MDEV-9170 Get rid of LEX::length and LEX::dec

A preparatory task for:
  MDEV-4912 Add a plugin to field types (column types)

sql/item_func.h

@@ -2039,6 +2039,33 @@ enum Cast_target
 };
 
 
+struct Lex_cast_type_st: public Lex_length_and_dec_st
+{
+private:
+  Cast_target m_type;
+public:
+  void set(Cast_target type, const char *length, const char *dec)
+  {
+    m_type= type;
+    Lex_length_and_dec_st::set(length, dec);
+  }
+  void set(Cast_target type, Lex_length_and_dec_st length_and_dec)
+  {
+    m_type= type;
+    Lex_length_and_dec_st::operator=(length_and_dec);
+  }
+  void set(Cast_target type, const char *length)
+  {
+    set(type, length, 0);
+  }
+  void set(Cast_target type)
+  {
+    set(type, 0, 0);
+  }
+  Cast_target type() const { return m_type; }
+};
+
+
 class Item_func_row_count :public Item_int_func
 {
 public:

sql/sql_lex.cc

@@ -506,7 +506,6 @@ void lex_start(THD *thd)
   lex->parsing_options.reset();
   lex->empty_field_list_on_rset= 0;
   lex->select_lex.select_number= 1;
-  lex->length=0;
   lex->part_info= 0;
   lex->select_lex.in_sum_expr=0;
   lex->select_lex.ftfunc_list_alloc.empty();

sql/sql_lex.h

@@ -2396,7 +2396,6 @@ struct LEX: public Query_tables_list
   Explain_query *explain;
 
   // type information
-  char *length,*dec;
   CHARSET_INFO *charset;
 
   LEX_STRING name;
@@ -2856,7 +2855,7 @@ struct LEX: public Query_tables_list
   void restore_set_statement_var();
 
   void init_last_field(Create_field *field, const char *name, CHARSET_INFO *cs);
-  void set_last_field_type(enum enum_field_types type);
+  void set_last_field_type(const Lex_field_type_st &type);
   bool set_bincmp(CHARSET_INFO *cs, bool bin);
   // Check if "KEY IF NOT EXISTS name" used outside of ALTER context
   bool check_add_key(DDL_options_st ddl)

sql/structs.h

@@ -550,4 +550,74 @@ class DDL_options: public DDL_options_st
 };
 
 
+struct Lex_length_and_dec_st
+{
+private:
+  const char *m_length;
+  const char *m_dec;
+public:
+  void set(const char *length, const char *dec)
+  {
+    m_length= length;
+    m_dec= dec;
+  }
+  const char *length() const { return m_length; }
+  const char *dec() const { return m_dec; }
+};
+
+
+struct Lex_field_type_st: public Lex_length_and_dec_st
+{
+private:
+  enum_field_types m_type;
+  void set(enum_field_types type, const char *length, const char *dec)
+  {
+    m_type= type;
+    Lex_length_and_dec_st::set(length, dec);
+  }
+public:
+  void set(enum_field_types type, Lex_length_and_dec_st length_and_dec)
+  {
+    m_type= type;
+    Lex_length_and_dec_st::operator=(length_and_dec);
+  }
+  void set(enum_field_types type, const char *length)
+  {
+    set(type, length, 0);
+  }
+  void set(enum_field_types type)
+  {
+    set(type, 0, 0);
+  }
+  enum_field_types field_type() const { return m_type; }
+};
+
+
+struct Lex_dyncol_type_st: public Lex_length_and_dec_st
+{
+private:
+  int m_type; // enum_dynamic_column_type is not visible here, so use int
+public:
+  void set(int type, const char *length, const char *dec)
+  {
+    m_type= type;
+    Lex_length_and_dec_st::set(length, dec);
+  }
+  void set(int type, Lex_length_and_dec_st length_and_dec)
+  {
+    m_type= type;
+    Lex_length_and_dec_st::operator=(length_and_dec);
+  }
+  void set(int type, const char *length)
+  {
+    set(type, length, 0);
+  }
+  void set(int type)
+  {
+    set(type, 0, 0);
+  }
+  int dyncol_type() const { return m_type; }
+};
+
+
 #endif /* STRUCTS_INCLUDED */