Add basic tests for 'try?' migration.

Author: bjhomer

test/Migrator/optional_try_migration.swift

@@ -0,0 +1,46 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -c -update-code -swift-version 4 -primary-file %s -emit-migrated-file-path %t/optional_try_migration.result.swift -o %t/rename-func-decl.swift.remap
+// RUN: diff -u %S/optional_try_migration.swift.expected %t/optional_try_migration.result.swift
+
+func throwOrOptional() throws -> Int? {
+    return 3
+}
+
+func throwOrInt() throws -> Int {
+    return 3
+}
+
+func doubleOptional() -> Int?? {
+    return 3
+}
+
+func testIfLet() {
+    if let optionalX = try? throwOrOptional(), // This comment should be preserved
+        let y = Optional(3), // This will stay here
+        let x = optionalX // this comment will be moved
+    { 
+        print(x, y)
+        return 
+    }
+
+    if let optionalX = doubleOptional(),
+       let x = optionalX 
+    {
+        // This one shouldn't be changed
+        print(x)
+    }
+
+    if let x = try? throwOrInt(),
+       let y = try? throwOrInt() {
+        // This one shouldn't be changed
+        print(x, y)
+    }
+
+    if let optionalX = try? throwOrOptional(),
+       let optionalY = try? throwOrOptional(),
+       let x = optionalX,
+       let y = optionalY
+    {
+        print(x, y)
+    }
+}

test/Migrator/optional_try_migration.swift.expected

@@ -0,0 +1,45 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -c -update-code -swift-version 4 -primary-file %s -emit-migrated-file-path %t/optional_try_migration.result.swift -o %t/rename-func-decl.swift.remap
+// RUN: diff -u %S/optional_try_migration.swift.expected %t/optional_try_migration.result.swift
+
+func throwOrOptional() throws -> Int? {
+    return 3
+}
+
+func throwOrInt() throws -> Int {
+    return 3
+}
+
+func doubleOptional() -> Int?? {
+    return 3
+}
+
+func testIfLet() {
+    if let x = try? throwOrOptional(), // This comment should be preserved
+        let y = Optional(3) // this will stay here // this comment will be moved 
+    { 
+        print(x, y)
+        return 
+    }
+
+    if let optionalX = doubleOptional(),
+       let x = optionalX 
+    {
+        // This one shouldn't be changed
+        print(x)
+    }
+
+    if let x = try? throwOrInt(),
+       let y = try? throwOrInt() {
+        // This one shouldn't be changed
+        print(x, y)
+    }
+
+    if let optionalX = try? throwOrOptional(),
+       let optionalY = try? throwOrOptional(),
+       let x = optionalX,
+       let y = optionalY
+    {
+        print(x, y)
+    }
+}