diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 2852093d624..45206c236c1 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -8129,6 +8129,17 @@ cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
 	  TREE_TYPE (decl) = error_mark_node;
 	  return;
 	}
+      /* As in start_decl_1, complete so TREE_READONLY is set properly.  */
+      if (!processing_template_decl
+	  && !type_uses_auto (type)
+	  && !COMPLETE_TYPE_P (complete_type (type)))
+	{
+	  error_at (location_of (decl),
+		    "deduced type %qT for %qD is incomplete", type, decl);
+	  cxx_incomplete_type_inform (type);
+	  TREE_TYPE (decl) = error_mark_node;
+	  return;
+	}
       cp_apply_type_quals_to_decl (cp_type_quals (type), decl);
     }
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-77482.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-77482.C
index 6f5c91621ce..bed66c7fa81 100644
--- a/gcc/testsuite/g++.dg/cpp0x/constexpr-77482.C
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-77482.C
@@ -3,4 +3,4 @@
 
 constexpr auto x;	// { dg-error "declaration\[^\n\r]*has no initializer" }
 extern struct S s;
-constexpr auto y = s;	// { dg-error "has incomplete type" }
+constexpr auto y = s;	// { dg-error "incomplete" }
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-const1.C b/gcc/testsuite/g++.dg/cpp0x/initlist-const1.C
new file mode 100644
index 00000000000..de807316be6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-const1.C
@@ -0,0 +1,7 @@
+// { dg-do compile { target c++11 } }
+
+#include <initializer_list>
+
+const auto x = { 1, 2 };
+
+// { dg-final { scan-assembler-not {\.data} } }
diff --git a/gcc/testsuite/g++.dg/cpp1y/auto-fn27.C b/gcc/testsuite/g++.dg/cpp1y/auto-fn27.C
index c019d9ef583..b22647a38de 100644
--- a/gcc/testsuite/g++.dg/cpp1y/auto-fn27.C
+++ b/gcc/testsuite/g++.dg/cpp1y/auto-fn27.C
@@ -31,7 +31,7 @@ F<T>::bar (const G &)
 {
   auto s = I;
   typedef decltype (s) L;
-  auto u =[&](L) { auto t = foo (J::K (), 0); }; // { dg-error "25:declared void" }
+  auto u =[&](L) { auto t = foo (J::K (), 0); }; // { dg-error "25:incomplete|void" }
 }
 struct B {
   typedef int G;
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-variadic22.C b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-variadic22.C
index 670c598a865..9c02d0715c1 100644
--- a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-variadic22.C
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-variadic22.C
@@ -4,7 +4,7 @@
 template <typename T>
 auto f (T)
 {
-  auto a = [](auto ... i)	// { dg-prune-output "incomplete type" }
+  auto a = [](auto ... i)	// { dg-prune-output "incomplete" }
   {
     int x[][i] = { 0 };		// { dg-error "not expanded" }
   }();
diff --git a/gcc/testsuite/g++.dg/cpp1z/decomp54.C b/gcc/testsuite/g++.dg/cpp1z/decomp54.C
index 1bee772d5ba..1094329e69d 100644
--- a/gcc/testsuite/g++.dg/cpp1z/decomp54.C
+++ b/gcc/testsuite/g++.dg/cpp1z/decomp54.C
@@ -3,9 +3,9 @@
 // { dg-options "" }
 
 extern int a[];
-auto [b] { a };	// { dg-error "has incomplete type" }
+auto [b] { a };	// { dg-error "incomplete" }
 		// { dg-warning "only available with" "" { target c++14_down } .-1 }
-auto [c] = a;	// { dg-error "has incomplete type" }
+auto [c] = a;	// { dg-error "incomplete" }
 		// { dg-warning "only available with" "" { target c++14_down } .-1 }
 extern int d[0];
 auto [e] { d };	// { dg-error "too many initializers for" }
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-37.C b/gcc/testsuite/g++.dg/warn/Wunused-var-37.C
new file mode 100644
index 00000000000..54e76ac4e11
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-37.C
@@ -0,0 +1,64 @@
+// Tangentially to PR c++/80351
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wunused-variable" }
+#include <initializer_list>
+
+// Warnings:
+static int           int_s1  = 0; // { dg-warning "defined but not used" }
+static int           int_s2  = 0; // { dg-warning "defined but not used" }
+inline static int    int_is1 = 0; // { dg-warning "defined but not used" }
+inline static int    int_is2 = 0; // { dg-warning "defined but not used" }
+// No warnings:
+constexpr static int int_cs1 = 0; // { dg-bogus "defined but not used" }
+constexpr static int int_cs2 = 0; // { dg-bogus "defined but not used" }
+int                  int_1   = 0; // { dg-bogus "defined but not used" }
+int                  int_2   = 0; // { dg-bogus "defined but not used" }
+inline int           int_i1  = 0; // { dg-bogus "defined but not used" }
+inline int           int_i2  = 0; // { dg-bogus "defined but not used" }
+constexpr int        int_c1  = 0; // { dg-bogus "defined but not used" }
+constexpr int        int_c2  = 0; // { dg-bogus "defined but not used" }
+
+// Warnings:
+static auto           int_as1  = 0; // { dg-warning "defined but not used" }
+static auto           int_as2  = 0; // { dg-warning "defined but not used" }
+inline static auto    int_ais1 = 0; // { dg-warning "defined but not used" }
+inline static auto    int_ais2 = 0; // { dg-warning "defined but not used" }
+// No warnings:
+constexpr static auto int_acs1 = 0; // { dg-bogus "defined but not used" }
+constexpr static auto int_acs2 = 0; // { dg-bogus "defined but not used" }
+auto                  int_a1   = 0; // { dg-bogus "defined but not used" }
+auto                  int_a2   = 0; // { dg-bogus "defined but not used" }
+inline auto           int_ai1  = 0; // { dg-bogus "defined but not used" }
+inline auto           int_ai2  = 0; // { dg-bogus "defined but not used" }
+constexpr auto        int_ac1  = 0; // { dg-bogus "defined but not used" }
+constexpr auto        int_ac2  = 0; // { dg-bogus "defined but not used" }
+
+// Warnings:
+static std::initializer_list<int>           il_s1  = {0, 1}; // { dg-warning "defined but not used" }
+static std::initializer_list<int>           il_s2  = {0, 1}; // { dg-warning "defined but not used" }
+inline static std::initializer_list<int>    il_is1 = {0, 1}; // { dg-warning "defined but not used" }
+inline static std::initializer_list<int>    il_is2 = {0, 1}; // { dg-warning "defined but not used" }
+// No warnings:
+constexpr static std::initializer_list<int> il_cs1 = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr static std::initializer_list<int> il_cs2 = {0, 1}; // { dg-bogus "defined but not used" }
+std::initializer_list<int>                  il_1   = {0, 1}; // { dg-bogus "defined but not used" }
+std::initializer_list<int>                  il_2   = {0, 1}; // { dg-bogus "defined but not used" }
+inline std::initializer_list<int>           il_i1  = {0, 1}; // { dg-bogus "defined but not used" }
+inline std::initializer_list<int>           il_i2  = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr std::initializer_list<int>        il_c1  = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr std::initializer_list<int>        il_c2  = {0, 1}; // { dg-bogus "defined but not used" }
+
+// Warnings:
+static auto           il_as1  = {0, 1}; // { dg-warning "defined but not used" }
+static auto           il_as2  = {0, 1}; // { dg-warning "defined but not used" }
+inline static auto    il_ais1 = {0, 1}; // { dg-warning "defined but not used" }
+inline static auto    il_ais2 = {0, 1}; // { dg-warning "defined but not used" }
+// No warnings:
+constexpr static auto il_acs1 = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr static auto il_acs2 = {0, 1}; // { dg-bogus "defined but not used" }
+auto                  il_a1   = {0, 1}; // { dg-bogus "defined but not used" }
+auto                  il_a2   = {0, 1}; // { dg-bogus "defined but not used" }
+inline auto           il_ai1  = {0, 1}; // { dg-bogus "defined but not used" }
+inline auto           il_ai2  = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr auto        il_ac1  = {0, 1}; // { dg-bogus "defined but not used" }
+constexpr auto        il_ac2  = {0, 1}; // { dg-bogus "defined but not used" }
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-38.C b/gcc/testsuite/g++.dg/warn/Wunused-var-38.C
new file mode 100644
index 00000000000..3d34bc8e8c1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-38.C
@@ -0,0 +1,16 @@
+// PR c++/80351
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-variable" }
+#include <initializer_list>
+
+constexpr auto int_1 = 1; // { dg-bogus "defined but not used" }
+constexpr auto int_2 = 2; // { dg-bogus "defined but not used" }
+
+constexpr auto il_int_1 = {3, 3}; // { dg-bogus "defined but not used" "Triggered by PR80351" }
+constexpr auto il_int_2 = {4, 4}; // { dg-bogus "defined but not used" "Not triggered by PR80351" }
+
+constexpr auto il_uint_1 = {5u, 5u}; // { dg-bogus "defined but not used" "Triggered by PR80351" }
+constexpr auto il_uint_2 = {6u, 6u}; // { dg-bogus "defined but not used" "Not triggered by PR80351" }
+
+constexpr auto uint_1 = 7u; // { dg-bogus "defined but not used" }
+constexpr auto uint_2 = 8u; // { dg-bogus "defined but not used" }
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-39.C b/gcc/testsuite/g++.dg/warn/Wunused-var-39.C
new file mode 100644
index 00000000000..d25a74c43c2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-39.C
@@ -0,0 +1,16 @@
+// PR c++/80351
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wunused-variable" }
+#include <initializer_list>
+
+const auto int_1 = 1; // { dg-bogus "defined but not used" }
+const auto int_2 = 2; // { dg-bogus "defined but not used" }
+
+const auto il_int_1 = {3, 3}; // { dg-bogus "defined but not used" "Triggered by PR80351" }
+const auto il_int_2 = {4, 4}; // { dg-bogus "defined but not used" "Not triggered by PR80351" }
+
+const auto il_uint_1 = {5u, 5u}; // { dg-bogus "defined but not used" "Triggered by PR80351" }
+const auto il_uint_2 = {6u, 6u}; // { dg-bogus "defined but not used" "Not triggered by PR80351" }
+
+const auto uint_1 = 7u; // { dg-bogus "defined but not used" }
+const auto uint_2 = 8u; // { dg-bogus "defined but not used" }
