Add helpers for matching common subtrees in parse tests.

parser/parse_test_helpers.h

@@ -316,6 +316,26 @@ auto MatchNode(Args... args) -> ExpectedNode {
     return MatchNode(ParseNodeKind::kind(), args...); \
   }
 #include "parse_node_kind.def"
+
+// Helper for matching a designator `lhs.rhs`.
+auto MatchDesignator(ExpectedNode lhs, std::string rhs) -> ExpectedNode {
+  return MatchDesignatorExpression(lhs, MatchDesignatedName(rhs));
+}
+
+// Helper for matching a function parameter list.
+template <typename... Args>
+auto MatchParameters(Args... args) -> ExpectedNode {
+  return MatchParameterList("(", args..., MatchParameterListEnd());
+}
+
+// Helper for matching the statements in the body of a simple function
+// definition with no parameters.
+template <typename... Args>
+auto MatchFunctionWithBody(Args... args) -> ExpectedNode {
+  return MatchFunctionDeclaration(MatchDeclaredName(), MatchParameters(),
+                                  MatchCodeBlock(args..., MatchCodeBlockEnd()));
+}
+
 }  // namespace NodeMatchers
 
 }  // namespace Testing