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>

1 files changed, 88 insertions, 0 deletions

diff --git a/test/literal2.go b/test/literal2.go
new file mode 100644
index 0000000000..dbe22a012e
--- /dev/null
+++ b/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))
+}