Merge #332

332: Struct types r=matklad a=flodiebold

Infer types for struct fields, and add basic field completions. There's also some code for enums, but I focused on getting structs working.

There's still ways to go before this becomes useful: There's no autoderef (or even reference types) and no inference for `self`, for example.

Co-authored-by: Florian Diebold <[email protected]>

4 files changed, 399 insertions, 46 deletions

diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index f12479fb4..8fb6b6408 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -363,3 +363,73 @@ impl<'a, N: AstNode<'a>> Iterator for AstChildren<'a, N> {
         }
     }
 }
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum StructFlavor<'a> {
+    Tuple(PosFieldList<'a>),
+    Named(NamedFieldDefList<'a>),
+    Unit,
+}
+
+impl<'a> StructFlavor<'a> {
+    fn from_node<N: AstNode<'a>>(node: N) -> StructFlavor<'a> {
+        if let Some(nfdl) = child_opt::<_, NamedFieldDefList>(node) {
+            StructFlavor::Named(nfdl)
+        } else if let Some(pfl) = child_opt::<_, PosFieldList>(node) {
+            StructFlavor::Tuple(pfl)
+        } else {
+            StructFlavor::Unit
+        }
+    }
+}
+
+impl<'a> StructDef<'a> {
+    pub fn flavor(self) -> StructFlavor<'a> {
+        StructFlavor::from_node(self)
+    }
+}
+
+impl<'a> EnumVariant<'a> {
+    pub fn flavor(self) -> StructFlavor<'a> {
+        StructFlavor::from_node(self)
+    }
+}
+
+impl<'a> PointerType<'a> {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+impl<'a> ReferenceType<'a> {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+impl<'a> RefExpr<'a> {
+    pub fn is_mut(&self) -> bool {
+        self.syntax().children().any(|n| n.kind() == MUT_KW)
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum PrefixOp {
+    /// The `*` operator for dereferencing
+    Deref,
+    /// The `!` operator for logical inversion
+    Not,
+    /// The `-` operator for negation
+    Neg,
+}
+
+impl<'a> PrefixExpr<'a> {
+    pub fn op(&self) -> Option<PrefixOp> {
+        match self.syntax().first_child()?.kind() {
+            STAR => Some(PrefixOp::Deref),
+            EXCL => Some(PrefixOp::Not),
+            MINUS => Some(PrefixOp::Neg),
+            _ => None,
+        }
+    }
+}
diff --git a/crates/ra_syntax/src/ast/generated.rs b/crates/ra_syntax/src/ast/generated.rs
index c73533861..c22e026cf 100644
--- a/crates/ra_syntax/src/ast/generated.rs
+++ b/crates/ra_syntax/src/ast/generated.rs
@@ -131,7 +131,15 @@ impl<R: TreeRoot<RaTypes>> ArrayTypeNode<R> {
 }
 
 
-impl<'a> ArrayType<'a> {}
+impl<'a> ArrayType<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+
+    pub fn expr(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // Attr
 #[derive(Debug, Clone, Copy,)]
@@ -806,7 +814,94 @@ impl<'a> ast::NameOwner<'a> for EnumDef<'a> {}
 impl<'a> ast::TypeParamsOwner<'a> for EnumDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for EnumDef<'a> {}
 impl<'a> ast::DocCommentsOwner<'a> for EnumDef<'a> {}
-impl<'a> EnumDef<'a> {}
+impl<'a> EnumDef<'a> {
+    pub fn variant_list(self) -> Option<EnumVariantList<'a>> {
+        super::child_opt(self)
+    }
+}
+
+// EnumVariant
+#[derive(Debug, Clone, Copy,)]
+pub struct EnumVariantNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type EnumVariant<'a> = EnumVariantNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<EnumVariantNode<R1>> for EnumVariantNode<R2> {
+    fn eq(&self, other: &EnumVariantNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for EnumVariantNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for EnumVariantNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for EnumVariant<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            ENUM_VARIANT => Some(EnumVariant { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> EnumVariantNode<R> {
+    pub fn borrowed(&self) -> EnumVariant {
+        EnumVariantNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> EnumVariantNode {
+        EnumVariantNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> ast::NameOwner<'a> for EnumVariant<'a> {}
+impl<'a> EnumVariant<'a> {
+    pub fn expr(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
+}
+
+// EnumVariantList
+#[derive(Debug, Clone, Copy,)]
+pub struct EnumVariantListNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type EnumVariantList<'a> = EnumVariantListNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<EnumVariantListNode<R1>> for EnumVariantListNode<R2> {
+    fn eq(&self, other: &EnumVariantListNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for EnumVariantListNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for EnumVariantListNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for EnumVariantList<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            ENUM_VARIANT_LIST => Some(EnumVariantList { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> EnumVariantListNode<R> {
+    pub fn borrowed(&self) -> EnumVariantList {
+        EnumVariantListNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> EnumVariantListNode {
+        EnumVariantListNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> EnumVariantList<'a> {
+    pub fn variants(self) -> impl Iterator<Item = EnumVariant<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // Expr
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -1036,7 +1131,15 @@ impl<R: TreeRoot<RaTypes>> FieldExprNode<R> {
 }
 
 
-impl<'a> FieldExpr<'a> {}
+impl<'a> FieldExpr<'a> {
+    pub fn expr(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
+
+    pub fn name_ref(self) -> Option<NameRef<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // FieldPatList
 #[derive(Debug, Clone, Copy,)]
@@ -1163,7 +1266,15 @@ impl<R: TreeRoot<RaTypes>> FnPointerTypeNode<R> {
 }
 
 
-impl<'a> FnPointerType<'a> {}
+impl<'a> FnPointerType<'a> {
+    pub fn param_list(self) -> Option<ParamList<'a>> {
+        super::child_opt(self)
+    }
+
+    pub fn ret_type(self) -> Option<RetType<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // ForExpr
 #[derive(Debug, Clone, Copy,)]
@@ -1246,7 +1357,11 @@ impl<R: TreeRoot<RaTypes>> ForTypeNode<R> {
 }
 
 
-impl<'a> ForType<'a> {}
+impl<'a> ForType<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // IfExpr
 #[derive(Debug, Clone, Copy,)]
@@ -1935,6 +2050,10 @@ impl<'a> MethodCallExpr<'a> {
     pub fn expr(self) -> Option<Expr<'a>> {
         super::child_opt(self)
     }
+
+    pub fn name_ref(self) -> Option<NameRef<'a>> {
+        super::child_opt(self)
+    }
 }
 
 // Module
@@ -2142,7 +2261,15 @@ impl<R: TreeRoot<RaTypes>> NamedFieldNode<R> {
 }
 
 
-impl<'a> NamedField<'a> {}
+impl<'a> NamedField<'a> {
+    pub fn name_ref(self) -> Option<NameRef<'a>> {
+        super::child_opt(self)
+    }
+
+    pub fn expr(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // NamedFieldDef
 #[derive(Debug, Clone, Copy,)]
@@ -2181,7 +2308,52 @@ impl<R: TreeRoot<RaTypes>> NamedFieldDefNode<R> {
 
 impl<'a> ast::NameOwner<'a> for NamedFieldDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for NamedFieldDef<'a> {}
-impl<'a> NamedFieldDef<'a> {}
+impl<'a> NamedFieldDef<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
+
+// NamedFieldDefList
+#[derive(Debug, Clone, Copy,)]
+pub struct NamedFieldDefListNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type NamedFieldDefList<'a> = NamedFieldDefListNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<NamedFieldDefListNode<R1>> for NamedFieldDefListNode<R2> {
+    fn eq(&self, other: &NamedFieldDefListNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for NamedFieldDefListNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for NamedFieldDefListNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for NamedFieldDefList<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            NAMED_FIELD_DEF_LIST => Some(NamedFieldDefList { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> NamedFieldDefListNode<R> {
+    pub fn borrowed(&self) -> NamedFieldDefList {
+        NamedFieldDefListNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> NamedFieldDefListNode {
+        NamedFieldDefListNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> NamedFieldDefList<'a> {
+    pub fn fields(self) -> impl Iterator<Item = NamedFieldDef<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // NamedFieldList
 #[derive(Debug, Clone, Copy,)]
@@ -2218,7 +2390,11 @@ impl<R: TreeRoot<RaTypes>> NamedFieldListNode<R> {
 }
 
 
-impl<'a> NamedFieldList<'a> {}
+impl<'a> NamedFieldList<'a> {
+    pub fn fields(self) -> impl Iterator<Item = NamedField<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // NeverType
 #[derive(Debug, Clone, Copy,)]
@@ -2451,7 +2627,11 @@ impl<R: TreeRoot<RaTypes>> ParenTypeNode<R> {
 }
 
 
-impl<'a> ParenType<'a> {}
+impl<'a> ParenType<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // Pat
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -2816,7 +2996,94 @@ impl<R: TreeRoot<RaTypes>> PointerTypeNode<R> {
 }
 
 
-impl<'a> PointerType<'a> {}
+impl<'a> PointerType<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
+
+// PosField
+#[derive(Debug, Clone, Copy,)]
+pub struct PosFieldNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type PosField<'a> = PosFieldNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<PosFieldNode<R1>> for PosFieldNode<R2> {
+    fn eq(&self, other: &PosFieldNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for PosFieldNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for PosFieldNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for PosField<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            POS_FIELD => Some(PosField { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> PosFieldNode<R> {
+    pub fn borrowed(&self) -> PosField {
+        PosFieldNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> PosFieldNode {
+        PosFieldNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> ast::AttrsOwner<'a> for PosField<'a> {}
+impl<'a> PosField<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
+
+// PosFieldList
+#[derive(Debug, Clone, Copy,)]
+pub struct PosFieldListNode<R: TreeRoot<RaTypes> = OwnedRoot> {
+    pub(crate) syntax: SyntaxNode<R>,
+}
+pub type PosFieldList<'a> = PosFieldListNode<RefRoot<'a>>;
+
+impl<R1: TreeRoot<RaTypes>, R2: TreeRoot<RaTypes>> PartialEq<PosFieldListNode<R1>> for PosFieldListNode<R2> {
+    fn eq(&self, other: &PosFieldListNode<R1>) -> bool { self.syntax == other.syntax }
+}
+impl<R: TreeRoot<RaTypes>> Eq for PosFieldListNode<R> {}
+impl<R: TreeRoot<RaTypes>> Hash for PosFieldListNode<R> {
+    fn hash<H: Hasher>(&self, state: &mut H) { self.syntax.hash(state) }
+}
+
+impl<'a> AstNode<'a> for PosFieldList<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            POS_FIELD_LIST => Some(PosFieldList { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<R: TreeRoot<RaTypes>> PosFieldListNode<R> {
+    pub fn borrowed(&self) -> PosFieldList {
+        PosFieldListNode { syntax: self.syntax.borrowed() }
+    }
+    pub fn owned(&self) -> PosFieldListNode {
+        PosFieldListNode { syntax: self.syntax.owned() }
+    }
+}
+
+
+impl<'a> PosFieldList<'a> {
+    pub fn fields(self) -> impl Iterator<Item = PosField<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // PrefixExpr
 #[derive(Debug, Clone, Copy,)]
@@ -3046,7 +3313,11 @@ impl<R: TreeRoot<RaTypes>> ReferenceTypeNode<R> {
 }
 
 
-impl<'a> ReferenceType<'a> {}
+impl<'a> ReferenceType<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // RetType
 #[derive(Debug, Clone, Copy,)]
@@ -3239,7 +3510,11 @@ impl<R: TreeRoot<RaTypes>> SliceTypeNode<R> {
 }
 
 
-impl<'a> SliceType<'a> {}
+impl<'a> SliceType<'a> {
+    pub fn type_ref(self) -> Option<TypeRef<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // SourceFile
 #[derive(Debug, Clone, Copy,)]
@@ -3426,11 +3701,7 @@ impl<'a> ast::NameOwner<'a> for StructDef<'a> {}
 impl<'a> ast::TypeParamsOwner<'a> for StructDef<'a> {}
 impl<'a> ast::AttrsOwner<'a> for StructDef<'a> {}
 impl<'a> ast::DocCommentsOwner<'a> for StructDef<'a> {}
-impl<'a> StructDef<'a> {
-    pub fn fields(self) -> impl Iterator<Item = NamedFieldDef<'a>> + 'a {
-        super::children(self)
-    }
-}
+impl<'a> StructDef<'a> {}
 
 // StructLit
 #[derive(Debug, Clone, Copy,)]
@@ -3467,7 +3738,15 @@ impl<R: TreeRoot<RaTypes>> StructLitNode<R> {
 }
 
 
-impl<'a> StructLit<'a> {}
+impl<'a> StructLit<'a> {
+    pub fn path(self) -> Option<Path<'a>> {
+        super::child_opt(self)
+    }
+
+    pub fn named_field_list(self) -> Option<NamedFieldList<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // StructPat
 #[derive(Debug, Clone, Copy,)]
@@ -3770,7 +4049,11 @@ impl<R: TreeRoot<RaTypes>> TupleTypeNode<R> {
 }
 
 
-impl<'a> TupleType<'a> {}
+impl<'a> TupleType<'a> {
+    pub fn fields(self) -> impl Iterator<Item = TypeRef<'a>> + 'a {
+        super::children(self)
+    }
+}
 
 // TypeDef
 #[derive(Debug, Clone, Copy,)]
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index e3b9032a0..4bcff4e14 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -261,18 +261,20 @@ Grammar(
                 "TypeParamsOwner",
                 "AttrsOwner",
                 "DocCommentsOwner"
-            ],
-            collections: [
-                ["fields", "NamedFieldDef"]
             ]
         ),
-        "NamedFieldDef": ( traits: ["NameOwner", "AttrsOwner"] ),
+        "NamedFieldDefList": (collections: [["fields", "NamedFieldDef"]]),
+        "NamedFieldDef": ( traits: ["NameOwner", "AttrsOwner"], options: ["TypeRef"] ),
+        "PosFieldList": (collections: [["fields", "PosField"]]),
+        "PosField": ( traits: ["AttrsOwner"], options: ["TypeRef"]),
         "EnumDef": ( traits: [
             "NameOwner",
             "TypeParamsOwner",
             "AttrsOwner",
             "DocCommentsOwner"
-        ] ),
+        ], options: [["variant_list", "EnumVariantList"]] ),
+        "EnumVariantList": ( collections: [["variants", "EnumVariant"]] ),
+        "EnumVariant": ( traits: ["NameOwner"], options: ["Expr"] ),
         "TraitDef": ( traits: ["NameOwner", "AttrsOwner", "DocCommentsOwner"] ),
         "Module": (
             traits: ["NameOwner", "AttrsOwner", "DocCommentsOwner" ],
@@ -301,17 +303,17 @@ Grammar(
         ] ),
         "ImplItem": (),
 
-        "ParenType": (),
-        "TupleType": (),
+        "ParenType": (options: ["TypeRef"]),
+        "TupleType": ( collections: [["fields", "TypeRef"]] ),
         "NeverType": (),
         "PathType": (options: ["Path"]),
-        "PointerType": (),
-        "ArrayType": (),
-        "SliceType": (),
-        "ReferenceType": (),
+        "PointerType": (options: ["TypeRef"]),
+        "ArrayType": ( options: ["TypeRef", "Expr"] ),
+        "SliceType": ( options: ["TypeRef"] ),
+        "ReferenceType": (options: ["TypeRef"]),
         "PlaceholderType": (),
-        "FnPointerType": (),
-        "ForType": (),
+        "FnPointerType": (options: ["ParamList", "RetType"]),
+        "ForType": (options: ["TypeRef"]),
         "ImplTraitType": (),
         "DynTraitType": (),
 
@@ -392,19 +394,19 @@ Grammar(
             collections: [ [ "pats", "Pat" ] ]
         ),
         "MatchGuard": (),
-        "StructLit": (),
-        "NamedFieldList": (),
-        "NamedField": (),
+        "StructLit": (options: ["Path", "NamedFieldList"]),
+        "NamedFieldList": (collections: [ ["fields", "NamedField"] ]),
+        "NamedField": (options: ["NameRef", "Expr"]),
         "CallExpr": (
             traits: ["ArgListOwner"],
             options: [ "Expr" ],
         ),
         "MethodCallExpr": (
             traits: ["ArgListOwner"],
-            options: [ "Expr" ],
+            options: [ "Expr", "NameRef" ],
         ),
         "IndexExpr": (),
-        "FieldExpr": (),
+        "FieldExpr": (options: ["Expr", "NameRef"]),
         "TryExpr": (options: ["Expr"]),
         "CastExpr": (options: ["Expr", "TypeRef"]),
         "RefExpr": (options: ["Expr"]),
diff --git a/crates/ra_syntax/src/grammar/expressions.rs b/crates/ra_syntax/src/grammar/expressions.rs
index da78d85a2..2d1f17491 100644
--- a/crates/ra_syntax/src/grammar/expressions.rs
+++ b/crates/ra_syntax/src/grammar/expressions.rs
@@ -283,14 +283,10 @@ fn postfix_expr(
             // }
             L_PAREN if allow_calls => call_expr(p, lhs),
             L_BRACK if allow_calls => index_expr(p, lhs),
-            DOT if p.nth(1) == IDENT => {
-                if p.nth(2) == L_PAREN || p.nth(2) == COLONCOLON {
-                    method_call_expr(p, lhs)
-                } else {
-                    field_expr(p, lhs)
-                }
+            DOT if p.nth(1) == IDENT && (p.nth(2) == L_PAREN || p.nth(2) == COLONCOLON) => {
+                method_call_expr(p, lhs)
             }
-            DOT if p.nth(1) == INT_NUMBER => field_expr(p, lhs),
+            DOT => field_expr(p, lhs),
             // test postfix_range
             // fn foo() { let x = 1..; }
             DOTDOT | DOTDOTEQ if !EXPR_FIRST.contains(p.nth(1)) => {
@@ -355,13 +351,15 @@ fn method_call_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
 //     x.0.bar;
 // }
 fn field_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
-    assert!(p.at(DOT) && (p.nth(1) == IDENT || p.nth(1) == INT_NUMBER));
+    assert!(p.at(DOT));
     let m = lhs.precede(p);
     p.bump();
     if p.at(IDENT) {
         name_ref(p)
-    } else {
+    } else if p.at(INT_NUMBER) {
         p.bump()
+    } else {
+        p.error("expected field name or number")
     }
     m.complete(p, FIELD_EXPR)
 }