[CSSimplify] Skip transitive conformance check if argument is CGFloat or Double

lib/Sema/CSSimplify.cpp

@@ -9247,6 +9247,14 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyTransitivelyConformsTo(
   if (resolvedTy->isTypeVariableOrMember())
     return formUnsolved();
 
+  // There is an implicit conversion between `CGFloat` and `Double` types
+  // so if `CGFloat`/`Double` argument doesn't satisfy the requirement it's
+  // possible that the generic parameter it's passed to be inferred as a
+  // the other type from context and the requirement to be satisfied through
+  // this implicit conversion.
+  if (resolvedTy->isCGFloat() || resolvedTy->isDouble())
+    return SolutionKind::Solved;
+
   // If the composition consists of a class + protocol,
   // we can't check conformance of the argument because
   // parameter could pick one of the components.

test/Constraints/transitive_conformances_and_cgfloat_double.swift

@@ -0,0 +1,34 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -debug-constraints -verify %s 2>%t.err
+// RUN: %FileCheck %s < %t.err
+
+// REQUIRES: objc_interop
+
+// rdar://153461854
+
+import CoreGraphics
+
+// There is no better way to check this at the moment because diagnostic mode would produce
+// a valid solution for this example. We need to make sure that the solution is produced in
+// normal mode instead.
+
+ let _ = { (point: CGFloat) in
+   let _: SIMD2<Double>? = SIMD2(point, point)
+ }
+
+// CHECK-NOT: failed constraint CGFloat transitive conformance to SIMDScalar
+// CHECK-NOT: Attempting to salvage
+
+protocol P {}
+extension CGFloat: P {}
+
+struct S<T> {}
+
+func foo<T: P>(_ x: T) -> S<T> { .init() }
+
+_ = { (x: Double) in
+  let _: S<CGFloat> = foo(x)
+}
+
+// CHECK-NOT: failed constraint CGFloat transitive conformance to SIMDScalar
+// CHECK-NOT: Attempting to salvage