Make external library functions accessible.

test/libsolidity/SolidityEndToEndTest.cpp

@@ -6955,6 +6955,21 @@ BOOST_AUTO_TEST_CASE(library_call)
 	ABI_CHECK(callContractFunction("f(uint256)", u256(33)), encodeArgs(u256(33) * 9));
 }
 
+BOOST_AUTO_TEST_CASE(library_function_external)
+{
+	char const* sourceCode = R"(
+		library Lib { function m(bytes b) external pure returns (byte) { return b[2]; } }
+		contract Test {
+			function f(bytes b) public pure returns (byte) {
+				return Lib.m(b);
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 0, "Lib");
+	compileAndRun(sourceCode, 0, "Test", bytes(), map<string, Address>{{"Lib", m_contractAddress}});
+	ABI_CHECK(callContractFunction("f(bytes)", u256(0x20), u256(5), "abcde"), encodeArgs("c"));
+}
+
 BOOST_AUTO_TEST_CASE(library_stray_values)
 {
 	char const* sourceCode = R"(

test/libsolidity/syntaxTests/visibility/external_library_function.sol

@@ -0,0 +1,14 @@
+library L {
+    function f(uint) pure external {}
+}
+
+contract C {
+    using L for *;
+
+    function f() public pure {
+        L.f(2);
+        uint x;
+        x.f();
+    }
+}
+// ----