Allow hex string literals in Yul.

test/libsolidity/syntaxTests/inlineAssembly/hex_assignment.sol

@@ -6,4 +6,3 @@ contract C {
   }
 }
 // ----
-// ParserError 3772: (72-81): Hex literals are not valid in this context.

test/libsolidity/syntaxTests/inlineAssembly/hex_expression.sol

@@ -6,4 +6,3 @@ contract C {
   }
 }
 // ----
-// ParserError 3772: (67-76): Hex literals are not valid in this context.

test/libsolidity/syntaxTests/inlineAssembly/hex_switch_case.sol

@@ -8,4 +8,3 @@ contract C {
   }
 }
 // ----
-// ParserError 3772: (92-99): Hex literals are not valid in this context.

test/libsolidity/syntaxTests/literals/hex_string_duplicate_underscore_yul.sol

@@ -0,0 +1,9 @@
+contract C {
+    function f() public pure {
+        assembly {
+            let x := hex"12__34";
+        }
+    }
+}
+// ----
+// ParserError 1465: (84-92): Illegal token: Invalid use of number separator '_'.

test/libsolidity/syntaxTests/literals/hex_string_invalid_characters_yul.sol

@@ -0,0 +1,9 @@
+contract C {
+    function f() public pure {
+        assembly {
+            let x := hex"abxy";
+        }
+    }
+}
+// ----
+// ParserError 1465: (84-90): Illegal token: Expected even number of hex-nibbles.

test/libsolidity/syntaxTests/string/hex_as_identifier.sol

@@ -0,0 +1,5 @@
+function g() pure {
+    assembly { let hex := 1 }
+}
+// ----
+// ParserError 2314: (39-42): Expected identifier but got 'ILLEGAL'

test/libyul/yulInterpreterTests/hex_literals.yul

@@ -0,0 +1,12 @@
+{
+	let x := hex"112233445566778899aabbccddeeff6677889900"
+	let y := hex"1234_abcd"
+	sstore(0, x)
+	sstore(1, y)
+}
+// ----
+// Trace:
+// Memory dump:
+// Storage dump:
+//   0000000000000000000000000000000000000000000000000000000000000000: 112233445566778899aabbccddeeff6677889900000000000000000000000000
+//   0000000000000000000000000000000000000000000000000000000000000001: 1234abcd00000000000000000000000000000000000000000000000000000000

test/libyul/yulSyntaxTests/hex_assignment.yul

@@ -2,4 +2,3 @@
     let x := hex"0011"
 }
 // ----
-// ParserError 3772: (15-24): Hex literals are not valid in this context.

test/libyul/yulSyntaxTests/hex_assignment_long.yul

@@ -0,0 +1,5 @@
+{
+    let x := hex"00110011001100110011001100110011001100110011001100110011001100110011001100110011"
+}
+// ----
+// TypeError 3069: (15-100): String literal too long (40 > 32)

test/libyul/yulSyntaxTests/hex_expression.yul

@@ -2,4 +2,3 @@
     pop(hex"2233")
 }
 // ----
-// ParserError 3772: (10-19): Hex literals are not valid in this context.

test/libyul/yulSyntaxTests/hex_string_literal_odd.yul

@@ -0,0 +1,7 @@
+{
+    let name := hex"abc"
+}
+// ====
+// dialect: evm
+// ----
+// ParserError 1465: (18-24): Illegal token: Expected even number of hex-nibbles.

test/libyul/yulSyntaxTests/hex_switch_case.yul

@@ -4,4 +4,3 @@
     case hex"1122" {}
 }
 // ----
-// ParserError 3772: (33-40): Hex literals are not valid in this context.

test/libyul/yulSyntaxTests/hex_switch_case_long.yul

@@ -0,0 +1,7 @@
+{
+    switch codesize()
+    case hex"00" {}
+    case hex"112233445566778899001122334455667788990011223344556677889900112233445566778899001122334455667788990011223344556677889900" {}
+}
+// ----
+// TypeError 3069: (53-178): String literal too long (60 > 32)