fix: check for main.swift when finding identifying binary targets

examples/vapor_example/Sources/Run/BUILD.bazel

@@ -1,6 +1,6 @@
-load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
+load("@build_bazel_rules_swift//swift:swift.bzl", "swift_binary")
 
-swift_library(
+swift_binary(
     name = "Run",
     srcs = ["main.swift"],
     module_name = "Run",

gazelle/generate.go

@@ -30,7 +30,7 @@ func genRulesFromSrcFiles(sc *swiftcfg.SwiftConfig, args language.GenerateArgs)
 	// Collect Swift files
 	swiftFiles := swift.FilterFiles(append(args.RegularFiles, args.GenFiles...))
 
-	// Do not quick exit if we do not have any Swift source files in this directory. They may be
+	// Do not quick exit if we do not have any Swift source files in this directory. There may be
 	// Swift source files in sub-directories.
 
 	// Be sure to use args.Rel when determining whether this is a module directory. We do not want

gazelle/internal/swift/file_info.go

@@ -24,6 +24,11 @@ func NewFileInfoFromReader(rel, abs string, reader io.Reader) *FileInfo {
 		Rel:    rel,
 		Abs:    abs,
 		IsTest: testSuffixes.HasSuffix(rel),
+		// There are several ways to detect a main.
+		// 1. A file named "main.swift"
+		// 2. @main annotation
+		// 3. public static func main()
+		ContainsMain: filepath.Base(rel) == "main.swift",
 	}
 
 	scanner := bufio.NewScanner(reader)

gazelle/internal/swift/module_type.go

@@ -3,7 +3,8 @@ package swift
 type ModuleType int
 
 const (
-	LibraryModuleType ModuleType = iota
+	UnknownModuleType ModuleType = iota
+	LibraryModuleType
 	BinaryModuleType
 	TestModuleType
 )