From ee822d19b7662a9055bc6693c4c40d8dcf752ea1 Mon Sep 17 00:00:00 2001
From: Josh Mcguigan <joshmcg88@gmail.com>
Date: Sun, 12 Apr 2020 08:40:09 -0700
Subject: handle tuple patterns with ellipsis

---
 crates/ra_hir_def/src/body/lower.rs | 27 ++++++++++++++++++++++-----
 crates/ra_hir_def/src/expr.rs       |  6 +++---
 2 files changed, 25 insertions(+), 8 deletions(-)

(limited to 'crates/ra_hir_def/src')

diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index 6caa87db4..79abe55ce 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -33,6 +33,7 @@ use crate::{
 };
 
 use super::{ExprSource, PatSource};
+use ast::AstChildren;
 
 pub(super) fn lower(
     db: &dyn DefDatabase,
@@ -598,8 +599,8 @@ impl ExprCollector<'_> {
             }
             ast::Pat::TupleStructPat(p) => {
                 let path = p.path().and_then(|path| self.expander.parse_path(path));
-                let args = p.args().map(|p| self.collect_pat(p)).collect();
-                Pat::TupleStruct { path, args }
+                let (args, ellipsis) = self.collect_tuple_pat(p.args());
+                Pat::TupleStruct { path, args, ellipsis }
             }
             ast::Pat::RefPat(p) => {
                 let pat = self.collect_pat_opt(p.pat());
@@ -616,10 +617,10 @@ impl ExprCollector<'_> {
             }
             ast::Pat::ParenPat(p) => return self.collect_pat_opt(p.pat()),
             ast::Pat::TuplePat(p) => {
-                let args = p.args().map(|p| self.collect_pat(p)).collect();
-                Pat::Tuple(args)
+                let (args, ellipsis) = self.collect_tuple_pat(p.args());
+                Pat::Tuple { args, ellipsis }
             }
-            ast::Pat::PlaceholderPat(_) | ast::Pat::DotDotPat(_) => Pat::Wild,
+            ast::Pat::PlaceholderPat(_) => Pat::Wild,
             ast::Pat::RecordPat(p) => {
                 let path = p.path().and_then(|path| self.expander.parse_path(path));
                 let record_field_pat_list =
@@ -665,6 +666,9 @@ impl ExprCollector<'_> {
                     Pat::Missing
                 }
             }
+            ast::Pat::DotDotPat(_) => unreachable!(
+                "`DotDotPat` requires special handling and should not be mapped to a Pat."
+            ),
             // FIXME: implement
             ast::Pat::BoxPat(_) | ast::Pat::RangePat(_) | ast::Pat::MacroPat(_) => Pat::Missing,
         };
@@ -679,6 +683,19 @@ impl ExprCollector<'_> {
             self.missing_pat()
         }
     }
+
+    fn collect_tuple_pat(&mut self, args: AstChildren<ast::Pat>) -> (Vec<PatId>, Option<usize>) {
+        // Find the location of the `..`, if there is one. Note that we do not
+        // consider the possiblity of there being multiple `..` here.
+        let ellipsis = args.clone().position(|p| matches!(p, ast::Pat::DotDotPat(_)));
+        // We want to skip the `..` pattern here, since we account for it above.
+        let args = args
+            .filter(|p| !matches!(p, ast::Pat::DotDotPat(_)))
+            .map(|p| self.collect_pat(p))
+            .collect();
+
+        (args, ellipsis)
+    }
 }
 
 impl From<ast::BinOp> for BinaryOp {
diff --git a/crates/ra_hir_def/src/expr.rs b/crates/ra_hir_def/src/expr.rs
index e11bdf3ec..a0cdad529 100644
--- a/crates/ra_hir_def/src/expr.rs
+++ b/crates/ra_hir_def/src/expr.rs
@@ -374,7 +374,7 @@ pub struct RecordFieldPat {
 pub enum Pat {
     Missing,
     Wild,
-    Tuple(Vec<PatId>),
+    Tuple { args: Vec<PatId>, ellipsis: Option<usize> },
     Or(Vec<PatId>),
     Record { path: Option<Path>, args: Vec<RecordFieldPat>, ellipsis: bool },
     Range { start: ExprId, end: ExprId },
@@ -382,7 +382,7 @@ pub enum Pat {
     Path(Path),
     Lit(ExprId),
     Bind { mode: BindingAnnotation, name: Name, subpat: Option<PatId> },
-    TupleStruct { path: Option<Path>, args: Vec<PatId> },
+    TupleStruct { path: Option<Path>, args: Vec<PatId>, ellipsis: Option<usize> },
     Ref { pat: PatId, mutability: Mutability },
 }
 
@@ -393,7 +393,7 @@ impl Pat {
             Pat::Bind { subpat, .. } => {
                 subpat.iter().copied().for_each(f);
             }
-            Pat::Or(args) | Pat::Tuple(args) | Pat::TupleStruct { args, .. } => {
+            Pat::Or(args) | Pat::Tuple { args, .. } | Pat::TupleStruct { args, .. } => {
                 args.iter().copied().for_each(f);
             }
             Pat::Ref { pat, .. } => f(*pat),
-- 
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