From fbf4bb738db00b2b6c72874bc61170fbc603c2c6 Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Fri, 14 Dec 2018 17:00:17 -0800
Subject: [PATCH] [SIMD] Add CustomDebugStringConvertible conformance for SIMD
 types.

The old SIMD types had a conformance to CustomDebugStringConvertible,
but the new ones do not, causing a source compatibility
regression. Add back a CustomDebugStringConvertible conformance.

Fixes rdar://problem/46746829.
---
 stdlib/public/core/SIMDVectorTypes.swift.gyb | 8 ++++++++
 test/stdlib/simd.swift.gyb                   | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/stdlib/public/core/SIMDVectorTypes.swift.gyb b/stdlib/public/core/SIMDVectorTypes.swift.gyb
index b5d91cecf7852..d079d77494fa7 100644
--- a/stdlib/public/core/SIMDVectorTypes.swift.gyb
+++ b/stdlib/public/core/SIMDVectorTypes.swift.gyb
@@ -109,6 +109,14 @@ public extension SIMD${n} where Scalar : FixedWidthInteger {
   }
 }
 
+extension SIMD${n} : CustomDebugStringConvertible {
+  /// Debug string representation
+  public var debugDescription: String {
+    return "SIMD${n}<\(Scalar.self)>(${', '.join(map(lambda c:
+                       '\\(self['+ str(c) + '])',
+                       xrange(n)))})"
+  }
+}
 
 public extension SIMD${n} where Scalar : BinaryFloatingPoint {
   @inlinable
diff --git a/test/stdlib/simd.swift.gyb b/test/stdlib/simd.swift.gyb
index afadc168a5286..84bedf3570631 100644
--- a/test/stdlib/simd.swift.gyb
+++ b/test/stdlib/simd.swift.gyb
@@ -313,5 +313,10 @@ simdTestSuite.test("matrix elements") {
 % end # for type
 }
 
+simdTestSuite.test("debug description") {
+  expectEqual("SIMD2<Float>(1.0, 2.5)",
+    SIMD2<Float>(1.0, 2.5).debugDescription)
+}
+
 runAllTests()