cmd/compile: 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.

Note that 0123i == 123i for backward-compatibility (and 09i is
valid).

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

Change-Id: I9d2d755cba36a3fa7b9e24308c73754d4568daaf
Reviewed-on: https://go-review.googlesource.com/c/162878
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

3 files changed, 15 insertions, 11 deletions

diff --git a/src/cmd/compile/internal/syntax/scanner.go b/src/cmd/compile/internal/syntax/scanner.go
index 0a77d48b3d..fbb3e1a40e 100644
--- a/src/cmd/compile/internal/syntax/scanner.go
+++ b/src/cmd/compile/internal/syntax/scanner.go
@@ -512,9 +512,6 @@ func (s *scanner) number(c rune) {
 	// suffix 'i'
 	if c == 'i' {
 		s.kind = ImagLit
-		if prefix != 0 && prefix != '0' {
-			s.error("invalid suffix 'i' on " + litname(prefix))
-		}
 		c = s.getr()
 	}
 	s.ungetr()
diff --git a/src/cmd/compile/internal/syntax/scanner_test.go b/src/cmd/compile/internal/syntax/scanner_test.go
index 0f0579e2a5..bfc44950be 100644
--- a/src/cmd/compile/internal/syntax/scanner_test.go
+++ b/src/cmd/compile/internal/syntax/scanner_test.go
@@ -347,13 +347,14 @@ func TestNumbers(t *testing.T) {
 		{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"},
+
+		{ImagLit, "0b10i", "0b10i", ""},
+		{ImagLit, "0b10.0i", "0b10.0i", "invalid radix point in binary literal"},
 
 		// octals
 		{IntLit, "0o0", "0o0", ""},
@@ -365,13 +366,14 @@ func TestNumbers(t *testing.T) {
 		{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"},
+
+		{ImagLit, "0o10i", "0o10i", ""},
+		{ImagLit, "0o10e0i", "0o10e0i", "'e' exponent requires decimal mantissa"},
 
 		// 0-octals
 		{IntLit, "0", "0", ""},
@@ -389,6 +391,9 @@ func TestNumbers(t *testing.T) {
 
 		{IntLit, "1f", "1 f", ""}, // only accept 0-9
 
+		{ImagLit, "0i", "0i", ""},
+		{ImagLit, "0678i", "0678i", ""},
+
 		// decimal floats
 		{FloatLit, "0.", "0.", ""},
 		{FloatLit, "123.", "123.", ""},
@@ -424,7 +429,6 @@ func TestNumbers(t *testing.T) {
 		{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", ""},
@@ -441,6 +445,8 @@ func TestNumbers(t *testing.T) {
 		{IntLit, "0x", "0x", "hexadecimal literal has no digits"},
 		{IntLit, "0x1g", "0x1 g", ""},
 
+		{ImagLit, "0xf00i", "0xf00i", ""},
+
 		// hexadecimal floats
 		{FloatLit, "0x0p0", "0x0p0", ""},
 		{FloatLit, "0x12efp-123", "0x12efp-123", ""},
@@ -459,9 +465,7 @@ func TestNumbers(t *testing.T) {
 		{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"},
+		{ImagLit, "0xf00.bap+12i", "0xf00.bap+12i", ""},
 
 		// separators
 		{IntLit, "0b_1000_0001", "0b_1000_0001", ""},
diff --git a/src/cmd/compile/internal/syntax/tokens.go b/src/cmd/compile/internal/syntax/tokens.go
index e00255a45e..9b26c9f12f 100644
--- a/src/cmd/compile/internal/syntax/tokens.go
+++ b/src/cmd/compile/internal/syntax/tokens.go
@@ -92,6 +92,9 @@ func contains(tokset uint64, tok token) bool {
 
 type LitKind uint
 
+// TODO(gri) With the 'i' (imaginary) suffix now permitted on integer
+//           and floating-point numbers, having a single ImagLit does
+//           not represent the literal kind well anymore. Remove it?
 const (
 	IntLit LitKind = iota
 	FloatLit