::Wild, constructor) => Some(self.expand_wildcard(cx, constructor)?), | ||
393 | (Pat::Path(_), Constructor::Enum(constructor)) => { | ||
394 | // unit enum variants become `Pat::Path` | ||
395 | let pat_id = head.as_id().expect("we know this isn't a wild"); | ||
396 | if !enum_variant_matches(cx, pat_id, *constructor) { | ||
397 | None | ||
398 | } else { | ||
399 | Some(self.to_tail()) | ||
400 | } | ||
401 | } | ||
402 | ( | ||
403 | Pat::TupleStruct { args: ref pat_ids, ellipsis, .. }, | ||
404 | Constructor::Enum(enum_constructor), | ||
405 | ) => { | ||
406 | let pat_id = head.as_id().expect("we know this isn't a wild"); | ||
407 | if !enum_variant_matches(cx, pat_id, *enum_constructor) { | ||
408 | None | ||
409 | } else { | ||
410 | let constructor_arity = constructor.arity(cx)?; | ||
411 | if let Some(ellipsis_position) = ellipsis { | ||
412 | // If there are ellipsis in the pattern, the ellipsis must take the place | ||
413 | // of at least one sub-pattern, so `pat_ids` should be smaller than the | ||
414 | // constructor arity. | ||
415 | if pat_ids.len() < constructor_arity { | ||
416 | let mut new_patterns: Vec<PatIdOrWild> = vec![]; | ||
417 | |||
418 | for pat_id in &pat_ids[0..ellipsis_position] { | ||
419 | new_patterns.push((*pat_id).into()); | ||
420 | } | ||
421 | |||
422 | for _ in 0..(constructor_arity - pat_ids.len()) { | ||
423 | new_patterns.push(PatIdOrWild::Wild); | ||
424 | } | ||
425 | |||
426 | for pat_id in &pat_ids[ellipsis_position..pat_ids.len()] { | ||
427 | new_patterns.push((*pat_id).into()); | ||
428 | } | ||
429 | |||
430 | Some(self.replace_head_with(new_patterns.into_iter())) | ||
431 | } else { | ||
432 | return Err(MatchCheckErr::MalformedMatchArm); | ||
433 | } | ||
434 | } else { | ||
435 | // If there is no ellipsis in the tuple pattern, the number | ||
436 | // of patterns must equal the constructor arity. | ||
437 | if pat_ids.len() == constructor_arity { | ||
438 | Some(self.replace_head_with(pat_ids.into_iter())) | ||
439 | } else { | ||
440 | return Err(MatchCheckErr::MalformedMatchArm); | ||
441 | } | ||
442 | } | ||
443 | } | ||
444 | } | ||
445 | (Pat::Record { args: ref arg_patterns, .. }, Constructor::Enum(e)) => { | ||
446 | let pat_id = head.as_id().expect("we know this isn't a wild"); | ||
447 | if !enum_variant_matches(cx, pat_id, *e) { | ||
448 | None | ||
449 | } else { | ||
450 | match cx.db.enum_data(e.parent).variants[e.local_id].variant_data.as_ref() { | ||
451 | VariantData::Record(struct_field_arena) => { | ||
452 | // Here we treat any missing fields in the record as the wild pattern, as | ||
453 | // if the record has ellipsis. We want to do this here even if the | ||
454 | // record does not contain ellipsis, because it allows us to continue | ||
455 | // enforcing exhaustiveness for the rest of the match statement. | ||
456 | // | ||
457 | // Creating the diagnostic for the missing field in the pattern | ||
458 | // should be done in a different diagnostic. | ||
459 | let patterns = struct_field_arena.iter().map(|(_, struct_field)| { | ||
460 | arg_patterns | ||
461 | .iter() | ||
462 | .find(|pat| pat.name == struct_field.name) | ||
463 | .map(|pat| PatIdOrWild::from(pat.pat)) | ||
464 | .unwrap_or(PatIdOrWild::Wild) | ||
465 | }); | ||
466 | |||
467 | Some(self.replace_head_with(patterns)) | ||
468 | } | ||
469 | _ => return Err(MatchCheckErr::Unknown), | ||
470 | } | ||
471 | } | ||
472 | } | ||
473 | (Pat::Or(_), _) => return Err(MatchCheckErr::NotImplemented), | ||
474 | (_, _) => return Err(MatchCheckErr::NotImplemented), | ||
475 | }; | ||
476 | |||
477 | Ok(result) | ||
478 | } | ||
479 | |||
480 | /// A special case of `specialize_constructor` where the head of the pattern stack | ||
481 | /// is a Wild pattern. | ||
482 | /// | ||
483 | /// Replaces the Wild pattern at the head of the pattern stack with N Wild patterns | ||
484 | /// (N >= 0), where N is the arity of the given constructor. | ||
485 | fn expand_wildcard( | ||
486 | &self, | ||
487 | cx: &MatchCheckCtx, | ||
488 | constructor: &Constructor, | ||
489 | ) -> MatchCheckResult<PatStack> { | ||
490 | assert_eq!( | ||
491 | Pat::Wild, | ||
492 | self.get_head().expect("expand_wildcard called on empty PatStack").as_pat(cx), | ||
493 | "expand_wildcard must only be called on PatStack with wild at head", | ||
494 | ); | ||
495 | |||
496 | let mut patterns: PatStackInner = smallvec![]; | ||
497 | |||
498 | for _ in 0..constructor.arity(cx)? { | ||
499 | patterns.push(PatIdOrWild::Wild); | ||
500 | } | ||
501 | |||
502 | for pat in &self.0[1..] { | ||
503 | patterns.push(*pat); | ||
504 | } | ||
505 | |||
506 | Ok(PatStack::from_vec(patterns)) | ||
507 | } | ||
508 | } | ||
509 | |||
510 | /// A collection of PatStack. | ||
511 | /// | ||
512 | /// This type is modeled from the struct of the same name in `rustc`. | ||
513 | pub(super) struct Matrix(Vec<PatStack>); | ||
514 | |||
515 | impl Matrix { | ||
516 | pub(super) fn empty() -> Self { | ||
517 | Self(vec![]) | ||
518 | } | ||
519 | |||
520 | pub(super) fn push(&mut self, cx: &MatchCheckCtx, row: PatStack) { | ||
521 | if let Some(Pat::Or(pat_ids)) = row.get_head().map(|pat_id| pat_id.as_pat(cx)) { | ||
522 | // Or patterns are expanded here | ||
523 | for pat_id in pat_ids { | ||
524 | self.0.push(PatStack::from_pattern(pat_id)); | ||
525 | } | ||
526 | } else { | ||
527 | self.0.push(row); | ||
528 | } | ||
529 | } | ||
530 | |||
531 | fn is_empty(&self) -> bool { | ||
532 | self.0.is_empty() | ||
533 | } | ||
534 | |||
535 | fn heads(&self) -> Vec<PatIdOrWild> { | ||
536 | self.0.iter().flat_map(|p| p.get_head()).collect() | ||
537 | } | ||
538 | |||
539 | /// Computes `D(self)` for each contained PatStack. | ||
540 | /// | ||
541 | /// See the module docs and the associated documentation in rustc for details. | ||
542 | fn specialize_wildcard(&self, cx: &MatchCheckCtx) -> Self { | ||
543 | Self::collect(cx, self.0.iter().filter_map(|r| r.specialize_wildcard(cx))) | ||
544 | } | ||
545 | |||
546 | /// Computes `S(constructor, self)` for each contained PatStack. | ||
547 | /// | ||
548 | /// See the module docs and the associated documentation in rustc for details. | ||
549 | fn specialize_constructor( | ||
550 | &self, | ||
551 | cx: &MatchCheckCtx, | ||
552 | constructor: &Constructor, | ||
553 | ) -> MatchCheckResult<Self> { | ||
554 | let mut new_matrix = Matrix::empty(); | ||
555 | for pat in &self.0 { | ||
556 | if let Some(pat) = pat.specialize_constructor(cx, constructor)? { | ||
557 | new_matrix.push(cx, pat); | ||
558 | } | ||
559 | } | ||
560 | |||
561 | Ok(new_matrix) | ||
562 | } | ||
563 | |||
564 | fn collect<T: IntoIterator<Item = PatStack>>(cx: &MatchCheckCtx, iter: T) -> Self { | ||
565 | let mut matrix = Matrix::empty(); | ||
566 | |||
567 | for pat in iter { | ||
568 | // using push ensures we expand or-patterns | ||
569 | matrix.push(cx, pat); | ||
570 | } | ||
571 | |||
572 | matrix | ||
573 | } | ||
574 | } | ||
575 | |||
576 | #[derive(Clone, Debug, PartialEq)] | ||
577 | /// An indication of the usefulness of a given match arm, where | ||
578 | /// usefulness is defined as matching some patterns which were | ||
579 | /// not matched by an prior match arms. | ||
580 | /// | ||
581 | /// We may eventually need an `Unknown` variant here. | ||
582 | pub(super) enum Usefulness { | ||
583 | Useful, | ||
584 | NotUseful, | ||
585 | } | ||
586 | |||
587 | pub(super) struct MatchCheckCtx<'a> { | ||
588 | pub(super) match_expr: Idx<Expr>, | ||
589 | pub(super) body: Arc<Body>, | ||
590 | pub(super) infer: Arc<InferenceResult>, | ||
591 | pub(super) db: &'a dyn HirDatabase, | ||
592 | } | ||
593 | |||
594 | /// Given a set of patterns `matrix`, and pattern to consider `v`, determines | ||
595 | /// whether `v` is useful. A pattern is useful if it covers cases which were | ||
596 | /// not previously covered. | ||
597 | /// | ||
598 | /// When calling this function externally (that is, not the recursive calls) it | ||
599 | /// expected that you have already type checked the match arms. All patterns in | ||
600 | /// matrix should be the same type as v, as well as they should all be the same | ||
601 | /// type as the match expression. | ||
602 | pub(super) fn is_useful( | ||
603 | cx: &MatchCheckCtx, | ||
604 | matrix: &Matrix, | ||
605 | v: &PatStack, | ||
606 | ) -> MatchCheckResult<Usefulness> { | ||
607 | // Handle two special cases: | ||
608 | // - enum with no variants | ||
609 | // - `!` type | ||
610 | // In those cases, no match arm is useful. | ||
611 | match cx.infer[cx.match_expr].strip_references() { | ||
612 | Ty::Apply(ApplicationTy { ctor: TypeCtor::Adt(AdtId::EnumId(enum_id)), .. }) => { | ||
613 | if cx.db.enum_data(*enum_id).variants.is_empty() { | ||
614 | return Ok(Usefulness::NotUseful); | ||
615 | } | ||
616 | } | ||
617 | Ty::Apply(ApplicationTy { ctor: TypeCtor::Never, .. }) => { | ||
618 | return Ok(Usefulness::NotUseful); | ||
619 | } | ||
620 | _ => (), | ||
621 | } | ||
622 | |||
623 | let head = match v.get_head() { | ||
624 | Some(head) => head, | ||
625 | None => { | ||
626 | let result = if matrix.is_empty() { Usefulness::Useful } else { Usefulness::NotUseful }; | ||
627 | |||
628 | return Ok(result); | ||
629 | } | ||
630 | }; | ||
631 | |||
632 | if let Pat::Or(pat_ids) = head.as_pat(cx) { | ||
633 | let mut found_unimplemented = false; | ||
634 | let any_useful = pat_ids.iter().any(|&pat_id| { | ||
635 | let v = PatStack::from_pattern(pat_id); | ||
636 | |||
637 | match is_useful(cx, matrix, &v) { | ||
638 | Ok(Usefulness::Useful) => true, | ||
639 | Ok(Usefulness::NotUseful) => false, | ||
640 | _ => { | ||
641 | found_unimplemented = true; | ||
642 | false | ||
643 | } | ||
644 | } | ||
645 | }); | ||
646 | |||
647 | return if any_useful { | ||
648 | Ok(Usefulness::Useful) | ||
649 | } else if found_unimplemented { | ||
650 | Err(MatchCheckErr::NotImplemented) | ||
651 | } else { | ||
652 | Ok(Usefulness::NotUseful) | ||
653 | }; | ||
654 | } | ||
655 | |||
656 | if let Some(constructor) = pat_constructor(cx, head)? { | ||
657 | let matrix = matrix.specialize_constructor(&cx, &constructor)?; | ||
658 | let v = v | ||
659 | .specialize_constructor(&cx, &constructor)? | ||
660 | .expect("we know this can't fail because we get the constructor from `v.head()` above"); | ||
661 | |||
662 | is_useful(&cx, &matrix, &v) | ||
663 | } else { | ||
664 | // expanding wildcard | ||
665 | let mut used_constructors: Vec<Constructor> = vec![]; | ||
666 | for pat in matrix.heads() { | ||
667 | if let Some(constructor) = pat_constructor(cx, pat)? { | ||
668 | used_constructors.push(constructor); | ||
669 | } | ||
670 | } | ||
671 | |||
672 | // We assume here that the first constructor is the "correct" type. Since we | ||
673 | // only care about the "type" of the constructor (i.e. if it is a bool we | ||
674 | // don't care about the value), this assumption should be valid as long as | ||
675 | // the match statement is well formed. We currently uphold this invariant by | ||
676 | // filtering match arms before calling `is_useful`, only passing in match arms | ||
677 | // whose type matches the type of the match expression. | ||
678 | match &used_constructors.first() { | ||
679 | Some(constructor) if all_constructors_covered(&cx, constructor, &used_constructors) => { | ||
680 | // If all constructors are covered, then we need to consider whether | ||
681 | // any values are covered by this wildcard. | ||
682 | // | ||
683 | // For example, with matrix '[[Some(true)], [None]]', all | ||
684 | // constructors are covered (`Some`/`None`), so we need | ||
685 | // to perform specialization to see that our wildcard will cover | ||
686 | // the `Some(false)` case. | ||
687 | // | ||
688 | // Here we create a constructor for each variant and then check | ||
689 | // usefulness after specializing for that constructor. | ||
690 | let mut found_unimplemented = false; | ||
691 | for constructor in constructor.all_constructors(cx) { | ||
692 | let matrix = matrix.specialize_constructor(&cx, &constructor)?; | ||
693 | let v = v.expand_wildcard(&cx, &constructor)?; | ||
694 | |||
695 | match is_useful(&cx, &matrix, &v) { | ||
696 | Ok(Usefulness::Useful) => return Ok(Usefulness::Useful), | ||
697 | Ok(Usefulness::NotUseful) => continue, | ||
698 | _ => found_unimplemented = true, | ||
699 | }; | ||
700 | } | ||
701 | |||
702 | if found_unimplemented { | ||
703 | Err(MatchCheckErr::NotImplemented) | ||
704 | } else { | ||
705 | Ok(Usefulness::NotUseful) | ||
706 | } | ||
707 | } | ||
708 | _ => { | ||
709 | // Either not all constructors are covered, or the only other arms | ||
710 | // are wildcards. Either way, this pattern is useful if it is useful | ||
711 | // when compared to those arms with wildcards. | ||
712 | let matrix = matrix.specialize_wildcard(&cx); | ||
713 | let v = v.to_tail(); | ||
714 | |||
715 | is_useful(&cx, &matrix, &v) | ||
716 | } | ||
717 | } | ||
718 | } | ||
719 | } | ||
720 | |||
721 | #[derive(Debug, Clone, Copy)] | ||
722 | /// Similar to TypeCtor, but includes additional information about the specific | ||
723 | /// value being instantiated. For example, TypeCtor::Bool doesn't contain the | ||
724 | /// boolean value. | ||
725 | enum Constructor { | ||
726 | Bool(bool), | ||
727 | Tuple { arity: usize }, | ||
728 | Enum(EnumVariantId), | ||
729 | } | ||
730 | |||
731 | impl Constructor { | ||
732 | fn arity(&self, cx: &MatchCheckCtx) -> MatchCheckResult<usize> { | ||
733 | let arity = match self { | ||
734 | Constructor::Bool(_) => 0, | ||
735 | Constructor::Tuple { arity } => *arity, | ||
736 | Constructor::Enum(e) => { | ||
737 | match cx.db.enum_data(e.parent).variants[e.local_id].variant_data.as_ref() { | ||
738 | VariantData::Tuple(struct_field_data) => struct_field_data.len(), | ||
739 | VariantData::Record(struct_field_data) => struct_field_data.len(), | ||
740 | VariantData::Unit => 0, | ||
741 | } | ||
742 | } | ||
743 | }; | ||
744 | |||
745 | Ok(arity) | ||
746 | } | ||
747 | |||
748 | fn all_constructors(&self, cx: &MatchCheckCtx) -> Vec<Constructor> { | ||
749 | match self { | ||
750 | Constructor::Bool(_) => vec![Constructor::Bool(true), Constructor::Bool(false)], | ||
751 | Constructor::Tuple { .. } => vec![*self], | ||
752 | Constructor::Enum(e) => cx | ||
753 | .db | ||
754 | .enum_data(e.parent) | ||
755 | .variants | ||
756 | .iter() | ||
757 | .map(|(local_id, _)| { | ||
758 | Constructor::Enum(EnumVariantId { parent: e.parent, local_id }) | ||
759 | }) | ||
760 | .collect(), | ||
761 | } | ||
762 | } | ||
763 | } | ||
764 | |||
765 | /// Returns the constructor for the given pattern. Should only return None | ||
766 | /// in the case of a Wild pattern. | ||
767 | fn pat_constructor(cx: &MatchCheckCtx, pat: PatIdOrWild) -> MatchCheckResult<Option<Constructor>> { | ||
768 | let res = match pat.as_pat(cx) { | ||
769 | Pat::Wild => None, | ||
770 | // FIXME somehow create the Tuple constructor with the proper arity. If there are | ||
771 | // ellipsis, the arity is not equal to the number of patterns. | ||
772 | Pat::Tuple { args: pats, ellipsis } if ellipsis.is_none() => { | ||
773 | Some(Constructor::Tuple { arity: pats.len() }) | ||
774 | } | ||
775 | Pat::Lit(lit_expr) => match cx.body.exprs[lit_expr] { | ||
776 | Expr::Literal(Literal::Bool(val)) => Some(Constructor::Bool(val)), | ||
777 | _ => return Err(MatchCheckErr::NotImplemented), | ||
778 | }, | ||
779 | Pat::TupleStruct { .. } | Pat::Path(_) | Pat::Record { .. } => { | ||
780 | let pat_id = pat.as_id().expect("we already know this pattern is not a wild"); | ||
781 | let variant_id = | ||
782 | cx.infer.variant_resolution_for_pat(pat_id).ok_or(MatchCheckErr::Unknown)?; | ||
783 | match variant_id { | ||
784 | VariantId::EnumVariantId(enum_variant_id) => { | ||
785 | Some(Constructor::Enum(enum_variant_id)) | ||
786 | } | ||
787 | _ => return Err(MatchCheckErr::NotImplemented), | ||
788 | } | ||
789 | } | ||
790 | _ => return Err(MatchCheckErr::NotImplemented), | ||
791 | }; | ||
792 | |||
793 | Ok(res) | ||
794 | } | ||
795 | |||
796 | fn all_constructors_covered( | ||
797 | cx: &MatchCheckCtx, | ||
798 | constructor: &Constructor, | ||
799 | used_constructors: &[Constructor], | ||
800 | ) -> bool { | ||
801 | match constructor { | ||
802 | Constructor::Tuple { arity } => { | ||
803 | used_constructors.iter().any(|constructor| match constructor { | ||
804 | Constructor::Tuple { arity: used_arity } => arity == used_arity, | ||
805 | _ => false, | ||
806 | }) | ||
807 | } | ||
808 | Constructor::Bool(_) => { | ||
809 | if used_constructors.is_empty() { | ||
810 | return false; | ||
811 | } | ||
812 | |||
813 | let covers_true = | ||
814 | used_constructors.iter().any(|c| matches!(c, Constructor::Bool(true))); | ||
815 | let covers_false = | ||
816 | used_constructors.iter().any(|c| matches!(c, Constructor::Bool(false))); | ||
817 | |||
818 | covers_true && covers_false | ||
819 | } | ||
820 | Constructor::Enum(e) => cx.db.enum_data(e.parent).variants.iter().all(|(id, _)| { | ||
821 | for constructor in used_constructors { | ||
822 | if let Constructor::Enum(e) = constructor { | ||
823 | if id == e.local_id { | ||
824 | return true; | ||
825 | } | ||
826 | } | ||
827 | } | ||
828 | |||
829 | false | ||
830 | }), | ||
831 | } | ||
832 | } | ||
833 | |||
834 | fn enum_variant_matches(cx: &MatchCheckCtx, pat_id: PatId, enum_variant_id: EnumVariantId) -> bool { | ||
835 | Some(enum_variant_id.into()) == cx.infer.variant_resolution_for_pat(pat_id) | ||
836 | } | ||
837 | |||
838 | #[cfg(test)] | ||
839 | mod tests { | ||
840 | use crate::diagnostics::tests::check_diagnostics; | ||
841 | |||
842 | #[test] | ||
843 | fn empty_tuple() { | ||
844 | check_diagnostics( | ||
845 | r#" | ||
846 | fn main() { | ||
847 | match () { } | ||
848 | //^^ Missing match arm | ||
849 | match (()) { } | ||
850 | //^^^^ Missing match arm | ||
851 | |||
852 | match () { _ => (), } | ||
853 | match () { () => (), } | ||
854 | match (()) { (()) => (), } | ||
855 | } | ||
856 | "#, | ||
857 | ); | ||
858 | } | ||
859 | |||
860 | #[test] | ||
861 | fn tuple_of_two_empty_tuple() { | ||
862 | check_diagnostics( | ||
863 | r#" | ||
864 | fn main() { | ||
865 | match ((), ()) { } | ||
866 | //^^^^^^^^ Missing match arm | ||
867 | |||
868 | match ((), ()) { ((), ()) => (), } | ||
869 | } | ||
870 | "#, | ||
871 | ); | ||
872 | } | ||
873 | |||
874 | #[test] | ||
875 | fn boolean() { | ||
876 | check_diagnostics( | ||
877 | r#" | ||
878 | fn test_main() { | ||
879 | match false { } | ||
880 | //^^^^^ Missing match arm | ||
881 | match false { true => (), } | ||
882 | //^^^^^ Missing match arm | ||
883 | match (false, true) {} | ||
884 | //^^^^^^^^^^^^^ Missing match arm | ||
885 | match (false, true) { (true, true) => (), } | ||
886 | //^^^^^^^^^^^^^ Missing match arm | ||
887 | match (false, true) { | ||
888 | //^^^^^^^^^^^^^ Missing match arm | ||
889 | (false, true) => (), | ||
890 | (false, false) => (), | ||
891 | (true, false) => (), | ||
892 | } | ||
893 | match (false, true) { (true, _x) => (), } | ||
894 | //^^^^^^^^^^^^^ Missing match arm | ||
895 | |||
896 | match false { true => (), false => (), } | ||
897 | match (false, true) { | ||
898 | (false, _) => (), | ||
899 | (true, false) => (), | ||
900 | (_, true) => (), | ||
901 | } | ||
902 | match (false, true) { | ||
903 | (true, true) => (), | ||
904 | (true, false) => (), | ||
905 | (false, true) => (), | ||
906 | (false, false) => (), | ||
907 | } | ||
908 | match (false, true) { | ||
909 | (true, _x) => (), | ||
910 | (false, true) => (), | ||
911 | (false, false) => (), | ||
912 | } | ||
913 | match (false, true, false) { | ||
914 | (false, ..) => (), | ||
915 | (true, ..) => (), | ||
916 | } | ||
917 | match (false, true, false) { | ||
918 | (.., false) => (), | ||
919 | (.., true) => (), | ||
920 | } | ||
921 | match (false, true, false) { (..) => (), } | ||
922 | } | ||
923 | "#, | ||
924 | ); | ||
925 | } | ||
926 | |||
927 | #[test] | ||
928 | fn tuple_of_tuple_and_bools() { | ||
929 | check_diagnostics( | ||
930 | r#" | ||
931 | fn main() { | ||
932 | match (false, ((), false)) {} | ||
933 | //^^^^^^^^^^^^^^^^^^^^ Missing match arm | ||
934 | match (false, ((), false)) { (true, ((), true)) => (), } | ||
935 | //^^^^^^^^^^^^^^^^^^^^ Missing match arm | ||
936 | match (false, ((), false)) { (true, _) => (), } | ||
937 | //^^^^^^^^^^^^^^^^^^^^ Missing match arm | ||
938 | |||
939 | match (false, ((), false)) { | ||
940 | (true, ((), true)) => (), | ||
941 | (true, ((), false)) => (), | ||
942 | (false, ((), true)) => (), | ||
943 | (false, ((), false)) => (), | ||
944 | } | ||
945 | match (false, ((), false)) { | ||
946 | (true, ((), true)) => (), | ||
947 | (true, ((), false)) => (), | ||
948 | (false, _) => (), | ||
949 | } | ||
950 | } | ||
951 | "#, | ||
952 | ); | ||
953 | } | ||
954 | |||
955 | #[test] | ||
956 | fn enums() { | ||
957 | check_diagnostics( | ||
958 | r#" | ||
959 | enum Either { A, B, } | ||
960 | |||
961 | fn main() { | ||
962 | match Either::A { } | ||
963 | //^^^^^^^^^ Missing match arm | ||
964 | match Either::B { Either::A => (), } | ||
965 | //^^^^^^^^^ Missing match arm | ||
966 | |||
967 | match &Either::B { | ||
968 | //^^^^^^^^^^ Missing match arm | ||
969 | Either::A => (), | ||
970 | } | ||
971 | |||
972 | match Either::B { | ||
973 | Either::A => (), Either::B => (), | ||
974 | } | ||
975 | match &Either::B { | ||
976 | Either::A => (), Either::B => (), | ||
977 | } | ||
978 | } | ||
979 | "#, | ||
980 | ); | ||
981 | } | ||
982 | |||
983 | #[test] | ||
984 | fn enum_containing_bool() { | ||
985 | check_diagnostics( | ||
986 | r#" | ||
987 | enum Either { A(bool), B } | ||
988 | |||
989 | fn main() { | ||
990 | match Either::B { } | ||
991 | //^^^^^^^^^ Missing match arm | ||
992 | match Either::B { | ||
993 | //^^^^^^^^^ Missing match arm | ||
994 | Either::A(true) => (), Either::B => () | ||
995 | } | ||
996 | |||
997 | match Either::B { | ||
998 | Either::A(true) => (), | ||
999 | Either::A(false) => (), | ||
1000 | Either::B => (), | ||
1001 | } | ||
1002 | match Either::B { | ||
1003 | Either::B => (), | ||
1004 | _ => (), | ||
1005 | } | ||
1006 | match Either::B { | ||
1007 | Either::A(_) => (), | ||
1008 | Either::B => (), | ||
1009 | } | ||
1010 | |||
1011 | } | ||
1012 | "#, | ||
1013 | ); | ||
1014 | } | ||
1015 | |||
1016 | #[test] | ||
1017 | fn enum_different_sizes() { | ||
1018 | check_diagnostics( | ||
1019 | r#" | ||
1020 | enum Either { A(bool), B(bool, bool) } | ||
1021 | |||
1022 | fn main() { | ||
1023 | match Either::A(false) { | ||
1024 | //^^^^^^^^^^^^^^^^ Missing match arm | ||
1025 | Either::A(_) => (), | ||
1026 | Either::B(false, _) => (), | ||
1027 | } | ||
1028 | |||
1029 | match Either::A(false) { | ||
1030 | Either::A(_) => (), | ||
1031 | Either::B(true, _) => (), | ||
1032 | Either::B(false, _) => (), | ||
1033 | } | ||
1034 | match Either::A(false) { | ||
1035 | Either::A(true) | Either::A(false) => (), | ||
1036 | Either::B(true, _) => (), | ||
1037 | Either::B(false, _) => (), | ||
1038 | } | ||
1039 | } | ||
1040 | "#, | ||
1041 | ); | ||
1042 | } | ||
1043 | |||
1044 | #[test] | ||
1045 | fn tuple_of_enum_no_diagnostic() { | ||
1046 | check_diagnostics( | ||
1047 | r#" | ||
1048 | enum Either { A(bool), B(bool, bool) } | ||
1049 | enum Either2 { C, D } | ||
1050 | |||
1051 | fn main() { | ||
1052 | match (Either::A(false), Either2::C) { | ||
1053 | (Either::A(true), _) | (Either::A(false), _) => (), | ||
1054 | (Either::B(true, _), Either2::C) => (), | ||
1055 | (Either::B(false, _), Either2::C) => (), | ||
1056 | (Either::B(_, _), Either2::D) => (), | ||
1057 | } | ||
1058 | } | ||
1059 | "#, | ||
1060 | ); | ||
1061 | } | ||
1062 | |||
1063 | #[test] | ||
1064 | fn mismatched_types() { | ||
1065 | // Match statements with arms that don't match the | ||
1066 | // expression pattern do not fire this diagnostic. | ||
1067 | check_diagnostics( | ||
1068 | r#" | ||
1069 | enum Either { A, B } | ||
1070 | enum Either2 { C, D } | ||
1071 | |||
1072 | fn main() { | ||
1073 | match Either::A { | ||
1074 | Either2::C => (), | ||
1075 | Either2::D => (), | ||
1076 | } | ||
1077 | match (true, false) { | ||
1078 | (true, false, true) => (), | ||
1079 | (true) => (), | ||
1080 | } | ||
1081 | match (0) { () => () } | ||
1082 | match Unresolved::Bar { Unresolved::Baz => () } | ||
1083 | } | ||
1084 | "#, | ||
1085 | ); | ||
1086 | } | ||
1087 | |||
1088 | #[test] | ||
1089 | fn malformed_match_arm_tuple_enum_missing_pattern() { | ||
1090 | // We are testing to be sure we don't panic here when the match | ||
1091 | // arm `Either::B` is missing its pattern. | ||
1092 | check_diagnostics( | ||
1093 | r#" | ||
1094 | enum Either { A, B(u32) } | ||
1095 | |||
1096 | fn main() { | ||
1097 | match Either::A { | ||
1098 | Either::A => (), | ||
1099 | Either::B() => (), | ||
1100 | } | ||
1101 | } | ||
1102 | "#, | ||
1103 | ); | ||
1104 | } | ||
1105 | |||
1106 | #[test] | ||
1107 | fn expr_diverges() { | ||
1108 | check_diagnostics( | ||
1109 | r#" | ||
1110 | enum Either { A, B } | ||
1111 | |||
1112 | fn main() { | ||
1113 | match loop {} { | ||
1114 | Either::A => (), | ||
1115 | Either::B => (), | ||
1116 | } | ||
1117 | match loop {} { | ||
1118 | Either::A => (), | ||
1119 | } | ||
1120 | match loop { break Foo::A } { | ||
1121 | //^^^^^^^^^^^^^^^^^^^^^ Missing match arm | ||
1122 | Either::A => (), | ||
1123 | } | ||
1124 | match loop { break Foo::A } { | ||
1125 | Either::A => (), | ||
1126 | Either::B => (), | ||
1127 | } | ||
1128 | } | ||
1129 | "#, | ||
1130 | ); | ||
1131 | } | ||
1132 | |||
1133 | #[test] | ||
1134 | fn expr_partially_diverges() { | ||
1135 | check_diagnostics( | ||
1136 | r#" | ||
1137 | enum Either<T> { A(T), B } | ||
1138 | |||
1139 | fn foo() -> Either<!> { Either::B } | ||
1140 | fn main() -> u32 { | ||
1141 | match foo() { | ||
1142 | Either::A(val) => val, | ||
1143 | Either::B => 0, | ||
1144 | } | ||
1145 | } | ||
1146 | "#, | ||
1147 | ); | ||
1148 | } | ||
1149 | |||
1150 | #[test] | ||
1151 | fn enum_record() { | ||
1152 | check_diagnostics( | ||
1153 | r#" | ||
1154 | enum Either { A { foo: bool }, B } | ||
1155 | |||
1156 | fn main() { | ||
1157 | let a = Either::A { foo: true }; | ||
1158 | match a { } | ||
1159 | //^ Missing match arm | ||
1160 | match a { Either::A { foo: true } => () } | ||
1161 | //^ Missing match arm | ||
1162 | match a { | ||
1163 | Either::A { } => (), | ||
1164 | //^^^^^^^^^ Missing structure fields: | ||
1165 | // | - foo | ||
1166 | Either::B => (), | ||
1167 | } | ||
1168 | match a { | ||
1169 | //^ Missing match arm | ||
1170 | Either::A { } => (), | ||
1171 | } //^^^^^^^^^ Missing structure fields: | ||
1172 | // | - foo | ||
1173 | |||
1174 | match a { | ||
1175 | Either::A { foo: true } => (), | ||
1176 | Either::A { foo: false } => (), | ||
1177 | Either::B => (), | ||
1178 | } | ||
1179 | match a { | ||
1180 | Either::A { foo: _ } => (), | ||
1181 | Either::B => (), | ||
1182 | } | ||
1183 | } | ||
1184 | "#, | ||
1185 | ); | ||
1186 | } | ||
1187 | |||
1188 | #[test] | ||
1189 | fn enum_record_fields_out_of_order() { | ||
1190 | check_diagnostics( | ||
1191 | r#" | ||
1192 | enum Either { | ||
1193 | A { foo: bool, bar: () }, | ||
1194 | B, | ||
1195 | } | ||
1196 | |||
1197 | fn main() { | ||
1198 | let a = Either::A { foo: true, bar: () }; | ||
1199 | match a { | ||
1200 | //^ Missing match arm | ||
1201 | Either::A { bar: (), foo: false } => (), | ||
1202 | Either::A { foo: true, bar: () } => (), | ||
1203 | } | ||
1204 | |||
1205 | match a { | ||
1206 | Either::A { bar: (), foo: false } => (), | ||
1207 | Either::A { foo: true, bar: () } => (), | ||
1208 | Either::B => (), | ||
1209 | } | ||
1210 | } | ||
1211 | "#, | ||
1212 | ); | ||
1213 | } | ||
1214 | |||
1215 | #[test] | ||
1216 | fn enum_record_ellipsis() { | ||
1217 | check_diagnostics( | ||
1218 | r#" | ||
1219 | enum Either { | ||
1220 | A { foo: bool, bar: bool }, | ||
1221 | B, | ||
1222 | } | ||
1223 | |||
1224 | fn main() { | ||
1225 | let a = Either::B; | ||
1226 | match a { | ||
1227 | //^ Missing match arm | ||
1228 | Either::A { foo: true, .. } => (), | ||
1229 | Either::B => (), | ||
1230 | } | ||
1231 | match a { | ||
1232 | //^ Missing match arm | ||
1233 | Either::A { .. } => (), | ||
1234 | } | ||
1235 | |||
1236 | match a { | ||
1237 | Either::A { foo: true, .. } => (), | ||
1238 | Either::A { foo: false, .. } => (), | ||
1239 | Either::B => (), | ||
1240 | } | ||
1241 | |||
1242 | match a { | ||
1243 | Either::A { .. } => (), | ||
1244 | Either::B => (), | ||
1245 | } | ||
1246 | } | ||
1247 | "#, | ||
1248 | ); | ||
1249 | } | ||
1250 | |||
1251 | #[test] | ||
1252 | fn enum_tuple_partial_ellipsis() { | ||
1253 | check_diagnostics( | ||
1254 | r#" | ||
1255 | enum Either { | ||
1256 | A(bool, bool, bool, bool), | ||
1257 | B, | ||
1258 | } | ||
1259 | |||
1260 | fn main() { | ||
1261 | match Either::B { | ||
1262 | //^^^^^^^^^ Missing match arm | ||
1263 | Either::A(true, .., true) => (), | ||
1264 | Either::A(true, .., false) => (), | ||
1265 | Either::A(false, .., false) => (), | ||
1266 | Either::B => (), | ||
1267 | } | ||
1268 | match Either::B { | ||
1269 | //^^^^^^^^^ Missing match arm | ||
1270 | Either::A(true, .., true) => (), | ||
1271 | Either::A(true, .., false) => (), | ||
1272 | Either::A(.., true) => (), | ||
1273 | Either::B => (), | ||
1274 | } | ||
1275 | |||
1276 | match Either::B { | ||
1277 | Either::A(true, .., true) => (), | ||
1278 | Either::A(true, .., false) => (), | ||
1279 | Either::A(false, .., true) => (), | ||
1280 | Either::A(false, .., false) => (), | ||
1281 | Either::B => (), | ||
1282 | } | ||
1283 | match Either::B { | ||
1284 | Either::A(true, .., true) => (), | ||
1285 | Either::A(true, .., false) => (), | ||
1286 | Either::A(.., true) => (), | ||
1287 | Either::A(.., false) => (), | ||
1288 | Either::B => (), | ||
1289 | } | ||
1290 | } | ||
1291 | "#, | ||
1292 | ); | ||
1293 | } | ||
1294 | |||
1295 | #[test] | ||
1296 | fn never() { | ||
1297 | check_diagnostics( | ||
1298 | r#" | ||
1299 | enum Never {} | ||
1300 | |||
1301 | fn enum_(never: Never) { | ||
1302 | match never {} | ||
1303 | } | ||
1304 | fn enum_ref(never: &Never) { | ||
1305 | match never {} | ||
1306 | } | ||
1307 | fn bang(never: !) { | ||
1308 | match never {} | ||
1309 | } | ||
1310 | "#, | ||
1311 | ); | ||
1312 | } | ||
1313 | |||
1314 | #[test] | ||
1315 | fn or_pattern_panic() { | ||
1316 | check_diagnostics( | ||
1317 | r#" | ||
1318 | pub enum Category { Infinity, Zero } | ||
1319 | |||
1320 | fn panic(a: Category, b: Category) { | ||
1321 | match (a, b) { | ||
1322 | (Category::Zero | Category::Infinity, _) => (), | ||
1323 | (_, Category::Zero | Category::Infinity) => (), | ||
1324 | } | ||
1325 | |||
1326 | // FIXME: This is a false positive, but the code used to cause a panic in the match checker, | ||
1327 | // so this acts as a regression test for that. | ||
1328 | match (a, b) { | ||
1329 | //^^^^^^ Missing match arm | ||
1330 | (Category::Infinity, Category::Infinity) | (Category::Zero, Category::Zero) => (), | ||
1331 | (Category::Infinity | Category::Zero, _) => (), | ||
1332 | } | ||
1333 | } | ||
1334 | "#, | ||
1335 | ); | ||
1336 | } | ||
1337 | |||
1338 | mod false_negatives { | ||
1339 | //! The implementation of match checking here is a work in progress. As we roll this out, we | ||
1340 | //! prefer false negatives to false positives (ideally there would be no false positives). This | ||
1341 | //! test module should document known false negatives. Eventually we will have a complete | ||
1342 | //! implementation of match checking and this module will be empty. | ||
1343 | //! | ||
1344 | //! The reasons for documenting known false negatives: | ||
1345 | //! | ||
1346 | //! 1. It acts as a backlog of work that can be done to improve the behavior of the system. | ||
1347 | //! 2. It ensures the code doesn't panic when handling these cases. | ||
1348 | use super::*; | ||
1349 | |||
1350 | #[test] | ||
1351 | fn integers() { | ||
1352 | // We don't currently check integer exhaustiveness. | ||
1353 | check_diagnostics( | ||
1354 | r#" | ||
1355 | fn main() { | ||
1356 | match 5 { | ||
1357 | 10 => (), | ||
1358 | 11..20 => (), | ||
1359 | } | ||
1360 | } | ||
1361 | "#, | ||
1362 | ); | ||
1363 | } | ||
1364 | |||
1365 | #[test] | ||
1366 | fn internal_or() { | ||
1367 | // We do not currently handle patterns with internal `or`s. | ||
1368 | check_diagnostics( | ||
1369 | r#" | ||
1370 | fn main() { | ||
1371 | enum Either { A(bool), B } | ||
1372 | match Either::B { | ||
1373 | Either::A(true | false) => (), | ||
1374 | } | ||
1375 | } | ||
1376 | "#, | ||
1377 | ); | ||
1378 | } | ||
1379 | |||
1380 | #[test] | ||
1381 | fn tuple_of_bools_with_ellipsis_at_end_missing_arm() { | ||
1382 | // We don't currently handle tuple patterns with ellipsis. | ||
1383 | check_diagnostics( | ||
1384 | r#" | ||
1385 | fn main() { | ||
1386 | match (false, true, false) { | ||
1387 | (false, ..) => (), | ||
1388 | } | ||
1389 | } | ||
1390 | "#, | ||
1391 | ); | ||
1392 | } | ||
1393 | |||
1394 | #[test] | ||
1395 | fn tuple_of_bools_with_ellipsis_at_beginning_missing_arm() { | ||
1396 | // We don't currently handle tuple patterns with ellipsis. | ||
1397 | check_diagnostics( | ||
1398 | r#" | ||
1399 | fn main() { | ||
1400 | match (false, true, false) { | ||
1401 | (.., false) => (), | ||
1402 | } | ||
1403 | } | ||
1404 | "#, | ||
1405 | ); | ||
1406 | } | ||
1407 | |||
1408 | #[test] | ||
1409 | fn struct_missing_arm() { | ||
1410 | // We don't currently handle structs. | ||
1411 | check_diagnostics( | ||
1412 | r#" | ||
1413 | struct Foo { a: bool } | ||
1414 | fn main(f: Foo) { | ||
1415 | match f { Foo { a: true } => () } | ||
1416 | } | ||
1417 | "#, | ||
1418 | ); | ||
1419 | } | ||
1420 | } | ||
1421 | } | ||