[test] Add regression test for SR-9090

We didn't use to accept pointer conversions passed
to double optional parameters, but do now.

Author: hamishknight

test/Constraints/valid_pointer_conversions.swift

@@ -7,8 +7,30 @@ func foo(_ a: [[UInt8]], _ p: [UnsafeRawPointer]) {
 // rdar://problem/44658089
 func takesPtr(_: UnsafePointer<UInt8>) {}
 
+func takesDoubleOptionalPtr(_ x: UnsafeRawPointer??) {}
+func takesMutableDoubleOptionalPtr(_ x: UnsafeMutableRawPointer??) {}
+func takesMutableDoubleOptionalTypedPtr(_ x: UnsafeMutablePointer<Double>??) {}
+
 func givesPtr(_ str: String) {
   takesPtr(UnsafePointer(str)) // expected-warning {{initialization of 'UnsafePointer<UInt8>' results in a dangling pointer}}
   // expected-note @-1 {{implicit argument conversion from 'String' to 'UnsafePointer<UInt8>' produces a pointer valid only for the duration of the call to 'init(_:)'}}
   // expected-note@-2 {{use the 'withCString' method on String in order to explicitly convert argument to pointer valid for a defined scope}}
+
+  var i = 0
+  var d = 0.0
+  var arr = [1, 2, 3]
+
+  // SR-9090: Allow double optional promotion for pointer conversions.
+  takesDoubleOptionalPtr(&arr)
+  takesDoubleOptionalPtr(arr)
+  takesDoubleOptionalPtr(str)
+  takesMutableDoubleOptionalPtr(&i)
+  takesMutableDoubleOptionalPtr(&arr)
+  takesMutableDoubleOptionalTypedPtr(&d)
+
+  takesDoubleOptionalPtr(i) // expected-error {{cannot convert value of type 'Int' to expected argument type 'UnsafeRawPointer??'}}
+  takesMutableDoubleOptionalPtr(arr) // expected-error {{cannot convert value of type '[Int]' to expected argument type 'UnsafeMutableRawPointer??'}}
+
+  // FIXME(SR-12382): Poor diagnostic.
+  takesMutableDoubleOptionalTypedPtr(&i) // expected-error {{type of expression is ambiguous without more context}}
 }