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>

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

@@ -183,16 +183,34 @@ 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
 
+	// TODO(gri) why is this needed?
 	for len(as) > 0 && (as[0] == ' ' || as[0] == '\t') {
 		as = as[1:]
 	}
 
-	f, _, err := a.Val.Parse(as, 0)
+	// Currently, Val.Parse below (== math/big.Float.Parse) does not
+	// handle the 0o-octal prefix which can appear with octal integers
+	// with 'i' suffix, which end up here as imaginary components of
+	// complex numbers. Handle explicitly for now.
+	// TODO(gri) remove once Float.Parse can handle octals (it handles 0b/0B)
+	var f *big.Float
+	if strings.HasPrefix(as, "0o") || strings.HasPrefix(as, "0O") {
+		x, ok := new(big.Int).SetString(as[2:], 8)
+		if !ok {
+			yyerror("malformed constant: %s", as)
+			a.Val.SetFloat64(0)
+			return
+		}
+		f = a.Val.SetInt(x)
+	} else {
+		var err error
+		f, _, err = a.Val.Parse(as, 0)
 		if err != nil {
 			yyerror("malformed constant: %s (%v)", as, err)
 			a.Val.SetFloat64(0)
 			return
 		}
+	}
 
 	if f.IsInf() {
 		yyerror("constant too large: %s", as)

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()

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", ""},

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

test/literal2.go

@@ -5,7 +5,8 @@
 // license that can be found in the LICENSE file.
 
 // Test Go2 literal syntax for basic types.
-// TODO add more tests
+// Avoid running gofmt on this file to preserve the
+// test cases with upper-case prefixes (0B, 0O, 0X).
 
 package main
 
@@ -17,7 +18,7 @@ func assert(cond bool) {
 	}
 }
 
-func equal(x, y float64) bool {
+func equal(x, y interface{}) bool {
 	if x != y {
 		fmt.Printf("%g != %g\n", x, y)
 		return false
@@ -30,24 +31,30 @@ func main() {
 	assert(0_1 == 01)
 	assert(012 == 012)
 	assert(0_1_2 == 012)
+	assert(0_1_2i == complex(0, 12)) // decimal digits despite leading 0 for backward-compatibility
+	assert(00089i == complex(0, 89)) // decimal digits despite leading 0 for backward-compatibility
 
 	// decimals
 	assert(1_000_000 == 1000000)
+	assert(1_000i == complex(0, 1000))
 
 	// hexadecimals
 	assert(0x_1 == 0x1)
 	assert(0x1_2 == 0x12)
-	assert(0X_cafe_f00d == 0xcafef00d)
+	assert(0x_cafe_f00d == 0xcafef00d)
+	assert(0x_cafei == complex(0, 0xcafe))
 
 	// octals
 	assert(0o_1 == 01)
 	assert(0o12 == 012)
-	assert(0O_1_2 == 012)
+	assert(0o_1_2 == 012)
+	assert(0o_1_2i == complex(0, 0o12))
 
 	// binaries
 	assert(0b_1 == 1)
 	assert(0b10 == 2)
 	assert(0b_1_0 == 2)
+	assert(0b_1_0i == complex(0, 2))
 
 	// decimal floats
 	assert(0. == 0.0)
@@ -55,34 +62,29 @@ func main() {
 	assert(1_0. == 10.0)
 	assert(.0_1 == 0.01)
 	assert(1_0.0_1 == 10.01)
+	assert(1_0.0_1i == complex(0, 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)
+	assert(1_0.0_1e1_0i == complex(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(0x.8p-0, 0.5))
+	assert(equal(0x1FFFp-16, 0.1249847412109375))
 	assert(equal(0x1.fffffffffffffp1023, 1.7976931348623157e308))
+	assert(equal(0x1.fffffffffffffp1023i, complex(0, 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))
+	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))
+	assert(equal(0x1.f_ffff_ffff_ffffp1_023i, complex(0, 1.7976931348623157e308)))
 }