libgo: update to go1.15rc1

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/245157

3 files changed, 30 insertions, 10 deletions

diff --git a/libgo/go/fmt/fmt_test.go b/libgo/go/fmt/fmt_test.go
index b9e3bc6..550c196 100644
--- a/libgo/go/fmt/fmt_test.go
+++ b/libgo/go/fmt/fmt_test.go
@@ -236,10 +236,10 @@ var fmtTests = []struct {
 	{"%#q", "\U0010ffff", "`􏿿`"},
 	{"%#+q", "\U0010ffff", "`􏿿`"},
 	// Runes that are not valid.
-	{"%q", string(0x110000), `"�"`},
-	{"%+q", string(0x110000), `"\ufffd"`},
-	{"%#q", string(0x110000), "`�`"},
-	{"%#+q", string(0x110000), "`�`"},
+	{"%q", string(rune(0x110000)), `"�"`},
+	{"%+q", string(rune(0x110000)), `"\ufffd"`},
+	{"%#q", string(rune(0x110000)), "`�`"},
+	{"%#+q", string(rune(0x110000)), "`�`"},
 
 	// characters
 	{"%c", uint('x'), "x"},
@@ -463,6 +463,15 @@ var fmtTests = []struct {
 	{"%#.4x", 1.0, "0x1.0000p+00"},
 	{"%#.4g", 1.0, "1.000"},
 	{"%#.4g", 100000.0, "1.000e+05"},
+	{"%#.4g", 1.234, "1.234"},
+	{"%#.4g", 0.1234, "0.1234"},
+	{"%#.4g", 1.23, "1.230"},
+	{"%#.4g", 0.123, "0.1230"},
+	{"%#.4g", 1.2, "1.200"},
+	{"%#.4g", 0.12, "0.1200"},
+	{"%#.4g", 10.2, "10.20"},
+	{"%#.4g", 0.0, "0.000"},
+	{"%#.4g", 0.012, "0.01200"},
 	{"%#.0f", 123.0, "123."},
 	{"%#.0e", 123.0, "1.e+02"},
 	{"%#.0x", 123.0, "0x1.p+07"},
@@ -1459,7 +1468,7 @@ func (flagPrinter) Format(f State, c rune) {
 	s := "%"
 	for i := 0; i < 128; i++ {
 		if f.Flag(i) {
-			s += string(i)
+			s += string(rune(i))
 		}
 	}
 	if w, ok := f.Width(); ok {
diff --git a/libgo/go/fmt/format.go b/libgo/go/fmt/format.go
index 74e600c..4d12f82 100644
--- a/libgo/go/fmt/format.go
+++ b/libgo/go/fmt/format.go
@@ -536,6 +536,7 @@ func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) {
 		tail := tailBuf[:0]
 
 		hasDecimalPoint := false
+		sawNonzeroDigit := false
 		// Starting from i = 1 to skip sign at num[0].
 		for i := 1; i < len(num); i++ {
 			switch num[i] {
@@ -552,10 +553,20 @@ func (f *fmt) fmtFloat(v float64, size int, verb rune, prec int) {
 				}
 				fallthrough
 			default:
-				digits--
+				if num[i] != '0' {
+					sawNonzeroDigit = true
+				}
+				// Count significant digits after the first non-zero digit.
+				if sawNonzeroDigit {
+					digits--
+				}
 			}
 		}
 		if !hasDecimalPoint {
+			// Leading digit 0 should contribute once to digits.
+			if len(num) == 2 && num[1] == '0' {
+				digits--
+			}
 			num = append(num, '.')
 		}
 		for digits > 0 {
diff --git a/libgo/go/fmt/scan.go b/libgo/go/fmt/scan.go
index 8cab018..3815770 100644
--- a/libgo/go/fmt/scan.go
+++ b/libgo/go/fmt/scan.go
@@ -600,13 +600,13 @@ func (s *ss) scanNumber(digits string, haveDigits bool) string {
 // scanRune returns the next rune value in the input.
 func (s *ss) scanRune(bitSize int) int64 {
 	s.notEOF()
-	r := int64(s.getRune())
+	r := s.getRune()
 	n := uint(bitSize)
-	x := (r << (64 - n)) >> (64 - n)
-	if x != r {
+	x := (int64(r) << (64 - n)) >> (64 - n)
+	if x != int64(r) {
 		s.errorString("overflow on character value " + string(r))
 	}
-	return r
+	return int64(r)
 }
 
 // scanBasePrefix reports whether the integer begins with a base prefix