[AutoDiff upstream] Test forward-mode differentiation diagnostics.

Author: dan-zheng

test/AutoDiff/SILOptimizer/forward_mode_diagnostics.swift

@@ -0,0 +1,150 @@
+// RUN: %target-swift-frontend -enable-experimental-forward-mode-differentiation -emit-sil -verify %s
+
+// Test forward-mode differentiation transform diagnostics.
+
+// TODO: Move these tests back into `autodiff_diagnostics.swift` once
+// forward mode reaches feature parity with reverse mode.
+
+import _Differentiation
+
+//===----------------------------------------------------------------------===//
+// Basic function
+//===----------------------------------------------------------------------===//
+
+@differentiable
+func basic(_ x: Float) -> Float {
+  return x
+}
+
+//===----------------------------------------------------------------------===//
+// Control flow
+//===----------------------------------------------------------------------===//
+
+// expected-error @+1 {{function is not differentiable}}
+@differentiable
+// expected-note @+2 {{when differentiating this function definition}}
+// expected-note @+1 {{forward-mode differentiation does not yet support control flow}}
+func cond(_ x: Float) -> Float {
+  if x > 0 {
+    return x * x
+  }
+  return x + x
+}
+
+//===----------------------------------------------------------------------===//
+// Non-varied results
+//===----------------------------------------------------------------------===//
+
+@differentiable
+func nonVariedResult(_ x: Float) -> Float {
+  // TODO(TF-788): Re-enable non-varied result warning.
+  // xpected-warning @+1 {{result does not depend on differentiation arguments and will always have a zero derivative; do you want to use 'withoutDerivative(at:)'?}} {{10-10=withoutDerivative(at:}} {{15-15=)}}
+  return 0
+}
+
+//===----------------------------------------------------------------------===//
+// Multiple results
+//===----------------------------------------------------------------------===//
+
+// TODO(TF-983): Support differentiation of multiple results.
+/*
+func multipleResults(_ x: Float) -> (Float, Float) {
+  return (x, x)
+}
+@differentiable
+func usesMultipleResults(_ x: Float) -> Float {
+  let tuple = multipleResults(x)
+  return tuple.0 + tuple.1
+}
+*/
+
+//===----------------------------------------------------------------------===//
+// `inout` parameter differentiation
+//===----------------------------------------------------------------------===//
+
+// expected-error @+1 {{function is not differentiable}}
+@differentiable
+// expected-note @+1 {{when differentiating this function definition}}
+func activeInoutParamNonactiveInitialResult(_ x: Float) -> Float {
+  var result: Float = 1
+  // expected-note @+1 {{cannot differentiate through 'inout' arguments}}
+  result += x
+  return result
+}
+
+// expected-error @+1 {{function is not differentiable}}
+@differentiable
+// expected-note @+1 {{when differentiating this function definition}}
+func activeInoutParamTuple(_ x: Float) -> Float {
+  var tuple = (x, x)
+  // expected-note @+1 {{cannot differentiate through 'inout' arguments}}
+  tuple.0 *= x
+  return x * tuple.0
+}
+
+// expected-error @+1 {{function is not differentiable}}
+@differentiable
+// expected-note @+2 {{when differentiating this function definition}}
+// expected-note @+1 {{forward-mode differentiation does not yet support control flow}}
+func activeInoutParamControlFlow(_ array: [Float]) -> Float {
+  var result: Float = 1
+  for i in withoutDerivative(at: array).indices {
+    result += array[i]
+  }
+  return result
+}
+
+struct Mut: Differentiable {}
+extension Mut {
+  @differentiable(wrt: x)
+  mutating func mutatingMethod(_ x: Mut) {}
+}
+
+// FIXME(TF-984): Forward-mode crash due to unset tangent buffer.
+/*
+@differentiable(wrt: x)
+func nonActiveInoutParam(_ nonactive: inout Mut, _ x: Mut) -> Mut {
+  return nonactive.mutatingMethod(x)
+}
+*/
+
+// FIXME(TF-984): Forward-mode crash due to unset tangent buffer.
+/*
+@differentiable(wrt: x)
+func activeInoutParamMutatingMethod(_ x: Mut) -> Mut {
+  var result = x
+  result = result.mutatingMethod(result)
+  return result
+}
+*/
+
+// FIXME(TF-984): Forward-mode crash due to unset tangent buffer.
+/*
+@differentiable(wrt: x)
+func activeInoutParamMutatingMethodVar(_ nonactive: inout Mut, _ x: Mut) -> Mut {
+  var result = nonactive
+  result = result.mutatingMethod(x)
+  return result
+}
+*/
+
+// FIXME(TF-984): Forward-mode crash due to unset tangent buffer.
+/*
+@differentiable(wrt: x)
+func activeInoutParamMutatingMethodTuple(_ nonactive: inout Mut, _ x: Mut) -> Mut {
+  var result = (nonactive, x)
+  let result2 = result.0.mutatingMethod(result.0)
+  return result2
+}
+*/
+
+//===----------------------------------------------------------------------===//
+// Subset parameter differentiation thunks
+//===----------------------------------------------------------------------===//
+
+// FIXME(SR-13046): Non-differentiability diagnostic crash due to invalid source location.
+/*
+func testNoDerivativeParameter(_ f: @differentiable (Float, @noDerivative Float) -> Float) -> Float {
+  return derivative(at: 2, 3) { (x, y) in f(x * x, y) }
+}
+*/