From 4236da9f0284758dd9a2ca5a985bff16be43c004 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Thu, 19 Sep 2024 19:14:46 +0900
Subject: [PATCH 01/12] Bump Go version to 1.20, and add util.go

---
 ast/util.go | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 go.mod      |  2 +-
 2 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 ast/util.go

diff --git a/ast/util.go b/ast/util.go
new file mode 100644
index 00000000..8a631ee5
--- /dev/null
+++ b/ast/util.go
@@ -0,0 +1,59 @@
+package ast
+
+import (
+	"github.com/cloudspannerecosystem/memefish/token"
+	"strings"
+)
+
+// sqlOpt outputs:
+//
+//	when node != nil: left + node.SQL() + right
+//	else            : empty string
+func sqlOpt[T interface {
+	Node
+	comparable
+}](left string, node T, right string) string {
+	var zero T
+	if node == zero {
+		return ""
+	}
+	return left + node.SQL() + right
+}
+
+func lastElem[T any](s []T) T {
+	return s[len(s)-1]
+}
+
+func firstValidEnd(ns ...Node) token.Pos {
+	for _, n := range ns {
+		if n != nil && n.End() != token.InvalidPos {
+			return n.End()
+		}
+	}
+	return token.InvalidPos
+}
+
+func firstPos[T Node](s []T) token.Pos {
+	if len(s) == 0 {
+		return token.InvalidPos
+	}
+	return s[0].Pos()
+}
+
+func lastEnd[T Node](s []T) token.Pos {
+	if len(s) == 0 {
+		return token.InvalidPos
+	}
+	return lastElem(s).End()
+}
+
+func sqlJoin[T Node](elems []T, sep string) string {
+	var b strings.Builder
+	for i, r := range elems {
+		if i > 0 {
+			b.WriteString(sep)
+		}
+		b.WriteString(r.SQL())
+	}
+	return b.String()
+}
diff --git a/go.mod b/go.mod
index 0defff2e..e65f1d20 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/cloudspannerecosystem/memefish
 
-go 1.19
+go 1.20
 
 require (
 	github.com/MakeNowJust/heredoc/v2 v2.0.1

From 3f8aca2c5c51280ef94377c983058cc321a8c82f Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:04:23 +0900
Subject: [PATCH 02/12] Add comments to ast/util.go

---
 ast/util.go | 43 +++++++++++++++++++++++++++++++------------
 1 file changed, 31 insertions(+), 12 deletions(-)

diff --git a/ast/util.go b/ast/util.go
index 8a631ee5..a8ae97c8 100644
--- a/ast/util.go
+++ b/ast/util.go
@@ -5,10 +5,14 @@ import (
 	"strings"
 )
 
+// Helper functions for SQL()
+
 // sqlOpt outputs:
 //
 //	when node != nil: left + node.SQL() + right
 //	else            : empty string
+//
+// This function corresponds to sqlOpt in ast.go
 func sqlOpt[T interface {
 	Node
 	comparable
@@ -20,19 +24,42 @@ func sqlOpt[T interface {
 	return left + node.SQL() + right
 }
 
+// sqlJoin outputs joined string of SQL() of all elems by sep.
+// This function corresponds to sqlJoin in ast.go
+func sqlJoin[T Node](elems []T, sep string) string {
+	var b strings.Builder
+	for i, r := range elems {
+		if i > 0 {
+			b.WriteString(sep)
+		}
+		b.WriteString(r.SQL())
+	}
+	return b.String()
+}
+
+// Helper functions for Pos(), End()
+
+// lastElem returns last element of slice s.
+// This function corresponds to NodeSliceVar[$] in ast.go.
 func lastElem[T any](s []T) T {
 	return s[len(s)-1]
 }
 
+// firstValidEnd returns the first valid Pos() in argument.
+// "valid" means the node is not nil and Pos().Invalid() is not true.
+// This function corresponds to "(n0 ?? n1 ?? ...).End()"
 func firstValidEnd(ns ...Node) token.Pos {
 	for _, n := range ns {
-		if n != nil && n.End() != token.InvalidPos {
+		if n != nil && !n.End().Invalid() {
 			return n.End()
 		}
 	}
 	return token.InvalidPos
 }
 
+// firstPos returns the Pos() of the first node.
+// If argument is an empty slice, this function returns token.InvalidPos.
+// This function corresponds to NodeSliceVar[0].pos in ast.go.
 func firstPos[T Node](s []T) token.Pos {
 	if len(s) == 0 {
 		return token.InvalidPos
@@ -40,20 +67,12 @@ func firstPos[T Node](s []T) token.Pos {
 	return s[0].Pos()
 }
 
+// lastEnd returns the End() of the last node.
+// If argument is an empty slice, this function returns token.InvalidPos.
+// This function corresponds to NodeSliceVar[$].end in ast.go.
 func lastEnd[T Node](s []T) token.Pos {
 	if len(s) == 0 {
 		return token.InvalidPos
 	}
 	return lastElem(s).End()
 }
-
-func sqlJoin[T Node](elems []T, sep string) string {
-	var b strings.Builder
-	for i, r := range elems {
-		if i > 0 {
-			b.WriteString(sep)
-		}
-		b.WriteString(r.SQL())
-	}
-	return b.String()
-}

From 19f717d7d158d3c52bae2fc7404d986e809b3b54 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:13:34 +0900
Subject: [PATCH 03/12] Add strOpt in ast/util.go

---
 ast/util.go | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/ast/util.go b/ast/util.go
index a8ae97c8..92229a72 100644
--- a/ast/util.go
+++ b/ast/util.go
@@ -24,6 +24,19 @@ func sqlOpt[T interface {
 	return left + node.SQL() + right
 }
 
+// strOpt outputs:
+//
+//	when pred == true: s
+//	else            : empty string
+//
+// This function corresponds to {{if pred}}s{{end}} in ast.go
+func strOpt(pred bool, s string) string {
+	if pred {
+		return s
+	}
+	return ""
+}
+
 // sqlJoin outputs joined string of SQL() of all elems by sep.
 // This function corresponds to sqlJoin in ast.go
 func sqlJoin[T Node](elems []T, sep string) string {

From b0c66585a8869439834c3103b1f9437e77883459 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:13:51 +0900
Subject: [PATCH 04/12] Refactor (*CallExpr).SQL()

---
 ast/sql.go | 26 +++++---------------------
 1 file changed, 5 insertions(+), 21 deletions(-)

diff --git a/ast/sql.go b/ast/sql.go
index ad5e7193..5ff362f7 100644
--- a/ast/sql.go
+++ b/ast/sql.go
@@ -464,27 +464,11 @@ func (i *IndexExpr) SQL() string {
 }
 
 func (c *CallExpr) SQL() string {
-	sql := c.Func.SQL() + "("
-	if c.Distinct {
-		sql += "DISTINCT "
-	}
-	for i, a := range c.Args {
-		if i != 0 {
-			sql += ", "
-		}
-		sql += a.SQL()
-	}
-	if len(c.Args) > 0 && len(c.NamedArgs) > 0 {
-		sql += ", "
-	}
-	for i, v := range c.NamedArgs {
-		if i != 0 {
-			sql += ", "
-		}
-		sql += v.SQL()
-	}
-	sql += ")"
-	return sql
+	return c.Func.SQL() + "(" + strOpt(c.Distinct, "DISTINCT ") +
+		sqlJoin(c.Args, ", ") +
+		strOpt(len(c.Args) > 0 && len(c.NamedArgs) > 0, ", ") +
+		sqlJoin(c.NamedArgs, ", ") +
+		")"
 }
 
 func (n *NamedArg) SQL() string { return n.Name.SQL() + " => " + n.Value.SQL() }

From 50c42040f698a3eb37bd9adc95fa5956b5f33194 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:17:18 +0900
Subject: [PATCH 05/12] Refactor (*Select).SQL()

---
 ast/sql.go | 40 ++++++++++------------------------------
 1 file changed, 10 insertions(+), 30 deletions(-)

diff --git a/ast/sql.go b/ast/sql.go
index 5ff362f7..6a3dc360 100644
--- a/ast/sql.go
+++ b/ast/sql.go
@@ -116,36 +116,16 @@ func (c *CTE) SQL() string {
 }
 
 func (s *Select) SQL() string {
-	sql := "SELECT "
-	if s.Distinct {
-		sql += "DISTINCT "
-	}
-	if s.AsStruct {
-		sql += "AS STRUCT "
-	}
-	sql += s.Results[0].SQL()
-	for _, r := range s.Results[1:] {
-		sql += ", " + r.SQL()
-	}
-	if s.From != nil {
-		sql += " " + s.From.SQL()
-	}
-	if s.Where != nil {
-		sql += " " + s.Where.SQL()
-	}
-	if s.GroupBy != nil {
-		sql += " " + s.GroupBy.SQL()
-	}
-	if s.Having != nil {
-		sql += " " + s.Having.SQL()
-	}
-	if s.OrderBy != nil {
-		sql += " " + s.OrderBy.SQL()
-	}
-	if s.Limit != nil {
-		sql += " " + s.Limit.SQL()
-	}
-	return sql
+	return "SELECT " +
+		strOpt(s.Distinct, "DISTINCT ") +
+		strOpt(s.AsStruct, "AS STRUCT ") +
+		sqlJoin(s.Results, ", ") +
+		sqlOpt(" ", s.From, "") +
+		sqlOpt(" ", s.Where, "") +
+		sqlOpt(" ", s.GroupBy, "") +
+		sqlOpt(" ", s.Having, "") +
+		sqlOpt(" ", s.OrderBy, "") +
+		sqlOpt(" ", s.Limit, "")
 }
 
 func (c *CompoundQuery) SQL() string {

From 803f45ed7b5498307df55b2af7c5df7639f02966 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:19:22 +0900
Subject: [PATCH 06/12] Refactor (*Select).End()

---
 ast/pos.go | 20 +-------------------
 1 file changed, 1 insertion(+), 19 deletions(-)

diff --git a/ast/pos.go b/ast/pos.go
index 4e3ebb3b..fe90b554 100644
--- a/ast/pos.go
+++ b/ast/pos.go
@@ -39,25 +39,7 @@ func (c *CTE) End() token.Pos { return c.Rparen + 1 }
 func (s *Select) Pos() token.Pos { return s.Select }
 
 func (s *Select) End() token.Pos {
-	if s.Limit != nil {
-		return s.Limit.End()
-	}
-	if s.OrderBy != nil {
-		return s.OrderBy.End()
-	}
-	if s.Having != nil {
-		return s.Having.End()
-	}
-	if s.GroupBy != nil {
-		return s.GroupBy.End()
-	}
-	if s.Where != nil {
-		return s.Where.End()
-	}
-	if s.From != nil {
-		return s.From.End()
-	}
-	return s.Results[len(s.Results)-1].End()
+	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, lastElem(s.Results))
 }
 
 func (c *CompoundQuery) Pos() token.Pos {

From 18d6085bee121dc9565759a616138ef8ceffde66 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Thu, 19 Sep 2024 22:48:23 +0900
Subject: [PATCH 07/12] Bump Go version in .github/workflows

---
 .github/workflows/go.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
index d34a5425..c8197beb 100644
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -11,10 +11,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - name: Set up Go 1.19
-      uses: actions/setup-go@v5
+    - name: Set up Go 1.20
+      uses: actions/setup-go@v4
       with:
-        go-version: 1.19
+        go-version: "1.20"
       id: go
 
     - name: Check out code into the Go module directory

From 9decfc94f55ae0e83d892aa40e0efc1df74abd41 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:39:57 +0900
Subject: [PATCH 08/12] Refactor (*Path).Pos(), (*Path).End()

---
 ast/pos.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ast/pos.go b/ast/pos.go
index fe90b554..dda56a3f 100644
--- a/ast/pos.go
+++ b/ast/pos.go
@@ -358,8 +358,8 @@ func (p *Param) End() token.Pos { return p.Atmark + 1 + token.Pos(len(p.Name)) }
 func (i *Ident) Pos() token.Pos { return i.NamePos }
 func (i *Ident) End() token.Pos { return i.NameEnd }
 
-func (p *Path) Pos() token.Pos { return p.Idents[0].Pos() }
-func (p *Path) End() token.Pos { return p.Idents[len(p.Idents)-1].End() }
+func (p *Path) Pos() token.Pos { return firstPos(p.Idents) }
+func (p *Path) End() token.Pos { return lastEnd(p.Idents) }
 
 func (a *ArrayLiteral) Pos() token.Pos {
 	if !a.Array.Invalid() {

From 94a198a7920a2dab096b4b3cd3b245bcf3cfafc7 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Sun, 29 Sep 2024 15:40:55 +0900
Subject: [PATCH 09/12] Refactor (*Path).SQL()

---
 ast/sql.go | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/ast/sql.go b/ast/sql.go
index 6a3dc360..a80a5539 100644
--- a/ast/sql.go
+++ b/ast/sql.go
@@ -559,11 +559,7 @@ func (i *Ident) SQL() string {
 }
 
 func (p *Path) SQL() string {
-	sql := p.Idents[0].SQL()
-	for _, id := range p.Idents[1:] {
-		sql += "." + id.SQL()
-	}
-	return sql
+	return sqlJoin(p.Idents, ".")
 }
 
 func (a *ArrayLiteral) SQL() string {

From e1a3e815ecd3fca895317482ec3d072e999d1eb5 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Tue, 15 Oct 2024 14:07:32 +0900
Subject: [PATCH 10/12] Remove lastElem

---
 ast/pos.go  | 2 +-
 ast/util.go | 8 +-------
 2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/ast/pos.go b/ast/pos.go
index b952ea9e..458aa1ce 100644
--- a/ast/pos.go
+++ b/ast/pos.go
@@ -39,7 +39,7 @@ func (c *CTE) End() token.Pos { return c.Rparen + 1 }
 func (s *Select) Pos() token.Pos { return s.Select }
 
 func (s *Select) End() token.Pos {
-	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, lastElem(s.Results))
+	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, s.Results[len(s.Results)-1])
 }
 
 func (c *CompoundQuery) Pos() token.Pos {
diff --git a/ast/util.go b/ast/util.go
index 92229a72..0bbbff6d 100644
--- a/ast/util.go
+++ b/ast/util.go
@@ -52,12 +52,6 @@ func sqlJoin[T Node](elems []T, sep string) string {
 
 // Helper functions for Pos(), End()
 
-// lastElem returns last element of slice s.
-// This function corresponds to NodeSliceVar[$] in ast.go.
-func lastElem[T any](s []T) T {
-	return s[len(s)-1]
-}
-
 // firstValidEnd returns the first valid Pos() in argument.
 // "valid" means the node is not nil and Pos().Invalid() is not true.
 // This function corresponds to "(n0 ?? n1 ?? ...).End()"
@@ -87,5 +81,5 @@ func lastEnd[T Node](s []T) token.Pos {
 	if len(s) == 0 {
 		return token.InvalidPos
 	}
-	return lastElem(s).End()
+	return s[len(s)-1].End()
 }

From aa8820b0c6386e539898403cd4fb16a67485126e Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Tue, 15 Oct 2024 16:16:24 +0900
Subject: [PATCH 11/12] Revert "Remove lastElem"

This reverts commit e1a3e815ecd3fca895317482ec3d072e999d1eb5.
---
 ast/pos.go  | 2 +-
 ast/util.go | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/ast/pos.go b/ast/pos.go
index 458aa1ce..b952ea9e 100644
--- a/ast/pos.go
+++ b/ast/pos.go
@@ -39,7 +39,7 @@ func (c *CTE) End() token.Pos { return c.Rparen + 1 }
 func (s *Select) Pos() token.Pos { return s.Select }
 
 func (s *Select) End() token.Pos {
-	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, s.Results[len(s.Results)-1])
+	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, lastElem(s.Results))
 }
 
 func (c *CompoundQuery) Pos() token.Pos {
diff --git a/ast/util.go b/ast/util.go
index 0bbbff6d..92229a72 100644
--- a/ast/util.go
+++ b/ast/util.go
@@ -52,6 +52,12 @@ func sqlJoin[T Node](elems []T, sep string) string {
 
 // Helper functions for Pos(), End()
 
+// lastElem returns last element of slice s.
+// This function corresponds to NodeSliceVar[$] in ast.go.
+func lastElem[T any](s []T) T {
+	return s[len(s)-1]
+}
+
 // firstValidEnd returns the first valid Pos() in argument.
 // "valid" means the node is not nil and Pos().Invalid() is not true.
 // This function corresponds to "(n0 ?? n1 ?? ...).End()"
@@ -81,5 +87,5 @@ func lastEnd[T Node](s []T) token.Pos {
 	if len(s) == 0 {
 		return token.InvalidPos
 	}
-	return s[len(s)-1].End()
+	return lastElem(s).End()
 }

From 47ea7094bc4ac09ecce9ef99bb7ce995f743d0e5 Mon Sep 17 00:00:00 2001
From: apstndb <803393+apstndb@users.noreply.github.com>
Date: Tue, 15 Oct 2024 16:24:25 +0900
Subject: [PATCH 12/12] Re-organize helper functions

---
 ast/pos.go  | 47 ++++++++++++++++++++++++++-
 ast/sql.go  | 51 ++++++++++++++++++++++++++++++
 ast/util.go | 91 -----------------------------------------------------
 3 files changed, 97 insertions(+), 92 deletions(-)
 delete mode 100644 ast/util.go

diff --git a/ast/pos.go b/ast/pos.go
index b952ea9e..c817c775 100644
--- a/ast/pos.go
+++ b/ast/pos.go
@@ -4,6 +4,51 @@ import (
 	"github.com/cloudspannerecosystem/memefish/token"
 )
 
+// ================================================================================
+//
+// Helper functions for Pos(), End()
+// These functions are intended for use within this file only.
+//
+// ================================================================================
+
+// lastNode returns last element of Node slice.
+// This function corresponds to NodeSliceVar[$] in ast.go.
+func lastNode[T Node](s []T) T {
+	return s[len(s)-1]
+}
+
+// firstValidEnd returns the first valid Pos() in argument.
+// "valid" means the node is not nil and Pos().Invalid() is not true.
+// This function corresponds to "(n0 ?? n1 ?? ...).End()"
+func firstValidEnd(ns ...Node) token.Pos {
+	for _, n := range ns {
+		if n != nil && !n.End().Invalid() {
+			return n.End()
+		}
+	}
+	return token.InvalidPos
+}
+
+// firstPos returns the Pos() of the first node.
+// If argument is an empty slice, this function returns token.InvalidPos.
+// This function corresponds to NodeSliceVar[0].pos in ast.go.
+func firstPos[T Node](s []T) token.Pos {
+	if len(s) == 0 {
+		return token.InvalidPos
+	}
+	return s[0].Pos()
+}
+
+// lastEnd returns the End() of the last node.
+// If argument is an empty slice, this function returns token.InvalidPos.
+// This function corresponds to NodeSliceVar[$].end in ast.go.
+func lastEnd[T Node](s []T) token.Pos {
+	if len(s) == 0 {
+		return token.InvalidPos
+	}
+	return lastNode(s).End()
+}
+
 // ================================================================================
 //
 // SELECT
@@ -39,7 +84,7 @@ func (c *CTE) End() token.Pos { return c.Rparen + 1 }
 func (s *Select) Pos() token.Pos { return s.Select }
 
 func (s *Select) End() token.Pos {
-	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, lastElem(s.Results))
+	return firstValidEnd(s.Limit, s.OrderBy, s.Having, s.GroupBy, s.Where, s.From, lastNode(s.Results))
 }
 
 func (c *CompoundQuery) Pos() token.Pos {
diff --git a/ast/sql.go b/ast/sql.go
index 82eb6cdc..2cb2c744 100644
--- a/ast/sql.go
+++ b/ast/sql.go
@@ -2,8 +2,59 @@ package ast
 
 import (
 	"github.com/cloudspannerecosystem/memefish/token"
+	"strings"
 )
 
+// ================================================================================
+//
+// Helper functions for SQL()
+// These functions are intended for use within this file only.
+//
+// ================================================================================
+
+// sqlOpt outputs:
+//
+//	when node != nil: left + node.SQL() + right
+//	else            : empty string
+//
+// This function corresponds to sqlOpt in ast.go
+func sqlOpt[T interface {
+	Node
+	comparable
+}](left string, node T, right string) string {
+	var zero T
+	if node == zero {
+		return ""
+	}
+	return left + node.SQL() + right
+}
+
+// strOpt outputs:
+//
+//	when pred == true: s
+//	else            : empty string
+//
+// This function corresponds to {{if pred}}s{{end}} in ast.go
+func strOpt(pred bool, s string) string {
+	if pred {
+		return s
+	}
+	return ""
+}
+
+// sqlJoin outputs joined string of SQL() of all elems by sep.
+// This function corresponds to sqlJoin in ast.go
+func sqlJoin[T Node](elems []T, sep string) string {
+	var b strings.Builder
+	for i, r := range elems {
+		if i > 0 {
+			b.WriteString(sep)
+		}
+		b.WriteString(r.SQL())
+	}
+	return b.String()
+}
+
 type prec int
 
 const (
diff --git a/ast/util.go b/ast/util.go
deleted file mode 100644
index 92229a72..00000000
--- a/ast/util.go
+++ /dev/null
@@ -1,91 +0,0 @@
-package ast
-
-import (
-	"github.com/cloudspannerecosystem/memefish/token"
-	"strings"
-)
-
-// Helper functions for SQL()
-
-// sqlOpt outputs:
-//
-//	when node != nil: left + node.SQL() + right
-//	else            : empty string
-//
-// This function corresponds to sqlOpt in ast.go
-func sqlOpt[T interface {
-	Node
-	comparable
-}](left string, node T, right string) string {
-	var zero T
-	if node == zero {
-		return ""
-	}
-	return left + node.SQL() + right
-}
-
-// strOpt outputs:
-//
-//	when pred == true: s
-//	else            : empty string
-//
-// This function corresponds to {{if pred}}s{{end}} in ast.go
-func strOpt(pred bool, s string) string {
-	if pred {
-		return s
-	}
-	return ""
-}
-
-// sqlJoin outputs joined string of SQL() of all elems by sep.
-// This function corresponds to sqlJoin in ast.go
-func sqlJoin[T Node](elems []T, sep string) string {
-	var b strings.Builder
-	for i, r := range elems {
-		if i > 0 {
-			b.WriteString(sep)
-		}
-		b.WriteString(r.SQL())
-	}
-	return b.String()
-}
-
-// Helper functions for Pos(), End()
-
-// lastElem returns last element of slice s.
-// This function corresponds to NodeSliceVar[$] in ast.go.
-func lastElem[T any](s []T) T {
-	return s[len(s)-1]
-}
-
-// firstValidEnd returns the first valid Pos() in argument.
-// "valid" means the node is not nil and Pos().Invalid() is not true.
-// This function corresponds to "(n0 ?? n1 ?? ...).End()"
-func firstValidEnd(ns ...Node) token.Pos {
-	for _, n := range ns {
-		if n != nil && !n.End().Invalid() {
-			return n.End()
-		}
-	}
-	return token.InvalidPos
-}
-
-// firstPos returns the Pos() of the first node.
-// If argument is an empty slice, this function returns token.InvalidPos.
-// This function corresponds to NodeSliceVar[0].pos in ast.go.
-func firstPos[T Node](s []T) token.Pos {
-	if len(s) == 0 {
-		return token.InvalidPos
-	}
-	return s[0].Pos()
-}
-
-// lastEnd returns the End() of the last node.
-// If argument is an empty slice, this function returns token.InvalidPos.
-// This function corresponds to NodeSliceVar[$].end in ast.go.
-func lastEnd[T Node](s []T) token.Pos {
-	if len(s) == 0 {
-		return token.InvalidPos
-	}
-	return lastElem(s).End()
-}