adding comments and some newlines (#294)

* adding comments and some newlines

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* changed comment style

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

* Update executable_semantics/interpreter/typecheck.cpp

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>

executable_semantics/ast/expression.h

@@ -26,6 +26,7 @@ enum class ExpressionKind {
   TypeT,
   Variable,
 };
+
 enum class Operator {
   Add,
   And,
@@ -43,35 +44,44 @@ struct Expression {
     struct {
       std::string* name;
     } variable;
+
     struct {
       Expression* aggregate;
       std::string* field;
     } get_field;
+
     struct {
       Expression* aggregate;
       Expression* offset;
     } index;
+
     struct {
       std::string* name;
       Expression* type;
     } pattern_variable;
+
     int integer;
     bool boolean;
+
     struct {
       std::vector<std::pair<std::string, Expression*>>* fields;
     } tuple;
+
     struct {
       Operator op;
       std::vector<Expression*>* arguments;
     } primitive_op;
+
     struct {
       Expression* function;
       Expression* argument;
     } call;
+
     struct {
       Expression* parameter;
       Expression* return_type;
     } function_type;
+
   } u;
 };