Add syntax tests to augment the test coverage of

libsolidity/parsing/Scanner.cpp and libsolidity/parsing/Scanner.h
Fix #4627 and PR #5003.

- Add multiline comment test
- Add upper case hex literal test
- Add test for unicode escapes
- Add test for strings with escaped newlines
- Add test for string escapes
- Add test for strings that do not terminate before end of file
- Add test for unterminated blocks

test/libsolidity/syntaxTests/multiline_comments.sol

@@ -0,0 +1,13 @@
+/*
+ * This is a multi-line comment
+ * it should create no problems
+ *
+*/
+
+contract test {
+    /*
+    * this is another multi-line comment
+    *
+    */
+}
+// ----

test/libsolidity/syntaxTests/string/string_escapes.sol

@@ -0,0 +1,7 @@
+contract test {
+    function f() public pure returns (bytes32) {
+        bytes32 escapeCharacters = "\t\b\n\r\f\'\"\\\b";
+        return escapeCharacters;
+    }
+}
+// ----

test/libsolidity/syntaxTests/string/string_new_line.sol

@@ -0,0 +1,9 @@
+contract test {
+    function f() public pure returns (bytes32) {
+        bytes32 escapeCharacters = "This a test
+        ";
+        return escapeCharacters;
+    }
+}
+// ----
+// ParserError: (100-112): Expected primary expression.

test/libsolidity/syntaxTests/string/string_terminated_by_backslash.sol

@@ -0,0 +1,8 @@
+contract test {
+    function f() public pure returns (bytes32) {
+        bytes32 escapeCharacters = "text \";
+        return escapeCharacters;
+    }
+}
+// ----
+// ParserError: (100-109): Expected primary expression.

test/libsolidity/syntaxTests/string/string_unterminated.sol

@@ -0,0 +1,7 @@
+contract test {
+    function f() public pure returns (bytes32) {
+        bytes32 escapeCharacters = "This a test
+    }
+}
+// ----
+// ParserError: (100-112): Expected primary expression.

test/libsolidity/syntaxTests/string/string_unterminated_no_new_line.sol

@@ -0,0 +1,4 @@
+contract test {
+    function f() pure public { "abc\
+// ----
+// ParserError: (47-53): Expected primary expression.

test/libsolidity/syntaxTests/unicode_escape_literals.sol

@@ -0,0 +1,31 @@
+contract test {
+
+    function oneByteUTF8() public pure returns (bytes32) {
+        bytes32 usdollar = "aaa\u0024aaa";
+        return usdollar;
+    }
+
+    function twoBytesUTF8() public pure returns (bytes32) {
+        bytes32 cent = "aaa\u00A2aaa";
+        return cent;
+    }
+
+    function threeBytesUTF8() public pure returns (bytes32) {
+        bytes32 eur = "aaa\u20ACaaa";
+        return  eur;
+    }
+
+    function together() public pure returns (bytes32) {
+        bytes32 res = "\u0024\u00A2\u20AC";
+        return res;
+    }
+
+    // this function returns an invalid unicode character
+    function invalidLiteral() public pure returns(bytes32) {
+        bytes32 invalid = "\u00xx";
+        return invalid;
+    }
+
+}
+// ----
+// ParserError: (678-681): Expected primary expression.

test/libsolidity/syntaxTests/unterminatedBlocks/one_dot.sol

@@ -0,0 +1,4 @@
+contract c {
+    function f() pure public { 1.
+// ----
+// ParserError: (47-47): Expected identifier but got end of source

test/libsolidity/syntaxTests/unterminatedBlocks/one_dot_x.sol

@@ -0,0 +1,5 @@
+contract test {
+    function f() pure public { 1.x; }
+}
+// ----
+// TypeError: (47-50): Member "x" not found or not visible after argument-dependent lookup in int_const 1.

test/libsolidity/syntaxTests/unterminatedBlocks/zero_dot.sol

@@ -0,0 +1,4 @@
+contract c {
+    function f() pure public { 0.
+// ----
+// ParserError: (47-47): Expected identifier but got end of source

test/libsolidity/syntaxTests/unterminatedBlocks/zero_dot_x.sol

@@ -0,0 +1,5 @@
+contract test {
+    function f() pure public { 0.x; }
+}
+// ----
+// TypeError: (47-50): Member "x" not found or not visible after argument-dependent lookup in int_const 0.

test/libsolidity/syntaxTests/upper_case_hex_literals.sol

@@ -0,0 +1,9 @@
+contract test {
+
+    function f() public pure returns (uint256) {
+        uint256 a = 0x1234aAbcC;
+        uint256 b = 0x1234ABCDEF;
+        return a + b;
+    }
+}
+// ----