5 files changed, 422 insertions, 16 deletions

diff --git a/crates/libsyntax2/src/algo/visit.rs b/crates/libsyntax2/src/algo/visit.rs
index a36c8f45e..9f1c127c7 100644
--- a/crates/libsyntax2/src/algo/visit.rs
+++ b/crates/libsyntax2/src/algo/visit.rs
@@ -6,6 +6,10 @@ pub fn visitor<'a, T>() -> impl Visitor<'a, Output=T> {
     EmptyVisitor { ph: PhantomData }
 }
 
+pub fn visitor_ctx<'a, T, C>(ctx: C) -> impl VisitorCtx<'a, Output=T, Ctx=C> {
+    EmptyVisitorCtx { ph: PhantomData, ctx }
+}
+
 pub trait Visitor<'a>: Sized {
     type Output;
     fn accept(self, node: SyntaxNodeRef<'a>) -> Option<Self::Output>;
@@ -17,6 +21,18 @@ pub trait Visitor<'a>: Sized {
     }
 }
 
+pub trait VisitorCtx<'a>: Sized {
+    type Output;
+    type Ctx;
+    fn accept(self, node: SyntaxNodeRef<'a>) -> Result<Self::Output, Self::Ctx>;
+    fn visit<N, F>(self, f: F) -> VisCtx<Self, N, F>
+        where N: AstNode<'a>,
+              F: FnOnce(N, Self::Ctx) -> Self::Output,
+    {
+        VisCtx { inner: self, f, ph: PhantomData }
+    }
+}
+
 #[derive(Debug)]
 struct EmptyVisitor<T> {
     ph: PhantomData<fn() -> T>
@@ -31,6 +47,21 @@ impl<'a, T> Visitor<'a> for EmptyVisitor<T> {
 }
 
 #[derive(Debug)]
+struct EmptyVisitorCtx<T, C> {
+    ctx: C,
+    ph: PhantomData<fn() -> T>,
+}
+
+impl<'a, T, C> VisitorCtx<'a> for EmptyVisitorCtx<T, C> {
+    type Output = T;
+    type Ctx = C;
+
+    fn accept(self, _node: SyntaxNodeRef<'a>) -> Result<T, C> {
+        Err(self.ctx)
+    }
+}
+
+#[derive(Debug)]
 pub struct Vis<V, N, F> {
     inner: V,
     f: F,
@@ -50,3 +81,30 @@ impl<'a, V, N, F> Visitor<'a> for Vis<V, N, F>
         inner.accept(node).or_else(|| N::cast(node).map(f))
     }
 }
+
+#[derive(Debug)]
+pub struct VisCtx<V, N, F> {
+    inner: V,
+    f: F,
+    ph: PhantomData<fn(N)>,
+}
+
+impl<'a, V, N, F> VisitorCtx<'a> for VisCtx<V, N, F>
+    where
+        V: VisitorCtx<'a>,
+        N: AstNode<'a>,
+        F: FnOnce(N, <V as VisitorCtx<'a>>::Ctx) -> <V as VisitorCtx<'a>>::Output,
+{
+    type Output = <V as VisitorCtx<'a>>::Output;
+    type Ctx = <V as VisitorCtx<'a>>::Ctx;
+
+    fn accept(self, node: SyntaxNodeRef<'a>) -> Result<Self::Output, Self::Ctx> {
+        let VisCtx { inner, f, .. } = self;
+        inner.accept(node).or_else(|ctx|
+            match N::cast(node) {
+                None => Err(ctx),
+                Some(node) => Ok(f(node, ctx))
+            }
+        )
+    }
+}
diff --git a/crates/libsyntax2/src/algo/walk.rs b/crates/libsyntax2/src/algo/walk.rs
index d8797c453..536ee705f 100644
--- a/crates/libsyntax2/src/algo/walk.rs
+++ b/crates/libsyntax2/src/algo/walk.rs
@@ -17,19 +17,19 @@ pub enum WalkEvent<'a> {
 }
 
 pub fn walk<'a>(root: SyntaxNodeRef<'a>) -> impl Iterator<Item = WalkEvent<'a>> {
-    generate(Some(WalkEvent::Enter(root)), |pos| {
+    generate(Some(WalkEvent::Enter(root)), move |pos| {
         let next = match *pos {
             WalkEvent::Enter(node) => match node.first_child() {
                 Some(child) => WalkEvent::Enter(child),
                 None => WalkEvent::Exit(node),
             },
             WalkEvent::Exit(node) => {
+                if node == root {
+                    return None;
+                }
                 match node.next_sibling() {
                     Some(sibling) => WalkEvent::Enter(sibling),
-                    None => match node.parent() {
-                        Some(node) => WalkEvent::Exit(node),
-                        None => return None,
-                    },
+                    None => WalkEvent::Exit(node.parent().unwrap()),
                 }
             }
         };
diff --git a/crates/libsyntax2/src/ast/generated.rs b/crates/libsyntax2/src/ast/generated.rs
index 7d746a85b..6926c0535 100644
--- a/crates/libsyntax2/src/ast/generated.rs
+++ b/crates/libsyntax2/src/ast/generated.rs
@@ -80,6 +80,25 @@ impl<'a> AstNode<'a> for BinExpr<'a> {
 
 impl<'a> BinExpr<'a> {}
 
+// BindPat
+#[derive(Debug, Clone, Copy)]
+pub struct BindPat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for BindPat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            BIND_PAT => Some(BindPat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> ast::NameOwner<'a> for BindPat<'a> {}
+impl<'a> BindPat<'a> {}
+
 // Block
 #[derive(Debug, Clone, Copy)]
 pub struct Block<'a> {
@@ -96,7 +115,11 @@ impl<'a> AstNode<'a> for Block<'a> {
     fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
 }
 
-impl<'a> Block<'a> {}
+impl<'a> Block<'a> {
+    pub fn let_stmts(self) -> impl Iterator<Item = LetStmt<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // BlockExpr
 #[derive(Debug, Clone, Copy)]
@@ -378,6 +401,24 @@ impl<'a> AstNode<'a> for FieldExpr<'a> {
 
 impl<'a> FieldExpr<'a> {}
 
+// FieldPatList
+#[derive(Debug, Clone, Copy)]
+pub struct FieldPatList<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for FieldPatList<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            FIELD_PAT_LIST => Some(FieldPatList { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> FieldPatList<'a> {}
+
 // FnDef
 #[derive(Debug, Clone, Copy)]
 pub struct FnDef<'a> {
@@ -397,7 +438,11 @@ impl<'a> AstNode<'a> for FnDef<'a> {
 impl<'a> ast::NameOwner<'a> for FnDef<'a> {}
 impl<'a> ast::TypeParamsOwner<'a> for FnDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for FnDef<'a> {}
-impl<'a> FnDef<'a> {}
+impl<'a> FnDef<'a> {
+    pub fn param_list(self) -> Option<ParamList<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // FnPointerType
 #[derive(Debug, Clone, Copy)]
@@ -561,6 +606,28 @@ impl<'a> AstNode<'a> for LambdaExpr<'a> {
 
 impl<'a> LambdaExpr<'a> {}
 
+// LetStmt
+#[derive(Debug, Clone, Copy)]
+pub struct LetStmt<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for LetStmt<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            LET_STMT => Some(LetStmt { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> LetStmt<'a> {
+    pub fn pat(self) -> Option<Pat<'a>> {
+        super::child_opt(self)
+    }
+}
+
 // LoopExpr
 #[derive(Debug, Clone, Copy)]
 pub struct LoopExpr<'a> {
@@ -831,6 +898,50 @@ impl<'a> ast::TypeParamsOwner<'a> for NominalDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for NominalDef<'a> {}
 impl<'a> NominalDef<'a> {}
 
+// Param
+#[derive(Debug, Clone, Copy)]
+pub struct Param<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for Param<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            PARAM => Some(Param { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> Param<'a> {
+    pub fn pat(self) -> Option<Pat<'a>> {
+        super::child_opt(self)
+    }
+}
+
+// ParamList
+#[derive(Debug, Clone, Copy)]
+pub struct ParamList<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for ParamList<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            PARAM_LIST => Some(ParamList { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> ParamList<'a> {
+    pub fn params(self) -> impl Iterator<Item = Param<'a>> + 'a {
+        super::children(self)
+    }
+}
+
 // ParenExpr
 #[derive(Debug, Clone, Copy)]
 pub struct ParenExpr<'a> {
@@ -867,6 +978,55 @@ impl<'a> AstNode<'a> for ParenType<'a> {
 
 impl<'a> ParenType<'a> {}
 
+// Pat
+#[derive(Debug, Clone, Copy)]
+pub enum Pat<'a> {
+    RefPat(RefPat<'a>),
+    BindPat(BindPat<'a>),
+    PlaceholderPat(PlaceholderPat<'a>),
+    PathPat(PathPat<'a>),
+    StructPat(StructPat<'a>),
+    FieldPatList(FieldPatList<'a>),
+    TupleStructPat(TupleStructPat<'a>),
+    TuplePat(TuplePat<'a>),
+    SlicePat(SlicePat<'a>),
+    RangePat(RangePat<'a>),
+}
+
+impl<'a> AstNode<'a> for Pat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            REF_PAT => Some(Pat::RefPat(RefPat { syntax })),
+            BIND_PAT => Some(Pat::BindPat(BindPat { syntax })),
+            PLACEHOLDER_PAT => Some(Pat::PlaceholderPat(PlaceholderPat { syntax })),
+            PATH_PAT => Some(Pat::PathPat(PathPat { syntax })),
+            STRUCT_PAT => Some(Pat::StructPat(StructPat { syntax })),
+            FIELD_PAT_LIST => Some(Pat::FieldPatList(FieldPatList { syntax })),
+            TUPLE_STRUCT_PAT => Some(Pat::TupleStructPat(TupleStructPat { syntax })),
+            TUPLE_PAT => Some(Pat::TuplePat(TuplePat { syntax })),
+            SLICE_PAT => Some(Pat::SlicePat(SlicePat { syntax })),
+            RANGE_PAT => Some(Pat::RangePat(RangePat { syntax })),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> {
+        match self {
+            Pat::RefPat(inner) => inner.syntax(),
+            Pat::BindPat(inner) => inner.syntax(),
+            Pat::PlaceholderPat(inner) => inner.syntax(),
+            Pat::PathPat(inner) => inner.syntax(),
+            Pat::StructPat(inner) => inner.syntax(),
+            Pat::FieldPatList(inner) => inner.syntax(),
+            Pat::TupleStructPat(inner) => inner.syntax(),
+            Pat::TuplePat(inner) => inner.syntax(),
+            Pat::SlicePat(inner) => inner.syntax(),
+            Pat::RangePat(inner) => inner.syntax(),
+        }
+    }
+}
+
+impl<'a> Pat<'a> {}
+
 // PathExpr
 #[derive(Debug, Clone, Copy)]
 pub struct PathExpr<'a> {
@@ -885,6 +1045,24 @@ impl<'a> AstNode<'a> for PathExpr<'a> {
 
 impl<'a> PathExpr<'a> {}
 
+// PathPat
+#[derive(Debug, Clone, Copy)]
+pub struct PathPat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for PathPat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            PATH_PAT => Some(PathPat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> PathPat<'a> {}
+
 // PathType
 #[derive(Debug, Clone, Copy)]
 pub struct PathType<'a> {
@@ -903,6 +1081,24 @@ impl<'a> AstNode<'a> for PathType<'a> {
 
 impl<'a> PathType<'a> {}
 
+// PlaceholderPat
+#[derive(Debug, Clone, Copy)]
+pub struct PlaceholderPat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for PlaceholderPat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            PLACEHOLDER_PAT => Some(PlaceholderPat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> PlaceholderPat<'a> {}
+
 // PlaceholderType
 #[derive(Debug, Clone, Copy)]
 pub struct PlaceholderType<'a> {
@@ -975,6 +1171,24 @@ impl<'a> AstNode<'a> for RangeExpr<'a> {
 
 impl<'a> RangeExpr<'a> {}
 
+// RangePat
+#[derive(Debug, Clone, Copy)]
+pub struct RangePat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for RangePat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            RANGE_PAT => Some(RangePat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> RangePat<'a> {}
+
 // RefExpr
 #[derive(Debug, Clone, Copy)]
 pub struct RefExpr<'a> {
@@ -993,6 +1207,24 @@ impl<'a> AstNode<'a> for RefExpr<'a> {
 
 impl<'a> RefExpr<'a> {}
 
+// RefPat
+#[derive(Debug, Clone, Copy)]
+pub struct RefPat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for RefPat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            REF_PAT => Some(RefPat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> RefPat<'a> {}
+
 // ReferenceType
 #[derive(Debug, Clone, Copy)]
 pub struct ReferenceType<'a> {
@@ -1055,6 +1287,24 @@ impl<'a> Root<'a> {
     }
 }
 
+// SlicePat
+#[derive(Debug, Clone, Copy)]
+pub struct SlicePat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for SlicePat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            SLICE_PAT => Some(SlicePat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> SlicePat<'a> {}
+
 // SliceType
 #[derive(Debug, Clone, Copy)]
 pub struct SliceType<'a> {
@@ -1137,6 +1387,24 @@ impl<'a> AstNode<'a> for StructLit<'a> {
 
 impl<'a> StructLit<'a> {}
 
+// StructPat
+#[derive(Debug, Clone, Copy)]
+pub struct StructPat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for StructPat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            STRUCT_PAT => Some(StructPat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> StructPat<'a> {}
+
 // TokenTree
 #[derive(Debug, Clone, Copy)]
 pub struct TokenTree<'a> {
@@ -1211,6 +1479,42 @@ impl<'a> AstNode<'a> for TupleExpr<'a> {
 
 impl<'a> TupleExpr<'a> {}
 
+// TuplePat
+#[derive(Debug, Clone, Copy)]
+pub struct TuplePat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for TuplePat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            TUPLE_PAT => Some(TuplePat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> TuplePat<'a> {}
+
+// TupleStructPat
+#[derive(Debug, Clone, Copy)]
+pub struct TupleStructPat<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for TupleStructPat<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            TUPLE_STRUCT_PAT => Some(TupleStructPat { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> TupleStructPat<'a> {}
+
 // TupleType
 #[derive(Debug, Clone, Copy)]
 pub struct TupleType<'a> {
diff --git a/crates/libsyntax2/src/grammar.ron b/crates/libsyntax2/src/grammar.ron
index a753d5e48..3a125ace6 100644
--- a/crates/libsyntax2/src/grammar.ron
+++ b/crates/libsyntax2/src/grammar.ron
@@ -241,11 +241,16 @@ Grammar(
                 ["modules", "Module"],
             ]
         ),
-        "FnDef": ( traits: [
-            "NameOwner",
-            "TypeParamsOwner",
-            "AttrsOwner",
-        ] ),
+        "FnDef": (
+            traits: [
+                "NameOwner",
+                "TypeParamsOwner",
+                "AttrsOwner",
+            ],
+            options: [
+                ["param_list", "ParamList"]
+            ],
+        ),
         "StructDef": (
             traits: [
                 "NameOwner",
@@ -393,13 +398,52 @@ Grammar(
             ],
         ),
 
+        "RefPat": (),
+        "BindPat": ( traits: ["NameOwner"] ),
+        "PlaceholderPat": (),
+        "PathPat": (),
+        "StructPat": (),
+        "FieldPatList": (),
+        "TupleStructPat": (),
+        "TuplePat": (),
+        "SlicePat": (),
+        "RangePat": (),
+
+        "Pat": (
+            enum: [
+                "RefPat",
+                "BindPat",
+                "PlaceholderPat",
+                "PathPat",
+                "StructPat",
+                "FieldPatList",
+                "TupleStructPat",
+                "TuplePat",
+                "SlicePat",
+                "RangePat",
+            ],
+        ),
+
         "Name": (),
         "NameRef": (),
         "Attr": ( options: [ ["value", "TokenTree"] ] ),
         "TokenTree": (),
         "TypeParamList": ( collections: [ ["type_params", "TypeParam" ] ]),
-        "TypeParam": ( traits: ["NameOwner"]),
+        "TypeParam": ( traits: ["NameOwner"] ),
         "WhereClause": (),
-        "Block": (),
+        "LetStmt": ( options: [ ["pat", "Pat"] ]),
+        "Block": (
+            collections: [
+                ["let_stmts", "LetStmt"],
+            ]
+        ),
+        "ParamList": (
+            collections: [
+                ["params", "Param"]
+            ]
+        ),
+        "Param": (
+            options: [["pat", "Pat"]],
+        )
     },
 )
diff --git a/crates/libsyntax2/src/grammar/items/mod.rs b/crates/libsyntax2/src/grammar/items/mod.rs
index a285892df..7c6f7b63e 100644
--- a/crates/libsyntax2/src/grammar/items/mod.rs
+++ b/crates/libsyntax2/src/grammar/items/mod.rs
@@ -115,7 +115,7 @@ pub(super) fn maybe_item(p: &mut Parser, flavor: ItemFlavor) -> MaybeItem {
         // test unsafe_fn
         // unsafe fn foo() {}
         FN_KW => {
-            function(p, flavor);
+            fn_def(p, flavor);
             FN_DEF
         }
 
@@ -227,7 +227,7 @@ fn extern_item_list(p: &mut Parser) {
     m.complete(p, EXTERN_ITEM_LIST);
 }
 
-fn function(p: &mut Parser, flavor: ItemFlavor) {
+fn fn_def(p: &mut Parser, flavor: ItemFlavor) {
     assert!(p.at(FN_KW));
     p.bump();