doc: mention testing/quick RNG seeding change in Go 1.9 notes

Also reword the testing/quick.Config field docs to conform to the
normal subject-first style. Without that style, godoc links
/pkg/testing/quick/#Config.Rand to the wrong line, since it doesn't
recognize the preceding comment as necessarily being attached.

Fixes #20809

Change-Id: I9aebbf763eed9b1ab1a153fa11850d88a65571c6
Reviewed-on: https://go-review.googlesource.com/46910
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/doc/go1.9.html b/doc/go1.9.html
index 3704f55835dc8f1feec6319291e6ae080c27b3e1..262d468e3f7410aac1f8ffc3db57c6b3c27cd151 100644 (file)
--- a/doc/go1.9.html
+++ b/doc/go1.9.html
@@ -786,10 +786,18 @@ CL 40331: https://golang.org/cl/40331: cmd/link,runtime/cgo: enable PT_TLS gener
 <dl id="testing/quick"><dt><a href="/pkg/testing/quick/">testing/quick</a></dt>
   <dd>
     <p><!-- CL 39152 -->
-         The package now chooses values in the full range when
-         generating <code>int64</code> and <code>uint64</code> random
-         numbers; in earlier releases generated values were always
-         limited to the [-2<sup>62</sup>, 2<sup>62</sup>) range.
+      The package now chooses values in the full range when
+      generating <code>int64</code> and <code>uint64</code> random
+      numbers; in earlier releases generated values were always
+      limited to the [-2<sup>62</sup>, 2<sup>62</sup>) range.
+    </p>
+
+    <p>
+      In previous releases, using a nil
+      <a href="/pkg/testing/quick/#Config.Rand"><code>Config.Rand</code></a>
+      value caused the same deterministic random number generator to be used.
+      It now uses a random number generator seeded on the current time.
+      For the old behavior, use <code>rand.New(rand.NewSource(0))</code>.
     </p>
 
 </dl><!-- testing/quick -->

diff --git a/src/testing/quick/quick.go b/src/testing/quick/quick.go
index 94d873988aea7b4121a9cb8179873ea59e6b0caa..0457fc7571b9cec554b7ae6c9e84d96d1b38c709 100644 (file)
--- a/src/testing/quick/quick.go
+++ b/src/testing/quick/quick.go
@@ -175,19 +175,20 @@ func sizedValue(t reflect.Type, rand *rand.Rand, size int) (value reflect.Value,
 
 // A Config structure contains options for running a test.
 type Config struct {
-       // MaxCount sets the maximum number of iterations. If zero,
-       // MaxCountScale is used.
+       // MaxCount sets the maximum number of iterations.
+       // If zero, MaxCountScale is used.
        MaxCount int
-       // MaxCountScale is a non-negative scale factor applied to the default
-       // maximum. If zero, the default is unchanged.
+       // MaxCountScale is a non-negative scale factor applied to the
+       // default maximum.
+       // If zero, the default is unchanged.
        MaxCountScale float64
-       // If non-nil, rand is a source of random numbers. Otherwise a default
-       // pseudo-random source will be used.
+       // Rand specifies a source of random numbers.
+       // If nil, a default pseudo-random source will be used.
        Rand *rand.Rand
-       // If non-nil, the Values function generates a slice of arbitrary
-       // reflect.Values that are congruent with the arguments to the function
-       // being tested. Otherwise, the top-level Value function is used
-       // to generate them.
+       // Values specifies a function to generate a slice of
+       // arbitrary reflect.Values that are congruent with the
+       // arguments to the function being tested.
+       // If nil, the top-level Value function is used to generate them.
        Values func([]reflect.Value, *rand.Rand)
 }