StandardCompiler: Don't assume that link reference always contains a colon

libsolidity/interface/StandardCompiler.cpp

@@ -323,10 +323,12 @@ Json::Value formatLinkReferences(std::map<size_t, std::string> const& linkRefere
 	for (auto const& ref: linkReferences)
 	{
 		string const& fullname = ref.second;
+
+		// If the link reference does not contain a colon, assume that the file name is missing and
+		// the whole string represents the library name.
 		size_t colon = fullname.rfind(':');
-		solAssert(colon != string::npos, "");
+		string file = (colon != string::npos ? fullname.substr(0, colon) : "");
-		string file = fullname.substr(0, colon);
+		string name = (colon != string::npos ? fullname.substr(colon + 1) : fullname);
-		string name = fullname.substr(colon + 1);
 
 		Json::Value fileObject = ret.get(file, Json::objectValue);
 		Json::Value libraryArray = fileObject.get(name, Json::arrayValue);

test/cmdlineTests/linking_strict_assembly_no_file_name_in_link_reference/args

@@ -0,0 +1 @@
+--strict-assembly --libraries L:0x1234567890123456789012345678901234567890

test/cmdlineTests/linking_strict_assembly_no_file_name_in_link_reference/err

@@ -0,0 +1 @@
+Warning: Yul is still experimental. Please use the output with care.

test/cmdlineTests/linking_strict_assembly_no_file_name_in_link_reference/input.yul

@@ -0,0 +1,5 @@
+object "a" {
+    code {
+        let addr := linkersymbol("L")
+    }
+}

test/cmdlineTests/linking_strict_assembly_no_file_name_in_link_reference/output

@@ -0,0 +1,16 @@
+
+======= linking_strict_assembly_no_file_name_in_link_reference/input.yul (EVM) =======
+
+Pretty printed source:
+object "a" {
+    code { let addr := linkersymbol("L") }
+}
+
+
+Binary representation:
+73123456789012345678901234567890123456789050
+
+Text representation:
+  linkerSymbol("8aa64f937099b65a4febc243a5ae0f2d6416bb9e473c30dd29c1ee498fb7c5a8")
+    /* "linking_strict_assembly_no_file_name_in_link_reference/input.yul":22:67   */
+  pop

test/libsolidity/StandardCompiler.cpp

@@ -903,6 +903,70 @@ BOOST_AUTO_TEST_CASE(library_linking)
 	expectLinkReferences(contractResult, {{"library2.sol", {"L2"}}});
 }
 
+BOOST_AUTO_TEST_CASE(linking_yul_empty_link_reference)
+{
+	char const* input = R"(
+	{
+		"language": "Yul",
+		"settings": {
+			"libraries": {
+				"": {
+					"": "0x4200000000000000000000000000000000000001"
+				}
+			},
+			"outputSelection": {
+				"fileA": {
+					"*": [
+						"evm.bytecode.linkReferences"
+					]
+				}
+			}
+		},
+		"sources": {
+			"fileA": {
+				"content": "object \"a\" { code { let addr := linkersymbol(\"\") } }"
+			}
+		}
+	}
+	)";
+	Json::Value result = compile(input);
+	BOOST_TEST(containsAtMostWarnings(result));
+	Json::Value contractResult = getContractResult(result, "fileA", "a");
+	expectLinkReferences(contractResult, {});
+}
+
+BOOST_AUTO_TEST_CASE(linking_yul_no_filename_in_link_reference)
+{
+	char const* input = R"(
+	{
+		"language": "Yul",
+		"settings": {
+			"libraries": {
+				"": {
+					"L": "0x4200000000000000000000000000000000000001"
+				}
+			},
+			"outputSelection": {
+				"fileA": {
+					"*": [
+						"evm.bytecode.linkReferences"
+					]
+				}
+			}
+		},
+		"sources": {
+			"fileA": {
+				"content": "object \"a\" { code { let addr := linkersymbol(\"L\") } }"
+			}
+		}
+	}
+	)";
+	Json::Value result = compile(input);
+	BOOST_TEST(containsAtMostWarnings(result));
+	Json::Value contractResult = getContractResult(result, "fileA", "a");
+	expectLinkReferences(contractResult, {});
+}
+
 BOOST_AUTO_TEST_CASE(evm_version)
 {
 	auto inputForVersion = [](string const& _version)