libnixf: report error if extra token is consumed (#506)

Fixes: #483

libnixf/src/Parse/ParseSupport.cpp

@@ -3,6 +3,7 @@
 
 #include "Parser.h"
 
+#include "nixf/Basic/TokenKinds.h"
 #include "nixf/Parse/Parser.h"
 
 using namespace nixf;
@@ -39,6 +40,16 @@ std::shared_ptr<Node> nixf::parse(std::string_view Src,
   return P.parse();
 }
 
+std::shared_ptr<Expr> nixf::Parser::parse() {
+  auto Expr = parseExpr();
+  if (Token Tok = peek(); Tok.kind() != tok::tok_eof) {
+    // TODO: maybe we'd like to have multiple expressions in a single file.
+    // Report an error.
+    Diags.emplace_back(Diagnostic::DK_UnexpectedText, Tok.range());
+  }
+  return Expr;
+}
+
 void Parser::resetLookAheadBuf() {
   if (!LookAheadBuf.empty()) {
     Token Tok = LookAheadBuf.front();

libnixf/src/Parse/Parser.h

@@ -334,7 +334,8 @@ class Parser {
   /// \endcode
   std::shared_ptr<ExprWith> parseExprWith();
 
-  std::shared_ptr<Expr> parse() { return parseExpr(); }
+  /// Top-level parsing.
+  std::shared_ptr<Expr> parse();
 };
 
 } // namespace nixf

libnixf/test/Parse/ParseExpr.cpp

@@ -7,6 +7,18 @@ namespace {
 using namespace nixf;
 using namespace std::string_view_literals;
 
+TEST(Parser, ParseEnd) {
+  auto Src = R"({a = 1;},)"sv;
+
+  std::vector<Diagnostic> Diags;
+  Parser P(Src, Diags);
+
+  P.parse();
+
+  // See that we have diagnostic at the last token ","
+  ASSERT_EQ(Diags.size(), 1);
+}
+
 TEST(Parser, SelectOK) {
   auto Src = R"(a.b.c)"sv;