Constants at file-level.

test/libsolidity/semanticTests/constants/constant_string_at_file_level.sol

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+bytes constant a = "\x03\x01\x02";
+bytes constant b = hex"030102";
+string constant c = "hello";
+uint256 constant x = 56;
+enum ActionChoices {GoLeft, GoRight, GoStraight, Sit}
+ActionChoices constant choices = ActionChoices.GoLeft;
+bytes32 constant st = "abc\x00\xff__";
+
+contract C {
+    function f() public returns (bytes memory) {
+        return a;
+    }
+
+    function g() public returns (bytes memory) {
+        return b;
+    }
+
+    function h() public returns (bytes memory) {
+        return bytes(c);
+    }
+
+    function i() public returns (uint, ActionChoices, bytes32) {
+        return (x, choices, st);
+    }
+}
+
+// ====
+// compileViaYul: also
+// ----
+// f() -> 0x20, 3, "\x03\x01\x02"
+// g() -> 0x20, 3, "\x03\x01\x02"
+// h() -> 0x20, 5, "hello"