PR c++/89420 - ICE with CAST_EXPR in explicit-specifier.

	* decl.c (build_explicit_specifier): Don't check
	processing_template_decl.  Call instantiation_dependent_expression_p
	instead of value_dependent_expression_p.  Call
	instantiate_non_dependent_expr_sfinae before
	build_converted_constant_expr instead of calling
	instantiate_non_dependent_expr after it.  Add
	processing_template_decl_sentinel.

	* g++.dg/cpp2a/explicit14.C: New test.

From-SVN: r269131

gcc/cp/ChangeLog

+2019-02-22  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/89420 - ICE with CAST_EXPR in explicit-specifier.
+	* decl.c (build_explicit_specifier): Don't check
+	processing_template_decl.  Call instantiation_dependent_expression_p
+	instead of value_dependent_expression_p.  Call
+	instantiate_non_dependent_expr_sfinae before
+	build_converted_constant_expr instead of calling
+	instantiate_non_dependent_expr after it.  Add
+	processing_template_decl_sentinel.
+
 2019-02-22  Thomas Schwinge  <thomas@codesourcery.com>
 
 	* parser.c (cp_parser_oacc_simple_clause): Remove parser formal

gcc/cp/decl.c

@@ -16687,12 +16687,14 @@ require_deduced_type (tree decl, tsubst_flags_t complain)
 tree
 build_explicit_specifier (tree expr, tsubst_flags_t complain)
 {
-  if (processing_template_decl && value_dependent_expression_p (expr))
+  if (instantiation_dependent_expression_p (expr))
     /* Wait for instantiation, tsubst_function_decl will handle it.  */
     return expr;
 
+  expr = instantiate_non_dependent_expr_sfinae (expr, complain);
+  /* Don't let convert_like_real create more template codes.  */
+  processing_template_decl_sentinel s;
   expr = build_converted_constant_expr (boolean_type_node, expr, complain);
-  expr = instantiate_non_dependent_expr (expr);
   expr = cxx_constant_value (expr);
   return expr;
 }

gcc/testsuite/ChangeLog

+2019-02-22  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/89420 - ICE with CAST_EXPR in explicit-specifier.
+	* g++.dg/cpp2a/explicit14.C: New test.
+
 2019-02-22  Matthew Malcomson  <matthew.malcomson@arm.com>
 
 	PR target/89324

gcc/testsuite/g++.dg/cpp2a/explicit14.C

+// PR c++/89420
+// { dg-do compile { target c++2a } }
+
+template<typename>
+struct S {
+  explicit(int(1)) S(int);
+  explicit(int{1}) S(int, int);
+};
+
+S<int> s(1);
+S<int> s2(1, 2);