mysql: support to infer type of a duplicated arg (#615)

Fix for issue with WHERE clause in mysql (old parser) does not parse a
parameters type correctly in certain circumstances.
Such as:
`SELECT * FROM tablex WHERE (id = sqlc.arg(id) OR sqlc.arg(id) = 0);`
This type of statement is a simple way to conditionally filter by input
arg, so that you do not have to define a GetX and a GetXbyID.
(This is a simplified example)

In sqlc v1.4.0 the second id argument gets parsed and added to the
params struct as `ID_2` but is not given a type.
This causes compile-time errors.

Because of the way parameters are parsed and added to the params struct
this fix only works when you define the parameters as sqlc.args(x)
not with `?` or `:x`.

Co-authored-by: Jessica Bellon <10819486+JessTheBell@users.noreply.github.com>
Co-authored-by: Kyle Conroy <kyle@conroy.org>

Author: JessBellon

internal/endtoend/testdata/mysql_dupl_param_name/go/db.go

@@ -0,0 +1,17 @@
+/* name: SelectUserArg :many */
+SELECT  first_name from
+users where (sqlc.arg(id) = id OR sqlc.arg(id) = 0);
+
+
+
+
+/* The following do not work with current impl */
+
+/* name: SelectUserColon :many */
+/* SELECT  first_name from */
+/* users where (:id = id OR :id = 0); */
+
+
+/* name: SelectUserQuestion :many */
+/* SELECT  first_name from */
+/* users where (? = id OR  ? = 0); */

internal/endtoend/testdata/mysql_dupl_param_name/go/models.go

@@ -0,0 +1,5 @@
+CREATE TABLE users (
+    id integer NOT NULL AUTO_INCREMENT PRIMARY KEY,
+    first_name varchar(255) NOT NULL,
+    last_name varchar(255)
+) ENGINE=InnoDB;

internal/endtoend/testdata/mysql_dupl_param_name/go/query.sql.go

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "name": "querytest",
+      "path": "go",
+      "schema": "schema.sql",
+      "queries": "query.sql",
+      "engine": "mysql"
+    }
+  ]
+}

internal/endtoend/testdata/mysql_dupl_param_name/query.sql

@@ -127,6 +127,20 @@ func (r *Result) GoQueries(settings config.CombinedSettings) []golang.Query {
 
 			structInfo := make([]structParams, len(query.Params))
 			for i := range query.Params {
+				qp := query.Params[i]
+				if qp.Typ == "" {
+					// if the param doesn't have a type, check to see if there is
+					// another param with the same name that does have a type.
+					// Because of the way params are parsed and named this only works for sqlc.arg(x) named params, not :x or ?
+					func(ps []*Param) {
+						for j := range ps {
+							if ps[j].OriginalName == qp.OriginalName &&
+								ps[j].Typ != "" {
+								query.Params[i].Typ = ps[j].Typ
+							}
+						}
+					}(query.Params)
+				}
 				structInfo[i] = structParams{
 					originalName: query.Params[i].Name,
 					goType:       query.Params[i].Typ,