cmd/compile: accept new Go2 number literals

This CL introduces compiler support for the new binary and octal integer
literals, hexadecimal floats, and digit separators for all number literals.

The new Go 2 number literal scanner accepts the following liberal format:

number   = [ prefix ] digits [ "." digits ] [ exponent ] [ "i" ] .
prefix   = "0" [ "b" |"B" | "o" | "O" | "x" | "X" ] .
digits   = { digit | "_" } .
exponent = ( "e" | "E" | "p" | "P" ) [ "+" | "-" ] digits .

If the number starts with "0x" or "0X", digit is any hexadecimal digit;
otherwise, digit is any decimal digit. If the accepted number is not valid,
errors are reported accordingly.

See the new test cases in scanner_test.go for a selection of valid and
invalid numbers and the respective error messages.

R=Go1.13

Updates #12711.
Updates #19308.
Updates #28493.
Updates #29008.

Change-Id: Ic8febc7bd4dc5186b16a8c8897691e81125cf0ca
Reviewed-on: https://go-review.googlesource.com/c/157677
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/compile/internal/gc/mpfloat.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"math"
 	"math/big"
+	"strings"
 )
 
 // implements float arithmetic
@@ -177,11 +178,14 @@ func (a *Mpflt) Neg() {
 }
 
 func (a *Mpflt) SetString(as string) {
+	// TODO(gri) remove this code once math/big.Float.Parse can handle separators
+	as = strings.Replace(as, "_", "", -1) // strip separators
+
 	for len(as) > 0 && (as[0] == ' ' || as[0] == '\t') {
 		as = as[1:]
 	}
 
-	f, _, err := a.Val.Parse(as, 10)
+	f, _, err := a.Val.Parse(as, 0)
 	if err != nil {
 		yyerror("malformed constant: %s (%v)", as, err)
 		a.Val.SetFloat64(0)

src/cmd/compile/internal/gc/mpint.go

@@ -7,6 +7,7 @@ package gc
 import (
 	"fmt"
 	"math/big"
+	"strings"
 )
 
 // implements integer arithmetic
@@ -281,6 +282,12 @@ func (a *Mpint) SetInt64(c int64) {
 }
 
 func (a *Mpint) SetString(as string) {
+	// TODO(gri) remove this code once math/big.Int.SetString can handle 0o-octals and separators
+	as = strings.Replace(as, "_", "", -1) // strip separators
+	if len(as) >= 2 && as[0] == '0' && (as[1] == 'o' || as[1] == 'O') {
+		as = "0" + as[2:]
+	}
+
 	_, ok := a.Val.SetString(as, 0)
 	if !ok {
 		// required syntax is [+-][0[x]]d*

src/cmd/compile/internal/syntax/scanner.go

@@ -47,6 +47,10 @@ func (s *scanner) init(src io.Reader, errh func(line, col uint, msg string), mod
 	s.nlsemi = false
 }
 
+func (s *scanner) errorf(format string, args ...interface{}) {
+	s.error(fmt.Sprintf(format, args...))
+}
+
 // next advances the scanner by reading the next token.
 //
 // If a read, source encoding, or lexical error occurs, next calls
@@ -149,8 +153,9 @@ redo:
 
 	case '.':
 		c = s.getr()
-		if isDigit(c) {
+		if isDecimal(c) {
-			s.unread(1)
+			s.ungetr()
+			s.unread(1) // correct position of '.' (needed by startLit in number)
 			s.number('.')
 			break
 		}
@@ -304,7 +309,7 @@ redo:
 
 	default:
 		s.tok = 0
-		s.error(fmt.Sprintf("invalid character %#U", c))
+		s.errorf("invalid character %#U", c)
 		goto redo
 	}
 
@@ -320,11 +325,7 @@ assignop:
 }
 
 func isLetter(c rune) bool {
-	return 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_'
+	return 'a' <= lower(c) && lower(c) <= 'z' || c == '_'
-}
-
-func isDigit(c rune) bool {
-	return '0' <= c && c <= '9'
 }
 
 func (s *scanner) ident() {
@@ -332,7 +333,7 @@ func (s *scanner) ident() {
 
 	// accelerate common case (7bit ASCII)
 	c := s.getr()
-	for isLetter(c) || isDigit(c) {
+	for isLetter(c) || isDecimal(c) {
 		c = s.getr()
 	}
 
@@ -372,10 +373,10 @@ func (s *scanner) isIdentRune(c rune, first bool) bool {
 		// ok
 	case unicode.IsDigit(c):
 		if first {
-			s.error(fmt.Sprintf("identifier cannot begin with digit %#U", c))
+			s.errorf("identifier cannot begin with digit %#U", c)
 		}
 	case c >= utf8.RuneSelf:
-		s.error(fmt.Sprintf("invalid identifier character %#U", c))
+		s.errorf("invalid identifier character %#U", c)
 	default:
 		return false
 	}
@@ -401,86 +402,188 @@ func init() {
 	}
 }
 
+func lower(c rune) rune     { return ('a' - 'A') | c } // returns lower-case c iff c is ASCII letter
+func isDecimal(c rune) bool { return '0' <= c && c <= '9' }
+func isHex(c rune) bool     { return '0' <= c && c <= '9' || 'a' <= lower(c) && lower(c) <= 'f' }
+
+// digits accepts the sequence { digit | '_' } starting with c0.
+// If base <= 10, digits accepts any decimal digit but records
+// the index (relative to the literal start) of a digit >= base
+// in *invalid, if *invalid < 0.
+// digits returns the first rune that is not part of the sequence
+// anymore, and a bitset describing whether the sequence contained
+// digits (bit 0 is set), or separators '_' (bit 1 is set).
+func (s *scanner) digits(c0 rune, base int, invalid *int) (c rune, digsep int) {
+	c = c0
+	if base <= 10 {
+		max := rune('0' + base)
+		for isDecimal(c) || c == '_' {
+			ds := 1
+			if c == '_' {
+				ds = 2
+			} else if c >= max && *invalid < 0 {
+				*invalid = int(s.col0 - s.col) // record invalid rune index
+			}
+			digsep |= ds
+			c = s.getr()
+		}
+	} else {
+		for isHex(c) || c == '_' {
+			ds := 1
+			if c == '_' {
+				ds = 2
+			}
+			digsep |= ds
+			c = s.getr()
+		}
+	}
+	return
+}
+
 func (s *scanner) number(c rune) {
 	s.startLit()
 
+	base := 10        // number base
+	prefix := rune(0) // one of 0 (decimal), '0' (0-octal), 'x', 'o', or 'b'
+	digsep := 0       // bit 0: digit present, bit 1: '_' present
+	invalid := -1     // index of invalid digit in literal, or < 0
+
+	// integer part
+	var ds int
 	if c != '.' {
-		s.kind = IntLit // until proven otherwise
+		s.kind = IntLit
 		if c == '0' {
 			c = s.getr()
-			if c == 'x' || c == 'X' {
+			switch lower(c) {
-				// hex
+			case 'x':
 				c = s.getr()
-				hasDigit := false
+				base, prefix = 16, 'x'
-				for isDigit(c) || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
+			case 'o':
-					c = s.getr()
-					hasDigit = true
-				}
-				if !hasDigit {
-					s.error("malformed hex constant")
-				}
-				goto done
-			}
-
-			// decimal 0, octal, or float
-			has8or9 := false
-			for isDigit(c) {
-				if c > '7' {
-					has8or9 = true
-				}
 				c = s.getr()
-			}
+				base, prefix = 8, 'o'
-			if c != '.' && c != 'e' && c != 'E' && c != 'i' {
+			case 'b':
-				// octal
-				if has8or9 {
-					s.error("malformed octal constant")
-				}
-				goto done
-			}
-
-		} else {
-			// decimal or float
-			for isDigit(c) {
 				c = s.getr()
+				base, prefix = 2, 'b'
+			default:
+				base, prefix = 8, '0'
+				digsep = 1 // leading 0
 			}
 		}
+		c, ds = s.digits(c, base, &invalid)
+		digsep |= ds
 	}
 
-	// float
+	// fractional part
 	if c == '.' {
 		s.kind = FloatLit
-		c = s.getr()
+		if prefix == 'o' || prefix == 'b' {
-		for isDigit(c) {
+			s.error("invalid radix point in " + litname(prefix))
-			c = s.getr()
 		}
+		c, ds = s.digits(s.getr(), base, &invalid)
+		digsep |= ds
+	}
+
+	if digsep&1 == 0 {
+		s.error(litname(prefix) + " has no digits")
 	}
 
 	// exponent
-	if c == 'e' || c == 'E' {
+	if e := lower(c); e == 'e' || e == 'p' {
-		s.kind = FloatLit
+		switch {
+		case e == 'e' && prefix != 0 && prefix != '0':
+			s.errorf("%q exponent requires decimal mantissa", c)
+		case e == 'p' && prefix != 'x':
+			s.errorf("%q exponent requires hexadecimal mantissa", c)
+		}
 		c = s.getr()
-		if c == '-' || c == '+' {
+		s.kind = FloatLit
+		if c == '+' || c == '-' {
 			c = s.getr()
 		}
-		if !isDigit(c) {
+		c, ds = s.digits(c, 10, nil)
-			s.error("malformed floating-point constant exponent")
+		digsep |= ds
-		}
+		if ds&1 == 0 {
-		for isDigit(c) {
+			s.error("exponent has no digits")
-			c = s.getr()
 		}
+	} else if prefix == 'x' && s.kind == FloatLit {
+		s.error("hexadecimal mantissa requires a 'p' exponent")
 	}
 
-	// complex
+	// suffix 'i'
 	if c == 'i' {
 		s.kind = ImagLit
-		s.getr()
+		if prefix != 0 && prefix != '0' {
+			s.error("invalid suffix 'i' on " + litname(prefix))
+		}
+		c = s.getr()
 	}
-
-done:
 	s.ungetr()
+
 	s.nlsemi = true
 	s.lit = string(s.stopLit())
 	s.tok = _Literal
+
+	if s.kind == IntLit && invalid >= 0 {
+		s.errh(s.line, s.col+uint(invalid), fmt.Sprintf("invalid digit %q in %s", s.lit[invalid], litname(prefix)))
+	}
+
+	if digsep&2 != 0 {
+		if i := invalidSep(s.lit); i >= 0 {
+			s.errh(s.line, s.col+uint(i), "'_' must separate successive digits")
+		}
+	}
+}
+
+func litname(prefix rune) string {
+	switch prefix {
+	case 'x':
+		return "hexadecimal literal"
+	case 'o', '0':
+		return "octal literal"
+	case 'b':
+		return "binary literal"
+	}
+	return "decimal literal"
+}
+
+// invalidSep returns the index of the first invalid separator in x, or -1.
+func invalidSep(x string) int {
+	x1 := ' ' // prefix char, we only care if it's 'x'
+	d := '.'  // digit, one of '_', '0' (a digit), or '.' (anything else)
+	i := 0
+
+	// a prefix counts as a digit
+	if len(x) >= 2 && x[0] == '0' {
+		x1 = lower(rune(x[1]))
+		if x1 == 'x' || x1 == 'o' || x1 == 'b' {
+			d = '0'
+			i = 2
+		}
+	}
+
+	// mantissa and exponent
+	for ; i < len(x); i++ {
+		p := d // previous digit
+		d = rune(x[i])
+		switch {
+		case d == '_':
+			if p != '0' {
+				return i
+			}
+		case isDecimal(d) || x1 == 'x' && isHex(d):
+			d = '0'
+		default:
+			if p == '_' {
+				return i - 1
+			}
+			d = '.'
+		}
+	}
+	if d == '_' {
+		return len(x) - 1
+	}
+
+	return -1
 }
 
 func (s *scanner) rune() {
@@ -713,12 +816,10 @@ func (s *scanner) escape(quote rune) bool {
 	for i := n; i > 0; i-- {
 		d := base
 		switch {
-		case isDigit(c):
+		case isDecimal(c):
 			d = uint32(c) - '0'
-		case 'a' <= c && c <= 'f':
+		case 'a' <= lower(c) && lower(c) <= 'f':
-			d = uint32(c) - ('a' - 10)
+			d = uint32(lower(c)) - ('a' - 10)
-		case 'A' <= c && c <= 'F':
-			d = uint32(c) - ('A' - 10)
 		}
 		if d >= base {
 			if c < 0 {
@@ -728,7 +829,7 @@ func (s *scanner) escape(quote rune) bool {
 			if base == 8 {
 				kind = "octal"
 			}
-			s.error(fmt.Sprintf("non-%s character in escape sequence: %c", kind, c))
+			s.errorf("non-%s character in escape sequence: %c", kind, c)
 			s.ungetr()
 			return false
 		}
@@ -739,7 +840,7 @@ func (s *scanner) escape(quote rune) bool {
 	s.ungetr()
 
 	if x > max && base == 8 {
-		s.error(fmt.Sprintf("octal escape value > 255: %d", x))
+		s.errorf("octal escape value > 255: %d", x)
 		return false
 	}
 

src/cmd/compile/internal/syntax/scanner_test.go

@@ -45,15 +45,17 @@ func TestTokens(t *testing.T) {
 	// make source
 	var buf bytes.Buffer
 	for i, s := range sampleTokens {
-		buf.WriteString("\t\t\t\t"[:i&3])           // leading indentation
+		buf.WriteString("\t\t\t\t"[:i&3])                          // leading indentation
-		buf.WriteString(s.src)                      // token
+		buf.WriteString(s.src)                                     // token
-		buf.WriteString("        "[:i&7])           // trailing spaces
+		buf.WriteString("        "[:i&7])                          // trailing spaces
-		buf.WriteString("/*line foo:1 */ // bar\n") // comments (don't crash w/o directive handler)
+		fmt.Fprintf(&buf, "/*line foo:%d */ // bar\n", i+linebase) // comments (don't crash w/o directive handler)
 	}
 
 	// scan source
 	var got scanner
-	got.init(&buf, nil, 0)
+	got.init(&buf, func(line, col uint, msg string) {
+		t.Fatalf("%d:%d: %s", line, col, msg)
+	}, 0)
 	got.next()
 	for i, want := range sampleTokens {
 		nlsemi := false
@@ -140,8 +142,16 @@ var sampleTokens = [...]struct {
 	{_Literal, "12345", 0, 0},
 	{_Literal, "123456789012345678890123456789012345678890", 0, 0},
 	{_Literal, "01234567", 0, 0},
-	{_Literal, "0x0", 0, 0},
+	{_Literal, "0_1_234_567", 0, 0},
+	{_Literal, "0X0", 0, 0},
 	{_Literal, "0xcafebabe", 0, 0},
+	{_Literal, "0x_cafe_babe", 0, 0},
+	{_Literal, "0O0", 0, 0},
+	{_Literal, "0o000", 0, 0},
+	{_Literal, "0o_000", 0, 0},
+	{_Literal, "0B1", 0, 0},
+	{_Literal, "0b01100110", 0, 0},
+	{_Literal, "0b_0110_0110", 0, 0},
 	{_Literal, "0.", 0, 0},
 	{_Literal, "0.e0", 0, 0},
 	{_Literal, "0.e-1", 0, 0},
@@ -323,6 +333,202 @@ func TestComments(t *testing.T) {
 	}
 }
 
+func TestNumbers(t *testing.T) {
+	for _, test := range []struct {
+		kind             LitKind
+		src, tokens, err string
+	}{
+		// binaries
+		{IntLit, "0b0", "0b0", ""},
+		{IntLit, "0b1010", "0b1010", ""},
+		{IntLit, "0B1110", "0B1110", ""},
+
+		{IntLit, "0b", "0b", "binary literal has no digits"},
+		{IntLit, "0b0190", "0b0190", "invalid digit '9' in binary literal"},
+		{IntLit, "0b01a0", "0b01 a0", ""}, // only accept 0-9
+
+		// binary floats and imaginaries (invalid)
+		{FloatLit, "0b.", "0b.", "invalid radix point in binary literal"},
+		{FloatLit, "0b.1", "0b.1", "invalid radix point in binary literal"},
+		{FloatLit, "0b1.0", "0b1.0", "invalid radix point in binary literal"},
+		{FloatLit, "0b1e10", "0b1e10", "'e' exponent requires decimal mantissa"},
+		{FloatLit, "0b1P-1", "0b1P-1", "'P' exponent requires hexadecimal mantissa"},
+		{ImagLit, "0b10i", "0b10i", "invalid suffix 'i' on binary literal"},
+
+		// octals
+		{IntLit, "0o0", "0o0", ""},
+		{IntLit, "0o1234", "0o1234", ""},
+		{IntLit, "0O1234", "0O1234", ""},
+
+		{IntLit, "0o", "0o", "octal literal has no digits"},
+		{IntLit, "0o8123", "0o8123", "invalid digit '8' in octal literal"},
+		{IntLit, "0o1293", "0o1293", "invalid digit '9' in octal literal"},
+		{IntLit, "0o12a3", "0o12 a3", ""}, // only accept 0-9
+
+		// octal floats and imaginaries (invalid)
+		{FloatLit, "0o.", "0o.", "invalid radix point in octal literal"},
+		{FloatLit, "0o.2", "0o.2", "invalid radix point in octal literal"},
+		{FloatLit, "0o1.2", "0o1.2", "invalid radix point in octal literal"},
+		{FloatLit, "0o1E+2", "0o1E+2", "'E' exponent requires decimal mantissa"},
+		{FloatLit, "0o1p10", "0o1p10", "'p' exponent requires hexadecimal mantissa"},
+		{ImagLit, "0o10i", "0o10i", "invalid suffix 'i' on octal literal"},
+
+		// 0-octals
+		{IntLit, "0", "0", ""},
+		{IntLit, "0123", "0123", ""},
+
+		{IntLit, "08123", "08123", "invalid digit '8' in octal literal"},
+		{IntLit, "01293", "01293", "invalid digit '9' in octal literal"},
+		{IntLit, "0F.", "0 F .", ""}, // only accept 0-9
+		{IntLit, "0123F.", "0123 F .", ""},
+		{IntLit, "0123456x", "0123456 x", ""},
+
+		// decimals
+		{IntLit, "1", "1", ""},
+		{IntLit, "1234", "1234", ""},
+
+		{IntLit, "1f", "1 f", ""}, // only accept 0-9
+
+		// decimal floats
+		{FloatLit, "0.", "0.", ""},
+		{FloatLit, "123.", "123.", ""},
+		{FloatLit, "0123.", "0123.", ""},
+
+		{FloatLit, ".0", ".0", ""},
+		{FloatLit, ".123", ".123", ""},
+		{FloatLit, ".0123", ".0123", ""},
+
+		{FloatLit, "0.0", "0.0", ""},
+		{FloatLit, "123.123", "123.123", ""},
+		{FloatLit, "0123.0123", "0123.0123", ""},
+
+		{FloatLit, "0e0", "0e0", ""},
+		{FloatLit, "123e+0", "123e+0", ""},
+		{FloatLit, "0123E-1", "0123E-1", ""},
+
+		{FloatLit, "0.e+1", "0.e+1", ""},
+		{FloatLit, "123.E-10", "123.E-10", ""},
+		{FloatLit, "0123.e123", "0123.e123", ""},
+
+		{FloatLit, ".0e-1", ".0e-1", ""},
+		{FloatLit, ".123E+10", ".123E+10", ""},
+		{FloatLit, ".0123E123", ".0123E123", ""},
+
+		{FloatLit, "0.0e1", "0.0e1", ""},
+		{FloatLit, "123.123E-10", "123.123E-10", ""},
+		{FloatLit, "0123.0123e+456", "0123.0123e+456", ""},
+
+		{FloatLit, "0e", "0e", "exponent has no digits"},
+		{FloatLit, "0E+", "0E+", "exponent has no digits"},
+		{FloatLit, "1e+f", "1e+ f", "exponent has no digits"},
+		{FloatLit, "0p0", "0p0", "'p' exponent requires hexadecimal mantissa"},
+		{FloatLit, "1.0P-1", "1.0P-1", "'P' exponent requires hexadecimal mantissa"},
+
+		// decimal imaginaries
+		{ImagLit, "0.i", "0.i", ""},
+		{ImagLit, ".123i", ".123i", ""},
+		{ImagLit, "123.123i", "123.123i", ""},
+		{ImagLit, "123e+0i", "123e+0i", ""},
+		{ImagLit, "123.E-10i", "123.E-10i", ""},
+		{ImagLit, ".123E+10i", ".123E+10i", ""},
+
+		// hexadecimals
+		{IntLit, "0x0", "0x0", ""},
+		{IntLit, "0x1234", "0x1234", ""},
+		{IntLit, "0xcafef00d", "0xcafef00d", ""},
+		{IntLit, "0XCAFEF00D", "0XCAFEF00D", ""},
+
+		{IntLit, "0x", "0x", "hexadecimal literal has no digits"},
+		{IntLit, "0x1g", "0x1 g", ""},
+
+		// hexadecimal floats
+		{FloatLit, "0x0p0", "0x0p0", ""},
+		{FloatLit, "0x12efp-123", "0x12efp-123", ""},
+		{FloatLit, "0xABCD.p+0", "0xABCD.p+0", ""},
+		{FloatLit, "0x.0189P-0", "0x.0189P-0", ""},
+		{FloatLit, "0x1.ffffp+1023", "0x1.ffffp+1023", ""},
+
+		{FloatLit, "0x.", "0x.", "hexadecimal literal has no digits"},
+		{FloatLit, "0x0.", "0x0.", "hexadecimal mantissa requires a 'p' exponent"},
+		{FloatLit, "0x.0", "0x.0", "hexadecimal mantissa requires a 'p' exponent"},
+		{FloatLit, "0x1.1", "0x1.1", "hexadecimal mantissa requires a 'p' exponent"},
+		{FloatLit, "0x1.1e0", "0x1.1e0", "hexadecimal mantissa requires a 'p' exponent"},
+		{FloatLit, "0x1.2gp1a", "0x1.2 gp1a", "hexadecimal mantissa requires a 'p' exponent"},
+		{FloatLit, "0x0p", "0x0p", "exponent has no digits"},
+		{FloatLit, "0xeP-", "0xeP-", "exponent has no digits"},
+		{FloatLit, "0x1234PAB", "0x1234P AB", "exponent has no digits"},
+		{FloatLit, "0x1.2p1a", "0x1.2p1 a", ""},
+
+		// hexadecimal imaginaries (invalid)
+		{ImagLit, "0xf00i", "0xf00i", "invalid suffix 'i' on hexadecimal literal"},
+		{ImagLit, "0xf00.bap+12i", "0xf00.bap+12i", "invalid suffix 'i' on hexadecimal literal"},
+
+		// separators
+		{IntLit, "0b_1000_0001", "0b_1000_0001", ""},
+		{IntLit, "0o_600", "0o_600", ""},
+		{IntLit, "0_466", "0_466", ""},
+		{IntLit, "1_000", "1_000", ""},
+		{FloatLit, "1_000.000_1", "1_000.000_1", ""},
+		{ImagLit, "10e+1_2_3i", "10e+1_2_3i", ""},
+		{IntLit, "0x_f00d", "0x_f00d", ""},
+		{FloatLit, "0x_f00d.0p1_2", "0x_f00d.0p1_2", ""},
+
+		{IntLit, "0b__1000", "0b__1000", "'_' must separate successive digits"},
+		{IntLit, "0o60___0", "0o60___0", "'_' must separate successive digits"},
+		{IntLit, "0466_", "0466_", "'_' must separate successive digits"},
+		{FloatLit, "1_.", "1_.", "'_' must separate successive digits"},
+		{FloatLit, "0._1", "0._1", "'_' must separate successive digits"},
+		{FloatLit, "2.7_e0", "2.7_e0", "'_' must separate successive digits"},
+		{ImagLit, "10e+12_i", "10e+12_i", "'_' must separate successive digits"},
+		{IntLit, "0x___0", "0x___0", "'_' must separate successive digits"},
+		{FloatLit, "0x1.0_p0", "0x1.0_p0", "'_' must separate successive digits"},
+	} {
+		var s scanner
+		var err string
+		s.init(strings.NewReader(test.src), func(_, _ uint, msg string) {
+			if err == "" {
+				err = msg
+			}
+		}, 0)
+
+		for i, want := range strings.Split(test.tokens, " ") {
+			err = ""
+			s.next()
+
+			// compute lit where where s.lit is not defined
+			var lit string
+			switch s.tok {
+			case _Name, _Literal:
+				lit = s.lit
+			case _Dot:
+				lit = "."
+			}
+
+			if i == 0 {
+				if s.tok != _Literal || s.kind != test.kind {
+					t.Errorf("%q: got token %s (kind = %d); want literal (kind = %d)", test.src, s.tok, s.kind, test.kind)
+				}
+				if err != test.err {
+					t.Errorf("%q: got error %q; want %q", test.src, err, test.err)
+				}
+			}
+
+			if lit != want {
+				t.Errorf("%q: got literal %q (%s); want %s", test.src, lit, s.tok, want)
+			}
+		}
+
+		// make sure we read all
+		s.next()
+		if s.tok == _Semi {
+			s.next()
+		}
+		if s.tok != _EOF {
+			t.Errorf("%q: got %s; want EOF", test.src, s.tok)
+		}
+	}
+}
+
 func TestScanErrors(t *testing.T) {
 	for _, test := range []struct {
 		src, msg  string
@@ -345,12 +551,10 @@ func TestScanErrors(t *testing.T) {
 
 		{"x + ~y", "invalid character U+007E '~'", 0, 4},
 		{"foo$bar = 0", "invalid character U+0024 '$'", 0, 3},
-		{"const x = 0xyz", "malformed hex constant", 0, 12},
+		{"0123456789", "invalid digit '8' in octal literal", 0, 8},
-		{"0123456789", "malformed octal constant", 0, 10},
 		{"0123456789. /* foobar", "comment not terminated", 0, 12},   // valid float constant
 		{"0123456789e0 /*\nfoobar", "comment not terminated", 0, 13}, // valid float constant
-		{"var a, b = 08, 07\n", "malformed octal constant", 0, 13},
+		{"var a, b = 09, 07\n", "invalid digit '9' in octal literal", 0, 12},
-		{"(x + 1.0e+x)", "malformed floating-point constant exponent", 0, 10},
 
 		{`''`, "empty character literal or unescaped ' in character literal", 0, 1},
 		{"'\n", "newline in character literal", 0, 1},

src/go/types/stdlib_test.go

@@ -155,6 +155,7 @@ func TestStdTest(t *testing.T) {
 	}
 
 	testTestDir(t, filepath.Join(runtime.GOROOT(), "test"),
+		"literal2.go",    // go/scanner cannot handle new number literals yet - TODO(gri) enable once fixed
 		"cmplxdivide.go", // also needs file cmplxdivide1.go - ignore
 	)
 }

test/fixedbugs/issue9036.go

@@ -4,7 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Expects to see error messages on 'p' exponents.
+// Expects to see error messages on 'p' exponents
+// for non-hexadecimal floats.
 
 package main
 
@@ -16,16 +17,9 @@ const (
 	x3 = 0x1e10 // integer (e is a hex digit)
 )
 
-// 'p' exponents are invalid - the 'p' is not considered
+const x4 = 0x1p10 // valid hexadecimal float
-// part of a floating-point number, but introduces a new
+const x5 = 1p10   // ERROR "'p' exponent requires hexadecimal mantissa"
-// (unexpected) name.
+const x6 = 0P0    // ERROR "'P' exponent requires hexadecimal mantissa"
-//
-// Error recovery is not ideal and we use a new declaration
-// each time for the parser to recover.
-
-const x4 = 0x1p10 // ERROR "unexpected p10"
-const x5 = 1p10   // ERROR "unexpected p10"
-const x6 = 0p0    // ERROR "unexpected p0"
 
 func main() {
 	fmt.Printf("%g %T\n", x1, x1)

test/literal2.go

@@ -0,0 +1,88 @@
+// run
+
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test Go2 literal syntax for basic types.
+// TODO add more tests
+
+package main
+
+import "fmt"
+
+func assert(cond bool) {
+	if !cond {
+		panic("assertion failed")
+	}
+}
+
+func equal(x, y float64) bool {
+	if x != y {
+		fmt.Printf("%g != %g\n", x, y)
+		return false
+	}
+	return true
+}
+
+func main() {
+	// 0-octals
+	assert(0_1 == 01)
+	assert(012 == 012)
+	assert(0_1_2 == 012)
+
+	// decimals
+	assert(1_000_000 == 1000000)
+
+	// hexadecimals
+	assert(0x_1 == 0x1)
+	assert(0x1_2 == 0x12)
+	assert(0X_cafe_f00d == 0xcafef00d)
+
+	// octals
+	assert(0o_1 == 01)
+	assert(0o12 == 012)
+	assert(0O_1_2 == 012)
+
+	// binaries
+	assert(0b_1 == 1)
+	assert(0b10 == 2)
+	assert(0b_1_0 == 2)
+
+	// decimal floats
+	assert(0. == 0.0)
+	assert(.0 == 0.0)
+	assert(1_0. == 10.0)
+	assert(.0_1 == 0.01)
+	assert(1_0.0_1 == 10.01)
+
+	assert(0.e1_0 == 0.0e10)
+	assert(.0e1_0 == 0.0e10)
+	assert(1_0.e1_0 == 10.0e10)
+	assert(.0_1e1_0 == 0.01e10)
+	assert(1_0.0_1e1_0 == 10.01e10)
+
+	// hexadecimal floats
+	assert(equal(0x1p-2, 0.25))
+	assert(equal(0x2.p10, 2048.0))
+	assert(equal(0x1.Fp+0, 1.9375))
+	assert(equal(0X.8p-0, 0.5))
+	assert(equal(0X1FFFP-16, 0.1249847412109375))
+	assert(equal(0x1.fffffffffffffp1023, 1.7976931348623157e308))
+
+	assert(equal(0x_1p-2, 0.25))
+	assert(equal(0x2.p1_0, 2048.0))
+	assert(equal(0x1_0.Fp+0, 16.9375))
+	assert(equal(0X_0.8p-0, 0.5))
+	assert(equal(0X_1FF_FP-16, 0.1249847412109375))
+	assert(equal(0x1.f_ffff_ffff_ffffP1_023, 1.7976931348623157e308))
+
+	// imaginaries
+	assert(0i == complex(0, 0))
+	assert(09i == complex(0, 9)) // "09i" is a decimal int followed by "i"
+	assert(1.2e+3i == complex(0, 1.2e+3))
+
+	assert(0_0i == complex(0, 0))
+	assert(0_9i == complex(0, 9)) // "0_9i" is a decimal int followed by "i"
+	assert(1.2_0e+0_3i == complex(0, 1.2e+3))
+}