syntax: make StmtList a Node

It's not particularly useful yet, but it will be useful very soon to
clean up IfClause.

We also did have Pos and End methods for this type, though we hadn't
exported them. Removing the type or the methods would be a net loss of
simplicity in the syntax tree type definitions, so properly expose the
type and methods.

It's the first node whose Pos and End methods don't take pointer
receivers. That's fine, as it is often used as an anonymous field.

syntax/nodes.go

@@ -23,7 +23,7 @@ type Node interface {
 type File struct {
 	Name string
 
-	StmtList
+	StmtList // exposing its Pos and End methods
 }
 
 // StmtList is a list of statements with any number of trailing comments. Both
@@ -33,7 +33,7 @@ type StmtList struct {
 	Last  []Comment
 }
 
-func (s StmtList) pos() Pos {
+func (s StmtList) Pos() Pos {
 	if len(s.Stmts) > 0 {
 		s := s.Stmts[0]
 		sPos := s.Pos()
@@ -50,7 +50,7 @@ func (s StmtList) pos() Pos {
 	return Pos{}
 }
 
-func (s StmtList) end() Pos {
+func (s StmtList) End() Pos {
 	if len(s.Last) > 0 {
 		return s.Last[len(s.Last)-1].End()
 	}
@@ -100,9 +100,6 @@ func (p Pos) IsValid() bool { return p.line > 0 }
 // version of p.Offset() > p2.Offset().
 func (p Pos) After(p2 Pos) bool { return p.offs > p2.offs }
 
-func (f *File) Pos() Pos { return f.StmtList.pos() }
-func (f *File) End() Pos { return f.StmtList.end() }
-
 func posAddCol(p Pos, n int) Pos {
 	p.col += uint16(n)
 	p.offs += uint32(n)
@@ -288,7 +285,7 @@ func (s *Subshell) Pos() Pos { return s.Lparen }
 func (s *Subshell) End() Pos { return posAddCol(s.Rparen, 1) }
 
 // Block represents a series of commands that should be executed in a nested
-// scope.
+// scope. It is essentially a StmtList within curly braces.
 type Block struct {
 	Lbrace, Rbrace Pos
 	StmtList
@@ -690,7 +687,7 @@ func (c *CaseItem) End() Pos {
 	if c.OpPos.IsValid() {
 		return posAddCol(c.OpPos, len(c.Op.String()))
 	}
-	return c.StmtList.end()
+	return c.StmtList.End()
 }
 
 // TestClause represents a Bash extended test clause.

syntax/printer.go

@@ -888,7 +888,7 @@ func (p *Printer) command(cmd Command, redirs []*Redirect) (startRedirs int) {
 	case *Subshell:
 		p.WriteByte('(')
 		p.wantSpace = len(x.Stmts) > 0 && startsWithLparen(x.Stmts[0])
-		p.spacePad(x.StmtList.pos())
+		p.spacePad(x.StmtList.Pos())
 		p.nestedStmts(x.StmtList, x.Rparen)
 		p.wantSpace = false
 		p.spacePad(x.Rparen)
@@ -985,8 +985,8 @@ func (p *Printer) command(cmd Command, redirs []*Redirect) (startRedirs int) {
 			p.casePatternJoin(ci.Patterns)
 			p.WriteByte(')')
 			p.wantSpace = !p.minify
-			sep := len(ci.Stmts) > 1 || ci.StmtList.pos().Line() > p.line ||
-				(!ci.StmtList.empty() && ci.OpPos.Line() > ci.StmtList.end().Line())
+			sep := len(ci.Stmts) > 1 || ci.StmtList.Pos().Line() > p.line ||
+				(!ci.StmtList.empty() && ci.OpPos.Line() > ci.StmtList.End().Line())
 			p.nestedStmts(ci.StmtList, ci.OpPos)
 			p.level++
 			if !p.minify || i != len(x.Items)-1 {
@@ -1262,7 +1262,7 @@ func (p *Printer) nestedStmts(sl StmtList, closing Pos) {
 		//     { stmt; stmt; }
 		p.wantNewline = true
 	case closing.Line() > p.line && len(sl.Stmts) > 0 &&
-		sl.end().Line() < closing.Line():
+		sl.End().Line() < closing.Line():
 		// Force a newline if we find:
 		//     { stmt
 		//     }