go/printer: fix formatting of three-index slice expression

Apply gofmt to src, misc.

Fixes #22111.

Change-Id: Ib1bda0caaf2c1787a8137b7a61bbef7a341cc68c
Reviewed-on: https://go-review.googlesource.com/67633
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

misc/cgo/testcshared/src/p/p.go

@@ -8,5 +8,6 @@ import "C"
 
 //export FromPkg
 func FromPkg() int32 { return 1024 }
+
 //export Divu
 func Divu(a, b uint32) uint32 { return a / b }

src/go/printer/nodes.go

@@ -774,20 +774,35 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
 		if x.Max != nil {
 			indices = append(indices, x.Max)
 		}
-		for i, y := range indices {
+		// determine if we need extra blanks around ':'
+		var needsBlanks bool
+		if depth <= 1 {
+			var indexCount int
+			var hasBinaries bool
+			for _, x := range indices {
+				if x != nil {
+					indexCount++
+					if isBinary(x) {
+						hasBinaries = true
+					}
+				}
+			}
+			if indexCount > 1 && hasBinaries {
+				needsBlanks = true
+			}
+		}
+		for i, x := range indices {
 			if i > 0 {
-				// blanks around ":" if both sides exist and either side is a binary expression
-				// TODO(gri) once we have committed a variant of a[i:j:k] we may want to fine-
-				//           tune the formatting here
-				x := indices[i-1]
-				if depth <= 1 && x != nil && y != nil && (isBinary(x) || isBinary(y)) {
-					p.print(blank, token.COLON, blank)
-				} else {
+				if indices[i-1] != nil && needsBlanks {
+					p.print(blank)
+				}
 				p.print(token.COLON)
+				if x != nil && needsBlanks {
+					p.print(blank)
 				}
 			}
-			if y != nil {
-				p.expr0(y, depth+1)
+			if x != nil {
+				p.expr0(x, depth+1)
 			}
 		}
 		p.print(x.Rbrack, token.RBRACK)

src/go/printer/testdata/expressions.golden

@@ -136,6 +136,35 @@ func _() {
 	_ = x[: b+d : c+d]
 }
 
+func issue22111() {
+	_ = x[:]
+
+	_ = x[:b]
+	_ = x[:b+1]
+
+	_ = x[a:]
+	_ = x[a+1:]
+
+	_ = x[a:b]
+	_ = x[a+1 : b]
+	_ = x[a : b+1]
+	_ = x[a+1 : b+1]
+
+	_ = x[:b:c]
+	_ = x[: b+1 : c]
+	_ = x[: b : c+1]
+	_ = x[: b+1 : c+1]
+
+	_ = x[a:b:c]
+	_ = x[a+1 : b : c]
+	_ = x[a : b+1 : c]
+	_ = x[a+1 : b+1 : c]
+	_ = x[a : b : c+1]
+	_ = x[a+1 : b : c+1]
+	_ = x[a : b+1 : c+1]
+	_ = x[a+1 : b+1 : c+1]
+}
+
 func _() {
 	_ = a + b
 	_ = a + b + c

src/go/printer/testdata/expressions.input

@@ -138,6 +138,35 @@ func _() {
 	_ = x[:b+d:c+d]
 }
 
+func issue22111() {
+	_ = x[:]
+
+	_ = x[:b]
+	_ = x[:b+1]
+
+	_ = x[a:]
+	_ = x[a+1:]
+
+	_ = x[a:b]
+	_ = x[a+1:b]
+	_ = x[a:b+1]
+	_ = x[a+1:b+1]
+
+	_ = x[:b:c]
+	_ = x[:b+1:c]
+	_ = x[:b:c+1]
+	_ = x[:b+1:c+1]
+
+	_ = x[a:b:c]
+	_ = x[a+1:b:c]
+	_ = x[a:b+1:c]
+	_ = x[a+1:b+1:c]
+	_ = x[a:b:c+1]
+	_ = x[a+1:b:c+1]
+	_ = x[a:b+1:c+1]
+	_ = x[a+1:b+1:c+1]
+}
+
 func _() {
 	_ = a+b
 	_ = a+b+c

src/go/printer/testdata/expressions.raw

@@ -136,6 +136,35 @@ func _() {
 	_ = x[: b+d : c+d]
 }
 
+func issue22111() {
+	_ = x[:]
+
+	_ = x[:b]
+	_ = x[:b+1]
+
+	_ = x[a:]
+	_ = x[a+1:]
+
+	_ = x[a:b]
+	_ = x[a+1 : b]
+	_ = x[a : b+1]
+	_ = x[a+1 : b+1]
+
+	_ = x[:b:c]
+	_ = x[: b+1 : c]
+	_ = x[: b : c+1]
+	_ = x[: b+1 : c+1]
+
+	_ = x[a:b:c]
+	_ = x[a+1 : b : c]
+	_ = x[a : b+1 : c]
+	_ = x[a+1 : b+1 : c]
+	_ = x[a : b : c+1]
+	_ = x[a+1 : b : c+1]
+	_ = x[a : b+1 : c+1]
+	_ = x[a+1 : b+1 : c+1]
+}
+
 func _() {
 	_ = a + b
 	_ = a + b + c