#3166 fix: allow sqlc.arg/@name to fill gaps in numbered placeholder sequences

internal/endtoend/testdata/invalid_params/pgx/v4/stderr/base.txt

@@ -2,4 +2,4 @@
 query.sql:1:1: could not determine data type of parameter $1
 query.sql:5:1: could not determine data type of parameter $2
 query.sql:8:8: column "foo" does not exist
-query.sql:11:1: could not determine data type of parameter $2
+query.sql:11:1: could not determine data type of parameter $3

internal/endtoend/testdata/invalid_params/pgx/v5/stderr/base.txt

@@ -2,4 +2,4 @@
 query.sql:1:1: could not determine data type of parameter $1
 query.sql:5:1: could not determine data type of parameter $2
 query.sql:8:8: column "foo" does not exist
-query.sql:11:1: could not determine data type of parameter $2
+query.sql:11:1: could not determine data type of parameter $3

internal/endtoend/testdata/invalid_params/stdlib/stderr/base.txt

@@ -2,4 +2,4 @@
 query.sql:1:1: could not determine data type of parameter $1
 query.sql:5:1: could not determine data type of parameter $2
 query.sql:8:8: column "foo" does not exist
-query.sql:11:1: could not determine data type of parameter $2
+query.sql:11:1: could not determine data type of parameter $3

internal/sql/preprocess/preprocess.go

@@ -215,8 +215,8 @@ func Dialected(d Dialect, src string) *Result {
 			continue
 		}
 
-		stmt.Dollar, stmt.ParamErr = validatePlaceholders(occs)
 		stmt.Params = number(d, occs)
+		stmt.Dollar, stmt.ParamErr = validatePlaceholders(occs)
 		stmt.Numbers = map[int]int{}
 
 		prev := start
@@ -301,6 +301,17 @@ func validatePlaceholders(occs []occurrence) (dollar bool, err error) {
 			unnumbered = true
 		}
 	}
+
+	// sqlc.arg/narg/slice fill gaps in numbered dialects; include them so
+	// the gap check does not fire for positions they occupy.
+	if numbered && !unnumbered {
+		for _, occ := range occs {
+			if occ.kind == kindArg || occ.kind == kindNarg || occ.kind == kindSlice {
+				seen[occ.number] = true
+			}
+		}
+	}
+
 	if numbered && unnumbered {
 		return false, errors.New("can not mix $1 format with ? format")
 	}

internal/sql/preprocess/testdata/postgresql/arg_fills_gap_at_start/input.sql

@@ -0,0 +1 @@
+INSERT INTO users (a, b, c) VALUES (sqlc.arg(a), @b, $3);

internal/sql/preprocess/testdata/postgresql/arg_fills_gap_at_start/output.sql

@@ -0,0 +1 @@
+INSERT INTO users (a, b, c) VALUES ($1, $2, $3);

internal/sql/preprocess/testdata/postgresql/arg_fills_gap_at_start/side_table.json

@@ -0,0 +1,29 @@
+[
+  {
+    "start": 0,
+    "end": 48,
+    "dollar": true,
+    "params": [
+      {
+        "number": 1,
+        "location": 36,
+        "origin": 36,
+        "name": "a",
+        "named": true
+      },
+      {
+        "number": 2,
+        "location": 40,
+        "origin": 49,
+        "name": "b",
+        "named": true
+      },
+      {
+        "number": 3,
+        "location": 44,
+        "origin": 53,
+        "named": false
+      }
+    ]
+  }
+]