go/printer: follow-up on CL 802043

- more test cases
- comment fixes
- minor unrelated changes as part of investigation of issue 702

R=rsc
CC=golang-dev
https://golang.org/cl/860041

src/pkg/go/printer/nodes.go

@@ -260,7 +260,7 @@ func (p *printer) exprList(prev token.Position, list []ast.Expr, depth int, mode
 			} else if mode&periodSep == 0 {
 				p.print(blank)
 			}
-			// period-separadet list elements don't need a blank
+			// period-separated list elements don't need a blank
 		}
 
 		if isPair && size > 0 && len(list) > 1 {
@@ -676,8 +676,6 @@ func isBinary(expr ast.Expr) bool {
 // type assertions, all of which may be found in selector chains, to make them
 // parts of the chain.
 func splitSelector(expr ast.Expr) (body, suffix ast.Expr) {
-	// Rewrite call and index expressions to be a part of the selector chain so
-	// that their multiline arguments get indented correctly.
 	switch x := expr.(type) {
 	case *ast.SelectorExpr:
 		body, suffix = x.X, x.Sel
@@ -714,7 +712,8 @@ func splitSelector(expr ast.Expr) (body, suffix ast.Expr) {
 
 // Convert an expression into an expression list split at the periods of
 // selector expressions.
-func selectorExprList(expr ast.Expr) (result []ast.Expr) {
+func selectorExprList(expr ast.Expr) []ast.Expr {
+	// split expression
 	var list vector.Vector
 	for expr != nil {
 		var suffix ast.Expr
@@ -722,13 +721,14 @@ func selectorExprList(expr ast.Expr) (result []ast.Expr) {
 		list.Push(suffix)
 	}
 
-	result = make([]ast.Expr, len(list))
+	// convert expression list
+	result := make([]ast.Expr, len(list))
 	i := len(result)
 	for _, x := range list {
 		i--
 		result[i] = x.(ast.Expr)
 	}
-	return
+	return result
 }
 
 

src/pkg/go/printer/printer.go

@@ -472,7 +472,7 @@ func stripCommonPrefix(lines [][]byte) {
 		for i, line := range lines[1 : len(lines)-1] {
 			switch {
 			case isBlank(line):
-				lines[i+1] = nil
+				lines[1+i] = nil // range starts at line 1
 			case prefix == nil:
 				prefix = commonPrefix(line, line)
 			default:
@@ -521,7 +521,7 @@ func stripCommonPrefix(lines [][]byte) {
 		} else {
 			// comment text on the first line
 			suffix := make([]byte, len(first))
-			n := 2
+			n := 2 // start after opening /*
 			for n < len(first) && first[n] <= ' ' {
 				suffix[n] = first[n]
 				n++
@@ -563,9 +563,9 @@ func stripCommonPrefix(lines [][]byte) {
 	}
 
 	// Remove the common prefix from all but the first and empty lines.
-	for i, line := range lines {
-		if i > 0 && len(line) != 0 {
-			lines[i] = line[len(prefix):]
+	for i, line := range lines[1:] {
+		if len(line) != 0 {
+			lines[1+i] = line[len(prefix):] // range starts at line 1
 		}
 	}
 }

src/pkg/go/printer/testdata/expressions.golden

@@ -473,4 +473,25 @@ func _() {
 		Method(1, 2,
 			3).
 		Thingy
+
+	_ = a.b.c
+	_ = a.
+		b.
+		c
+	_ = a.b().c
+	_ = a.
+		b().
+		c
+	_ = a.b[0].c
+	_ = a.
+		b[0].
+		c
+	_ = a.b[0:].c
+	_ = a.
+		b[0:].
+		c
+	_ = a.b.(T).c
+	_ = a.
+		b.(T).
+		c
 }

src/pkg/go/printer/testdata/expressions.input

@@ -423,19 +423,19 @@ func _() {
 		1).foo(2)
 
 	_ = Array[3 +
-		4]
+4]
 
 	_ = Method(1, 2,
 		3)
 
 	_ = new(T).
    foo().
-	bar().(*Type)
+   bar() . (*Type)
 
 	_ = new(T).
-	foo().
-	bar().(*Type).
-	baz()
+foo().
+bar().(*Type).
+baz()
 
 	_ = new(T).
 	foo().
@@ -443,7 +443,7 @@ func _() {
 
 	_ = new(T).
 	foo().
-	bar()["idx"].
+	bar()["idx"]	.
 	baz()
 
 	_ = new(T).
@@ -459,10 +459,32 @@ func _() {
 		Field.
 		Array[3+
        		4].
-		Table["foo"].
-		Blob.(*Type).
+		Table ["foo"].
+		Blob. (*Type).
 	Slices[1:4].
 	Method(1, 2,
 	3).
 		Thingy
+
+	_ = a.b.c
+	_ = a.
+	b.
+	c
+	_ = a.b().c
+	_ = a.
+	b().
+	c
+	_ = a.b[0].c
+	_ = a.
+	b[0].
+	c
+	_ = a.b[0:].c
+	_ = a.
+	b[0:].
+	c
+	_ = a.b.(T).c
+	_ = a.
+	b.
+	(T).
+	c
 }

src/pkg/go/printer/testdata/expressions.raw

@@ -473,4 +473,25 @@ func _() {
 		Method(1, 2,
 			3).
 		Thingy
+
+	_ = a.b.c
+	_ = a.
+		b.
+		c
+	_ = a.b().c
+	_ = a.
+		b().
+		c
+	_ = a.b[0].c
+	_ = a.
+		b[0].
+		c
+	_ = a.b[0:].c
+	_ = a.
+		b[0:].
+		c
+	_ = a.b.(T).c
+	_ = a.
+		b.(T).
+		c
 }