Re: Go patch committed: Allow converting from slice to pointer-to-array

[Ian Lance Taylor <iant@golang.org>]

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On Mon, Aug 2, 2021 at 3:53 PM Ian Lance Taylor <iant@golang.org> wrote:
>
> The upcoming Go 1.17 release has a new language feature: it permits
> conversions from slice types to pointer-to-array types.  If the slice
> is too short, the conversion panics.  This patch implements this new
> feature in gccgo.  Bootstrapped and ran Go testsuite on
> x86_64-pc-linux-gnu.  Committed to mainline.

I didn't get the type checking right: I forgot to check that the
element types of the slice and array are identical.  Fixed with this
patches.  Bootstrapped and tested on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

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7ff2742eacee93c7e7d9262d07c2496f87d801a7
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 95b9340b42d..801e039a155 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-0a4d612e6b211780b294717503fc739bbd1f509c
+54361805bd611d896042b879ee7f6d2d4d088537
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 15c9eabc6bf..51a8b7e4322 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -3962,7 +3962,10 @@ Type_conversion_expression::do_lower(Gogo*, Named_object*,
   if (type->points_to() != NULL
       && type->points_to()->array_type() != NULL
       && !type->points_to()->is_slice_type()
-      && val->type()->is_slice_type())
+      && val->type()->is_slice_type()
+      && Type::are_identical(type->points_to()->array_type()->element_type(),
+			     val->type()->array_type()->element_type(),
+			     0, NULL))
     {
       Temporary_statement* val_temp = NULL;
       if (!val->is_multi_eval_safe())
diff --git a/gcc/go/gofrontend/types.cc b/gcc/go/gofrontend/types.cc
index 7c7b2eb8271..0c44186f507 100644
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -846,7 +846,9 @@ Type::are_convertible(const Type* lhs, const Type* rhs, std::string* reason)
   if (rhs->is_slice_type()
       && lhs->points_to() != NULL
       && lhs->points_to()->array_type() != NULL
-      && !lhs->points_to()->is_slice_type())
+      && !lhs->points_to()->is_slice_type()
+      && Type::are_identical(lhs->points_to()->array_type()->element_type(),
+			     rhs->array_type()->element_type(), 0, reason))
     return true;
 
   // An unsafe.Pointer type may be converted to any pointer type or to