Backported from mainline

	2017-11-27  Jakub Jelinek  <jakub@redhat.com>

	PR c++/81888
	* parser.c (cp_parser_decomposition_declaration): Reject just
	BRACE_ENCLOSED_INITIALIZER_P initializers with nelts != 1 rather
	than all such CONSTRUCTORs, and only if is_direct_init is true.

	* g++.dg/cpp1z/decomp30.C: Add a test for structured binding with
	= {} and = { a, a } initializers.
	* g++.dg/cpp1z/decomp31.C: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-7-branch@255719 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 32 insertions, 1 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index c303347f075..a47d90bc96d 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -3,6 +3,11 @@
 	Backported from mainline
 	2017-11-27  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/81888
+	* parser.c (cp_parser_decomposition_declaration): Reject just
+	BRACE_ENCLOSED_INITIALIZER_P initializers with nelts != 1 rather
+	than all such CONSTRUCTORs, and only if is_direct_init is true.
+
 	PR c++/81675
 	* cp-gimplify.c (cp_fold) <case COND_EXPR>: Don't return immediately
 	for VOID_TYPE_P COND_EXPRs, instead fold the operands and if op0 is
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index b060ac8dcd1..4509397e414 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -13048,7 +13048,8 @@ cp_parser_decomposition_declaration (cp_parser *parser,
       if (initializer == NULL_TREE
 	  || (TREE_CODE (initializer) == TREE_LIST
 	      && TREE_CHAIN (initializer))
-	  || (TREE_CODE (initializer) == CONSTRUCTOR
+	  || (is_direct_init
+	      && BRACE_ENCLOSED_INITIALIZER_P (initializer)
 	      && CONSTRUCTOR_NELTS (initializer) != 1))
 	{
 	  error_at (loc, "invalid initializer for structured binding "
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e312f0f0121..c8ef0b39442 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -3,6 +3,11 @@
 	Backported from mainline
 	2017-11-27  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/81888
+	* g++.dg/cpp1z/decomp30.C: Add a test for structured binding with
+	= {} and = { a, a } initializers.
+	* g++.dg/cpp1z/decomp31.C: New test.
+
 	PR c++/81675
 	* g++.dg/warn/pr81675.C: New test.
 
diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp30.C b/gcc/testsuite/g++.dg/cpp1z/decomp30.C
index 23115ad1082..cca15ed126b 100644
--- a/gcc/testsuite/g++.dg/cpp1z/decomp30.C
+++ b/gcc/testsuite/g++.dg/cpp1z/decomp30.C
@@ -10,3 +10,5 @@ auto [j, k] { a, a };	// { dg-error "invalid initializer for structured binding
 auto [l, m] = { a };	// { dg-error "deducing from brace-enclosed initializer list requires" }
 auto [n, o] {};		// { dg-error "invalid initializer for structured binding declaration" }
 auto [p, q] ();		// { dg-error "invalid initializer for structured binding declaration" }
+auto [r, s] = {};	// { dg-error "deducing from brace-enclosed initializer list requires" }
+auto [t, u] = { a, a };	// { dg-error "deducing from brace-enclosed initializer list requires" }
diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp31.C b/gcc/testsuite/g++.dg/cpp1z/decomp31.C
new file mode 100644
index 00000000000..04b2516dada
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/decomp31.C
@@ -0,0 +1,18 @@
+// PR c++/81888
+// { dg-do compile { target c++1z } }
+
+struct S {
+  bool s = true;
+};
+
+auto [a] = S{};
+
+template <class T>
+bool
+foo () noexcept
+{
+  auto [c] = T{};
+  return c;
+}
+
+const bool b = foo<S> ();