5 files changed, 48 insertions, 6 deletions

diff --git a/crates/ra_syntax/src/ast.rs b/crates/ra_syntax/src/ast.rs
index 9f5c41b0c..a06a6375d 100644
--- a/crates/ra_syntax/src/ast.rs
+++ b/crates/ra_syntax/src/ast.rs
@@ -17,7 +17,7 @@ pub use self::{
     generated::*,
     traits::*,
     tokens::*,
-    extensions::{PathSegmentKind, StructKind, SelfParamKind},
+    extensions::{PathSegmentKind, StructKind, FieldKind, SelfParamKind},
     expr_extensions::{ElseBranch, PrefixOp, BinOp, LiteralKind},
 };
 
diff --git a/crates/ra_syntax/src/ast/extensions.rs b/crates/ra_syntax/src/ast/extensions.rs
index aec57c380..ca33b43e7 100644
--- a/crates/ra_syntax/src/ast/extensions.rs
+++ b/crates/ra_syntax/src/ast/extensions.rs
@@ -3,11 +3,8 @@
 
 use itertools::Itertools;
 
-use crate::{
-    SmolStr, SyntaxToken,
-    ast::{self, AstNode, children, child_opt},
-    SyntaxKind::*,
-};
+use crate::{SmolStr, SyntaxToken, ast::{self, AstNode, children, child_opt}, SyntaxKind::*, SyntaxElement};
+use ra_parser::SyntaxKind;
 
 impl ast::Name {
     pub fn text(&self) -> &SmolStr {
@@ -217,6 +214,33 @@ impl ast::ExprStmt {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum FieldKind<'a> {
+    Name(&'a ast::NameRef),
+    Index(SyntaxToken<'a>),
+}
+
+impl ast::FieldExpr {
+    pub fn index_token(&self) -> Option<SyntaxToken> {
+        self.syntax
+            .children_with_tokens()
+            // FIXME: Accepting floats here to reject them in validation later
+            .find(|c| c.kind() == SyntaxKind::INT_NUMBER || c.kind() == SyntaxKind::FLOAT_NUMBER)
+            .as_ref()
+            .and_then(SyntaxElement::as_token)
+    }
+
+    pub fn field_access(&self) -> Option<FieldKind> {
+        if let Some(nr) = self.name_ref() {
+            Some(FieldKind::Name(nr))
+        } else if let Some(tok) = self.index_token() {
+            Some(FieldKind::Index(tok))
+        } else {
+            None
+        }
+    }
+}
+
 impl ast::RefPat {
     pub fn is_mut(&self) -> bool {
         self.syntax().children_with_tokens().any(|n| n.kind() == MUT_KW)
diff --git a/crates/ra_syntax/src/syntax_error.rs b/crates/ra_syntax/src/syntax_error.rs
index 4b8c22a57..4198eefdb 100644
--- a/crates/ra_syntax/src/syntax_error.rs
+++ b/crates/ra_syntax/src/syntax_error.rs
@@ -95,6 +95,7 @@ pub enum SyntaxErrorKind {
     InvalidSuffix,
     InvalidBlockAttr,
     InvalidMatchInnerAttr,
+    InvalidTupleIndexFormat,
 }
 
 impl fmt::Display for SyntaxErrorKind {
@@ -139,6 +140,9 @@ impl fmt::Display for SyntaxErrorKind {
             InvalidMatchInnerAttr => {
                 write!(f, "Inner attributes are only allowed directly after the opening brace of the match expression")
             }
+            InvalidTupleIndexFormat => {
+                write!(f, "Tuple (struct) field access is only allowed through decimal integers with no underscores or suffix")
+            }
             ParseError(msg) => write!(f, "{}", msg.0),
         }
     }
diff --git a/crates/ra_syntax/src/validation.rs b/crates/ra_syntax/src/validation.rs
index fc534df83..c2f545173 100644
--- a/crates/ra_syntax/src/validation.rs
+++ b/crates/ra_syntax/src/validation.rs
@@ -3,6 +3,7 @@ mod byte_string;
 mod char;
 mod string;
 mod block;
+mod field_expr;
 
 use crate::{
     SourceFile, SyntaxError, AstNode, SyntaxNode,
@@ -17,6 +18,7 @@ pub(crate) fn validate(file: &SourceFile) -> Vec<SyntaxError> {
         let _ = visitor_ctx(&mut errors)
             .visit::<ast::Literal, _>(validate_literal)
             .visit::<ast::Block, _>(block::validate_block_node)
+            .visit::<ast::FieldExpr, _>(field_expr::validate_field_expr_node)
             .accept(node);
     }
     errors
diff --git a/crates/ra_syntax/src/validation/field_expr.rs b/crates/ra_syntax/src/validation/field_expr.rs
new file mode 100644
index 000000000..2b405062e
--- /dev/null
+++ b/crates/ra_syntax/src/validation/field_expr.rs
@@ -0,0 +1,12 @@
+use crate::{ast::{self, FieldKind},

+            SyntaxError,

+            SyntaxErrorKind::*,

+};

+

+pub(crate) fn validate_field_expr_node(node: &ast::FieldExpr, errors: &mut Vec<SyntaxError>) {

+    if let Some(FieldKind::Index(idx)) = node.field_access() {

+        if idx.text().chars().any(|c| c < '0' || c > '9') {

+            errors.push(SyntaxError::new(InvalidTupleIndexFormat, idx.range()));

+        }

+    }

+}