Add convenience initializer for ReturnClause

Author: kimdv

Sources/SwiftSyntaxBuilder/StringConvenienceInitializers.swift

@@ -40,6 +40,12 @@ extension String: ExpressibleAsBinaryOperatorExpr {
   }
 }
 
+extension String: ExpressibleAsReturnClause {
+  public func createReturnClause() -> ReturnClause {
+    ReturnClause(returnType: self)
+  }
+}
+
 /// Default conformance to `ExpressibleByTypeBuildable`
 extension String {
   public func createTypeBuildable() -> TypeBuildable {

Tests/SwiftSyntaxBuilderTest/FunctionTests.swift

@@ -14,7 +14,7 @@ final class FunctionTests: XCTestCase {
       ReturnStmt(expression: IntegerLiteralExpr(digits: "n"))
     })
 
-    let signature = FunctionSignature(input: input, output: ReturnClause(returnType: "Int"))
+    let signature = FunctionSignature(input: input, output: "Int")
 
 
     let codeBlock = CodeBlock(statementsBuilder: {

Tests/SwiftSyntaxBuilderTest/ReturnClauseTests.swift

@@ -0,0 +1,25 @@
+import XCTest
+import SwiftSyntax
+import SwiftSyntaxBuilder
+
+final class ReturnClauseTests: XCTestCase {
+  func testReturnClause() {
+    let leadingTrivia = Trivia.garbageText("␣")
+
+    let testCases: [UInt: (ExpressibleAsReturnClause, String)] = [
+      #line: (ReturnClause(returnType: "Int"), "␣-> Int"),
+      #line: ("Int", "␣-> Int"),
+    ]
+
+    for (line, testCase) in testCases {
+      let (builder, expected) = testCase
+      let returnClause = builder.createReturnClause()
+      let syntax = returnClause.buildSyntax(format: Format(), leadingTrivia: leadingTrivia)
+
+      var text = ""
+      syntax.write(to: &text)
+
+      XCTAssertEqual(text, expected, line: line)
+    }
+  }
+}