runtime(java): Improve the recognition of literals (#14120)

* Emend the Unicode and octal escape sequence patterns;
* Accept the (repeated) underscore separators in all
  numerical literals;
* Recognise hexadecimal floating-point literals.

(The space escape sequence '\s' will be introduced along
with text blocks in another PR.)

References:
https://docs.oracle.com/javase/specs/jls/se17/html/jls-3.html#jls-3.3
https://docs.oracle.com/javase/specs/jls/se17/html/jls-3.html#jls-3.10.1
https://docs.oracle.com/javase/specs/jls/se17/html/jls-3.html#jls-3.10.2
https://docs.oracle.com/javase/specs/jls/se17/html/jls-3.html#jls-3.10.7


Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

1 files changed, 123 insertions, 0 deletions

diff --git a/runtime/syntax/testdir/input/java_escapes.java b/runtime/syntax/testdir/input/java_escapes.java
new file mode 100644
index 0000000000..624d4fcd89
--- /dev/null
+++ b/runtime/syntax/testdir/input/java_escapes.java
@@ -0,0 +1,123 @@
+class EscapesTests
+{	// javap -constants EscapesTests.class
+	// static final String hello = "hello";
+	\u0073\u0074\u0061\u0074\u0069\u0063
+	\u0066\u0069\u006e\u0061\u006c
+	\u0053\u0074\u0072\u0069\u006e\u0067
+	\u0068\u0065\u006c\u006c\u006f
+	\u003d
+	\u0022\u0068\u0065\u006c\u006c\u006f\u0022
+	\u003b
+
+	static {
+		char ee[] = {
+			'\b', '\t',
+			'\n', '\f', '\r',
+			'\"', '\'', '\\',
+		};
+
+		System.out.println(new String[] {
+			"\b", "\t",
+			"\n", "\f", "\r",
+			"\"", "\'", "\\",
+		});
+
+		char oo[] = {
+			'\0', '\1', '\2', '\3', '\4', '\5', '\6', '\7',
+
+		'\00', '\01', '\02', '\03', '\04', '\05', '\06', '\07',
+
+	'\000', '\001', '\002', '\003', '\004', '\005', '\006', '\007',
+
+		'\10', '\11', '\12', '\13', '\14', '\15', '\16', '\17',
+		'\20', '\21', '\22', '\23', '\24', '\25', '\26', '\27',
+		'\30', '\31', '\32', '\33', '\34', '\35', '\36', '\37',
+		'\40', '\41', '\42', '\43', '\44', '\45', '\46', '\47',
+		'\50', '\51', '\52', '\53', '\54', '\55', '\56', '\57',
+		'\60', '\61', '\62', '\63', '\64', '\65', '\66', '\67',
+		'\70', '\71', '\72', '\73', '\74', '\75', '\76', '\77',
+
+	'\010', '\011', '\012', '\013', '\014', '\015', '\016', '\017',
+	'\020', '\021', '\022', '\023', '\024', '\025', '\026', '\027',
+	'\030', '\031', '\032', '\033', '\034', '\035', '\036', '\037',
+	'\040', '\041', '\042', '\043', '\044', '\045', '\046', '\047',
+	'\050', '\051', '\052', '\053', '\054', '\055', '\056', '\057',
+	'\060', '\061', '\062', '\063', '\064', '\065', '\066', '\067',
+	'\070', '\071', '\072', '\073', '\074', '\075', '\076', '\077',
+
+	'\100', '\101', '\102', '\103', '\104', '\105', '\106', '\107',
+	'\110', '\111', '\112', '\113', '\114', '\115', '\116', '\117',
+	'\120', '\121', '\122', '\123', '\124', '\125', '\126', '\127',
+	'\130', '\131', '\132', '\133', '\134', '\135', '\136', '\137',
+	'\140', '\141', '\142', '\143', '\144', '\145', '\146', '\147',
+	'\150', '\151', '\152', '\153', '\154', '\155', '\156', '\157',
+	'\160', '\161', '\162', '\163', '\164', '\165', '\166', '\167',
+	'\170', '\171', '\172', '\173', '\174', '\175', '\176', '\177',
+	'\200', '\201', '\202', '\203', '\204', '\205', '\206', '\207',
+	'\210', '\211', '\212', '\213', '\214', '\215', '\216', '\217',
+	'\220', '\221', '\222', '\223', '\224', '\225', '\226', '\227',
+	'\230', '\231', '\232', '\233', '\234', '\235', '\236', '\237',
+	'\240', '\241', '\242', '\243', '\244', '\245', '\246', '\247',
+	'\250', '\251', '\252', '\253', '\254', '\255', '\256', '\257',
+	'\260', '\261', '\262', '\263', '\264', '\265', '\266', '\267',
+	'\270', '\271', '\272', '\273', '\274', '\275', '\276', '\277',
+	'\300', '\301', '\302', '\303', '\304', '\305', '\306', '\307',
+	'\310', '\311', '\312', '\313', '\314', '\315', '\316', '\317',
+	'\320', '\321', '\322', '\323', '\324', '\325', '\326', '\327',
+	'\330', '\331', '\332', '\333', '\334', '\335', '\336', '\337',
+	'\340', '\341', '\342', '\343', '\344', '\345', '\346', '\347',
+	'\350', '\351', '\352', '\353', '\354', '\355', '\356', '\357',
+	'\360', '\361', '\362', '\363', '\364', '\365', '\366', '\367',
+	'\370', '\371', '\372', '\373', '\374', '\375', '\376', '\377',
+		};
+
+		System.out.println(new String[] {
+			"\0", "\1", "\2", "\3", "\4", "\5", "\6", "\7",
+
+		"\00", "\01", "\02", "\03", "\04", "\05", "\06", "\07",
+
+	"\000", "\001", "\002", "\003", "\004", "\005", "\006", "\007",
+
+		"\10", "\11", "\12", "\13", "\14", "\15", "\16", "\17",
+		"\20", "\21", "\22", "\23", "\24", "\25", "\26", "\27",
+		"\30", "\31", "\32", "\33", "\34", "\35", "\36", "\37",
+		"\40", "\41", "\42", "\43", "\44", "\45", "\46", "\47",
+		"\50", "\51", "\52", "\53", "\54", "\55", "\56", "\57",
+		"\60", "\61", "\62", "\63", "\64", "\65", "\66", "\67",
+		"\70", "\71", "\72", "\73", "\74", "\75", "\76", "\77",
+
+	"\010", "\011", "\012", "\013", "\014", "\015", "\016", "\017",
+	"\020", "\021", "\022", "\023", "\024", "\025", "\026", "\027",
+	"\030", "\031", "\032", "\033", "\034", "\035", "\036", "\037",
+	"\040", "\041", "\042", "\043", "\044", "\045", "\046", "\047",
+	"\050", "\051", "\052", "\053", "\054", "\055", "\056", "\057",
+	"\060", "\061", "\062", "\063", "\064", "\065", "\066", "\067",
+	"\070", "\071", "\072", "\073", "\074", "\075", "\076", "\077",
+
+	"\100", "\101", "\102", "\103", "\104", "\105", "\106", "\107",
+	"\110", "\111", "\112", "\113", "\114", "\115", "\116", "\117",
+	"\120", "\121", "\122", "\123", "\124", "\125", "\126", "\127",
+	"\130", "\131", "\132", "\133", "\134", "\135", "\136", "\137",
+	"\140", "\141", "\142", "\143", "\144", "\145", "\146", "\147",
+	"\150", "\151", "\152", "\153", "\154", "\155", "\156", "\157",
+	"\160", "\161", "\162", "\163", "\164", "\165", "\166", "\167",
+	"\170", "\171", "\172", "\173", "\174", "\175", "\176", "\177",
+	"\200", "\201", "\202", "\203", "\204", "\205", "\206", "\207",
+	"\210", "\211", "\212", "\213", "\214", "\215", "\216", "\217",
+	"\220", "\221", "\222", "\223", "\224", "\225", "\226", "\227",
+	"\230", "\231", "\232", "\233", "\234", "\235", "\236", "\237",
+	"\240", "\241", "\242", "\243", "\244", "\245", "\246", "\247",
+	"\250", "\251", "\252", "\253", "\254", "\255", "\256", "\257",
+	"\260", "\261", "\262", "\263", "\264", "\265", "\266", "\267",
+	"\270", "\271", "\272", "\273", "\274", "\275", "\276", "\277",
+	"\300", "\301", "\302", "\303", "\304", "\305", "\306", "\307",
+	"\310", "\311", "\312", "\313", "\314", "\315", "\316", "\317",
+	"\320", "\321", "\322", "\323", "\324", "\325", "\326", "\327",
+	"\330", "\331", "\332", "\333", "\334", "\335", "\336", "\337",
+	"\340", "\341", "\342", "\343", "\344", "\345", "\346", "\347",
+	"\350", "\351", "\352", "\353", "\354", "\355", "\356", "\357",
+	"\360", "\361", "\362", "\363", "\364", "\365", "\366", "\367",
+	"\370", "\371", "\372", "\373", "\374", "\375", "\376", "\377",
+		});
+	}
+}