sqlsmith: allow udf params to be referenced inside udfs

Randomly generated UDFs may now reference their parameters inside the
UDF body statements.

Epic: CRDB-20370
Fixes: cockroachdb#90782

Release note: None

pkg/internal/sqlsmith/relational.go

@@ -906,7 +906,6 @@ func (s *Smither) makeCreateFunc() (cf *tree.CreateFunction, ok bool) {
 		IsSet: setof,
 	}
 
-	// TODO(harding): Allow params to be referenced in the statement body.
 	paramCnt := s.rnd.Intn(10)
 	if len(s.types.scalarTypes) == 0 {
 		paramCnt = 0
@@ -916,6 +915,7 @@ func (s *Smither) makeCreateFunc() (cf *tree.CreateFunction, ok bool) {
 	// TODO(100962): Set a param default value sometimes.
 	params := make(tree.FuncParams, paramCnt)
 	paramTypes := make(tree.ParamTypes, paramCnt)
+	refs := make(colRefs, paramCnt)
 	for i := 0; i < paramCnt; i++ {
 		// Do not allow collated string types. These are not supported in UDFs.
 		ptyp := s.randType()
@@ -931,6 +931,12 @@ func (s *Smither) makeCreateFunc() (cf *tree.CreateFunction, ok bool) {
 			Name: pname,
 			Typ:  ptyp,
 		}
+		refs[i] = &colRef{
+			typ: ptyp,
+			item: &tree.ColumnItem{
+				ColumnName: tree.Name(pname),
+			},
+		}
 	}
 
 	// There are up to 5 function options that may be applied to UDFs.
@@ -1013,11 +1019,11 @@ func (s *Smither) makeCreateFunc() (cf *tree.CreateFunction, ok bool) {
 		if i == stmtCnt-1 {
 			// The return type of the last statement should match the function return
 			// type.
-			if stmt, _, ok = s.makeSelect([]*types.T{rtyp}, nil /* refs */); !ok {
+			if stmt, _, ok = s.makeSelect([]*types.T{rtyp}, refs); !ok {
 				return nil, false
 			}
 		} else {
-			if stmt, _, ok = s.makeSelect(nil /* desiredTypes */, nil /* refs */); !ok {
+			if stmt, _, ok = s.makeSelect(nil /* desiredTypes */, refs); !ok {
 				continue
 			}
 		}