go/scanner: accept 'i' suffix orthogonally on all numbers

This change accepts the 'i' suffix on binary and octal integer
literals as well as hexadecimal floats. The suffix was already
accepted on decimal integers and floats.

See also the respective language in the spec change:
https://golang.org/cl/161098

Change-Id: I0c182bdf58f8fd1f70090e581b3ccb2f5e2e4e79
Reviewed-on: https://go-review.googlesource.com/c/162880Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/go/scanner/scanner.go

@@ -472,9 +472,6 @@ func (s *Scanner) scanNumber() (token.Token, string) {
 	// suffix 'i'
 	if s.ch == 'i' {
 		tok = token.IMAG
-		if prefix != 0 && prefix != '0' {
-			s.error(s.offset, "invalid suffix 'i' on "+litname(prefix))
-		}
 		s.next()
 	}
 

src/go/scanner/scanner_test.go

@@ -927,13 +927,14 @@ func TestNumbers(t *testing.T) {
 		{token.INT, "0b0190", "0b0190", "invalid digit '9' in binary literal"},
 		{token.INT, "0b01a0", "0b01 a0", ""}, // only accept 0-9
 
-		// binary floats and imaginaries (invalid)
 		{token.FLOAT, "0b.", "0b.", "invalid radix point in binary literal"},
 		{token.FLOAT, "0b.1", "0b.1", "invalid radix point in binary literal"},
 		{token.FLOAT, "0b1.0", "0b1.0", "invalid radix point in binary literal"},
 		{token.FLOAT, "0b1e10", "0b1e10", "'e' exponent requires decimal mantissa"},
 		{token.FLOAT, "0b1P-1", "0b1P-1", "'P' exponent requires hexadecimal mantissa"},
-		{token.IMAG, "0b10i", "0b10i", "invalid suffix 'i' on binary literal"},
+
+		{token.IMAG, "0b10i", "0b10i", ""},
+		{token.IMAG, "0b10.0i", "0b10.0i", "invalid radix point in binary literal"},
 
 		// octals
 		{token.INT, "0o0", "0o0", ""},
@@ -945,13 +946,14 @@ func TestNumbers(t *testing.T) {
 		{token.INT, "0o1293", "0o1293", "invalid digit '9' in octal literal"},
 		{token.INT, "0o12a3", "0o12 a3", ""}, // only accept 0-9
 
-		// octal floats and imaginaries (invalid)
 		{token.FLOAT, "0o.", "0o.", "invalid radix point in octal literal"},
 		{token.FLOAT, "0o.2", "0o.2", "invalid radix point in octal literal"},
 		{token.FLOAT, "0o1.2", "0o1.2", "invalid radix point in octal literal"},
 		{token.FLOAT, "0o1E+2", "0o1E+2", "'E' exponent requires decimal mantissa"},
 		{token.FLOAT, "0o1p10", "0o1p10", "'p' exponent requires hexadecimal mantissa"},
-		{token.IMAG, "0o10i", "0o10i", "invalid suffix 'i' on octal literal"},
+
+		{token.IMAG, "0o10i", "0o10i", ""},
+		{token.IMAG, "0o10e0i", "0o10e0i", "'e' exponent requires decimal mantissa"},
 
 		// 0-octals
 		{token.INT, "0", "0", ""},
@@ -969,6 +971,9 @@ func TestNumbers(t *testing.T) {
 
 		{token.INT, "1f", "1 f", ""}, // only accept 0-9
 
+		{token.IMAG, "0i", "0i", ""},
+		{token.IMAG, "0678i", "0678i", ""},
+
 		// decimal floats
 		{token.FLOAT, "0.", "0.", ""},
 		{token.FLOAT, "123.", "123.", ""},
@@ -1004,7 +1009,6 @@ func TestNumbers(t *testing.T) {
 		{token.FLOAT, "0p0", "0p0", "'p' exponent requires hexadecimal mantissa"},
 		{token.FLOAT, "1.0P-1", "1.0P-1", "'P' exponent requires hexadecimal mantissa"},
 
-		// decimal imaginaries
 		{token.IMAG, "0.i", "0.i", ""},
 		{token.IMAG, ".123i", ".123i", ""},
 		{token.IMAG, "123.123i", "123.123i", ""},
@@ -1021,6 +1025,8 @@ func TestNumbers(t *testing.T) {
 		{token.INT, "0x", "0x", "hexadecimal literal has no digits"},
 		{token.INT, "0x1g", "0x1 g", ""},
 
+		{token.IMAG, "0xf00i", "0xf00i", ""},
+
 		// hexadecimal floats
 		{token.FLOAT, "0x0p0", "0x0p0", ""},
 		{token.FLOAT, "0x12efp-123", "0x12efp-123", ""},
@@ -1039,9 +1045,7 @@ func TestNumbers(t *testing.T) {
 		{token.FLOAT, "0x1234PAB", "0x1234P AB", "exponent has no digits"},
 		{token.FLOAT, "0x1.2p1a", "0x1.2p1 a", ""},
 
-		// hexadecimal imaginaries (invalid)
-		{token.IMAG, "0xf00i", "0xf00i", "invalid suffix 'i' on hexadecimal literal"},
-		{token.IMAG, "0xf00.bap+12i", "0xf00.bap+12i", "invalid suffix 'i' on hexadecimal literal"},
+		{token.IMAG, "0xf00.bap+12i", "0xf00.bap+12i", ""},
 
 		// separators
 		{token.INT, "0b_1000_0001", "0b_1000_0001", ""},