From 2d60910e66841d0ee273748d7094e560f8e29e5e Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Fri, 17 Apr 2026 06:25:46 +0000
Subject: [PATCH] Dedupe sqlc.arg parameters wrapped in a type cast for MySQL

When a sqlc.arg() call was wrapped in a CAST (or MySQL's synthetic
MATCH...AGAINST type cast), the resulting Parameter was not marked as
named. Downstream struct-field generation then added numeric suffixes
to disambiguate identical names, producing spurious fields like
SearchTerm_3 alongside SearchTerm.

Capture the isNamed result from FetchMerge so the column correctly
reflects that it came from a named parameter, letting the code
generator reuse a single struct field for repeated sqlc.arg(name)
references.

Fixes #4376
---
 internal/compiler/resolve.go                  |  3 +-
 .../params_duplicate/mysql/go/models.go       |  1 +
 .../params_duplicate/mysql/go/query.sql.go    | 33 +++++++++++++++++++
 .../testdata/params_duplicate/mysql/query.sql |  5 +++
 .../params_duplicate/mysql/schema.sql         |  3 +-
 5 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/internal/compiler/resolve.go b/internal/compiler/resolve.go
index b1fbb1990e..d926f2b1fc 100644
--- a/internal/compiler/resolve.go
+++ b/internal/compiler/resolve.go
@@ -513,10 +513,11 @@ func (comp *Compiler) resolveCatalogRefs(qc *QueryCatalog, rvs []*ast.RangeVar,
 			}
 			col := toColumn(n.TypeName)
 			defaultP := named.NewInferredParam(col.Name, col.NotNull)
-			p, _ := params.FetchMerge(ref.ref.Number, defaultP)
+			p, isNamed := params.FetchMerge(ref.ref.Number, defaultP)
 
 			col.Name = p.Name()
 			col.NotNull = p.NotNull()
+			col.IsNamedParam = isNamed
 			a = append(a, Parameter{
 				Number: ref.ref.Number,
 				Column: col,
diff --git a/internal/endtoend/testdata/params_duplicate/mysql/go/models.go b/internal/endtoend/testdata/params_duplicate/mysql/go/models.go
index cab9171aaf..c47ceb80a6 100644
--- a/internal/endtoend/testdata/params_duplicate/mysql/go/models.go
+++ b/internal/endtoend/testdata/params_duplicate/mysql/go/models.go
@@ -12,4 +12,5 @@ type User struct {
 	ID        int32
 	FirstName sql.NullString
 	LastName  sql.NullString
+	Age       sql.NullInt32
 }
diff --git a/internal/endtoend/testdata/params_duplicate/mysql/go/query.sql.go b/internal/endtoend/testdata/params_duplicate/mysql/go/query.sql.go
index 332cb9b26e..33a8e53d75 100644
--- a/internal/endtoend/testdata/params_duplicate/mysql/go/query.sql.go
+++ b/internal/endtoend/testdata/params_duplicate/mysql/go/query.sql.go
@@ -10,6 +10,39 @@ import (
 	"database/sql"
 )
 
+const selectUserByAgeCast = `-- name: SelectUserByAgeCast :many
+SELECT first_name FROM users
+WHERE age > CAST(? AS SIGNED)
+   OR age < CAST(? AS SIGNED)
+`
+
+type SelectUserByAgeCastParams struct {
+	Threshold int64
+}
+
+func (q *Queries) SelectUserByAgeCast(ctx context.Context, arg SelectUserByAgeCastParams) ([]sql.NullString, error) {
+	rows, err := q.db.QueryContext(ctx, selectUserByAgeCast, arg.Threshold, arg.Threshold)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []sql.NullString
+	for rows.Next() {
+		var first_name sql.NullString
+		if err := rows.Scan(&first_name); err != nil {
+			return nil, err
+		}
+		items = append(items, first_name)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
 const selectUserByID = `-- name: SelectUserByID :many
 SELECT first_name from
 users where (? = id OR ? = 0)
diff --git a/internal/endtoend/testdata/params_duplicate/mysql/query.sql b/internal/endtoend/testdata/params_duplicate/mysql/query.sql
index cd661993c7..3924f57ad7 100644
--- a/internal/endtoend/testdata/params_duplicate/mysql/query.sql
+++ b/internal/endtoend/testdata/params_duplicate/mysql/query.sql
@@ -11,3 +11,8 @@ WHERE first_name = sqlc.arg(name)
 /* name: SelectUserQuestion :many */
 SELECT first_name from
 users where (? = id OR  ? = 0);
+
+/* name: SelectUserByAgeCast :many */
+SELECT first_name FROM users
+WHERE age > CAST(sqlc.arg(threshold) AS SIGNED)
+   OR age < CAST(sqlc.arg(threshold) AS SIGNED);
diff --git a/internal/endtoend/testdata/params_duplicate/mysql/schema.sql b/internal/endtoend/testdata/params_duplicate/mysql/schema.sql
index e93e087e50..497fa29b7d 100644
--- a/internal/endtoend/testdata/params_duplicate/mysql/schema.sql
+++ b/internal/endtoend/testdata/params_duplicate/mysql/schema.sql
@@ -1,5 +1,6 @@
 CREATE TABLE users (
     id integer NOT NULL AUTO_INCREMENT PRIMARY KEY,
     first_name varchar(255),
-    last_name varchar(255)
+    last_name varchar(255),
+    age int
 ) ENGINE=InnoDB;