Bug: Method Call with Generic Invariance Swaps Parameter List with Right Hand Side of Comparison

[orchetect]

Issue

This is an odd edge-case bug where when a method call has inline generics in a comparison expression, the parameter list of the method call is swapped with the right-hand side content of the expression when the right-hand side is a variable and not a literal.

Conditions

The issue can be reproduced with:

• SwiftFormat 0.55.3
• factory default SwiftFormat configuration
• specifying any Swift version - I tried all versions from Swift 5.0 through 6.0 and they all produce the same incorrect output
• issue still happens when parameter list is non-empty

Example

Original code:

func method() -> Int { 123 }
func method() -> String { "string" }

let intVariable: Int = 123

enum IntEnum: Int {
    case foo = 123
}

let stringVariable: String = "string"

enum StringEnum: Int {
    case foo = "string"
}

func test() {
    print(method<Int>() == 123)
    print(method<Int>() == intVariable)
    print(method<Int>() == IntEnum.foo.rawValue)
    
    print(method<String>() == "string")
    print(method<String>() == stringVariable)
    print(method<String>() == StringEnum.foo.rawValue)
}

SwiftFormat output (diff):

-    print(method<Int>() == intVariable)
+    print(method<Int>intVariable == ())
-    print(method<Int>() == IntEnum.foo.rawValue)
+    print(method<Int>IntEnum.foo.rawValue == ())

-    print(method<String>() == stringVariable)
+    print(method<String>stringVariable == ())
-    print(method<String>() == StringEnum.foo.rawValue)
+    print(method<String>StringEnum.foo.rawValue == ())