From 90e9a33e1ce3e4e7663dd67e6c1f225afaf5c206 Mon Sep 17 00:00:00 2001
From: Antonio Sanchez <cantonios@google.com>
Date: Fri, 7 May 2021 08:24:32 -0700
Subject: Fix numext::arg return type.

The cxx11 path for `numext::arg` incorrectly returned the complex type
instead of the real type, leading to compile errors. Fixed this and
added tests.

Related to !477, which uncovered the issue.
---
 Eigen/src/Core/MathFunctions.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

(limited to 'Eigen')

diff --git a/Eigen/src/Core/MathFunctions.h b/Eigen/src/Core/MathFunctions.h
index 29201214f..67b1d8263 100644
--- a/Eigen/src/Core/MathFunctions.h
+++ b/Eigen/src/Core/MathFunctions.h
@@ -592,8 +592,9 @@ struct arg_default_impl;
 
 template<typename Scalar>
 struct arg_default_impl<Scalar, true> {
+  typedef typename NumTraits<Scalar>::Real RealScalar;
   EIGEN_DEVICE_FUNC
-  static inline Scalar run(const Scalar& x)
+  static inline RealScalar run(const Scalar& x)
   {
     #if defined(EIGEN_HIP_DEVICE_COMPILE)
     // HIP does not seem to have a native device side implementation for the math routine "arg"
@@ -601,7 +602,7 @@ struct arg_default_impl<Scalar, true> {
     #else
     EIGEN_USING_STD(arg);
     #endif
-    return static_cast<Scalar>(arg(x));
+    return static_cast<RealScalar>(arg(x));
   }
 };
 
@@ -612,7 +613,7 @@ struct arg_default_impl<Scalar, false> {
   EIGEN_DEVICE_FUNC
   static inline RealScalar run(const Scalar& x)
   {
-    return (x < Scalar(0)) ? Scalar(EIGEN_PI) : Scalar(0);
+    return (x < Scalar(0)) ? RealScalar(EIGEN_PI) : RealScalar(0);
   }
 };
 #else
@@ -623,7 +624,7 @@ struct arg_default_impl
   EIGEN_DEVICE_FUNC
   static inline RealScalar run(const Scalar& x)
   {
-    return (x < Scalar(0)) ? Scalar(EIGEN_PI) : Scalar(0);
+    return (x < RealScalar(0)) ? RealScalar(EIGEN_PI) : RealScalar(0);
   }
 };
 
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