Initial implementation of or patterns

Author: varkor

src/librustc/cfg/construct.rs

@@ -140,6 +140,11 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
                 self.add_ast_node(pat.hir_id.local_id, &[pats_exit])
             }
 
+            PatKind::Or(ref pats) => {
+                let branches: Vec<_> = pats.iter().map(|p| self.pat(p, pred)).collect();
+                self.add_ast_node(pat.hir_id.local_id, &branches)
+            }
+
             PatKind::Slice(ref pre, ref vec, ref post) => {
                 let pre_exit = self.pats_all(pre.iter(), pred);
                 let vec_exit = self.pats_all(vec.iter(), pre_exit);

src/librustc/hir/intravisit.rs

@@ -709,6 +709,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
                 visitor.visit_pat(&field.pat)
             }
         }
+        PatKind::Or(ref pats) => walk_list!(visitor, visit_pat, pats),
         PatKind::Tuple(ref tuple_elements, _) => {
             walk_list!(visitor, visit_pat, tuple_elements);
         }

src/librustc/hir/lowering.rs

@@ -2669,6 +2669,9 @@ impl<'a> LoweringContext<'a> {
                 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
                 hir::PatKind::TupleStruct(qpath, pats, ddpos)
             }
+            PatKind::Or(ref pats) => {
+                hir::PatKind::Or(pats.iter().map(|x| self.lower_pat(x)).collect())
+            }
             PatKind::Path(ref qself, ref path) => {
                 let qpath = self.lower_qpath(
                     p.id,

src/librustc/hir/mod.rs

@@ -882,6 +882,7 @@ impl Pat {
             PatKind::TupleStruct(_, ref s, _) | PatKind::Tuple(ref s, _) => {
                 s.iter().all(|p| p.walk_(it))
             }
+            PatKind::Or(ref pats) => pats.iter().all(|p| p.walk_(it)),
             PatKind::Box(ref s) | PatKind::Ref(ref s, _) => {
                 s.walk_(it)
             }
@@ -976,6 +977,9 @@ pub enum PatKind {
     /// `0 <= position <= subpats.len()`
     TupleStruct(QPath, HirVec<P<Pat>>, Option<usize>),
 
+    /// An or-pattern `A | B | C`.
+    Or(Vec<P<Pat>>),
+
     /// A path pattern for an unit struct/variant or a (maybe-associated) constant.
     Path(QPath),
 

src/librustc/hir/print.rs

@@ -4,7 +4,7 @@ use syntax::source_map::{SourceMap, Spanned};
 use syntax::parse::ParseSess;
 use syntax::print::pp::{self, Breaks};
 use syntax::print::pp::Breaks::{Consistent, Inconsistent};
-use syntax::print::pprust::{self, Comments, PrintState};
+use syntax::print::pprust::{self, Comments, PrintState, SeparatorSpacing};
 use syntax::symbol::kw;
 use syntax::util::parser::{self, AssocOp, Fixity};
 use syntax_pos::{self, BytePos, FileName};
@@ -1687,6 +1687,10 @@ impl<'a> State<'a> {
                 self.s.space();
                 self.s.word("}");
             }
+            PatKind::Or(ref pats) => {
+                let spacing = SeparatorSpacing::Both;
+                self.strsep("|", spacing, Inconsistent, &pats[..], |s, p| s.print_pat(&p))?;
+            }
             PatKind::Tuple(ref elts, ddpos) => {
                 self.popen();
                 if let Some(ddpos) = ddpos {

src/librustc/middle/mem_categorization.rs

@@ -1290,6 +1290,12 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                 }
             }
 
+            PatKind::Or(ref pats) => {
+                for pat in pats {
+                    self.cat_pattern_(cmt.clone(), &pat, op)?;
+                }
+            }
+
             PatKind::Binding(.., Some(ref subpat)) => {
                 self.cat_pattern_(cmt, &subpat, op)?;
             }

src/librustc_mir/build/matches/mod.rs

@@ -657,6 +657,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     self.visit_bindings(&subpattern.pattern, subpattern_user_ty, f);
                 }
             }
+            PatternKind::Or { ref pats } => {
+                // FIXME(#47184): extract or handle `pattern_user_ty` somehow
+                for pat in pats {
+                    self.visit_bindings(&pat, &pattern_user_ty.clone(), f);
+                }
+            }
         }
     }
 }

src/librustc_mir/build/matches/simplify.rs

@@ -195,6 +195,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 candidate.match_pairs.push(MatchPair::new(place, subpattern));
                 Ok(())
             }
+
+            PatternKind::Or { .. } => {
+                Err(match_pair)
+            }
         }
     }
 }

src/librustc_mir/build/matches/test.rs

@@ -87,6 +87,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             PatternKind::AscribeUserType { .. } |
             PatternKind::Array { .. } |
             PatternKind::Wild |
+            PatternKind::Or { .. } |
             PatternKind::Binding { .. } |
             PatternKind::Leaf { .. } |
             PatternKind::Deref { .. } => {
@@ -130,6 +131,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             PatternKind::Slice { .. } |
             PatternKind::Array { .. } |
             PatternKind::Wild |
+            PatternKind::Or { .. } |
             PatternKind::Binding { .. } |
             PatternKind::AscribeUserType { .. } |
             PatternKind::Leaf { .. } |

src/librustc_mir/hair/pattern/_match.rs

@@ -75,9 +75,6 @@
 ///                     D((r_1, p_(i,2), .., p_(i,n)))
 ///                     D((r_2, p_(i,2), .., p_(i,n)))
 ///
-///     Note that the OR-patterns are not always used directly in Rust, but are used to derive
-///     the exhaustive integer matching rules, so they're written here for posterity.
-///
 /// The algorithm for computing `U`
 /// -------------------------------
 /// The algorithm is inductive (on the number of columns: i.e., components of tuple patterns).
@@ -1359,6 +1356,9 @@ fn pat_constructors<'tcx>(cx: &mut MatchCheckCtxt<'_, 'tcx>,
                 Some(vec![Slice(pat_len)])
             }
         }
+        PatternKind::Or { .. } => {
+            bug!("support for or-patterns has not been fully implemented yet.");
+        }
     }
 }
 
@@ -1884,6 +1884,10 @@ fn specialize<'p, 'a: 'p, 'tcx>(
                     "unexpected ctor {:?} for slice pat", constructor)
             }
         }
+
+        PatternKind::Or { .. } => {
+            bug!("support for or-patterns has not been fully implemented yet.");
+        }
     };
     debug!("specialize({:#?}, {:#?}) = {:#?}", r[0], wild_patterns, head);