[gcc r12-1306] c++: Test for mixed string literal concatenation

[gcc r12-1306] c++: Test for mixed string literal concatenation

[Jason Merrill]

https://gcc.gnu.org/g:924e02553af64b10c485711d635c0bc0265a8743

commit r12-1306-g924e02553af64b10c485711d635c0bc0265a8743
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Jun 8 14:38:42 2021 -0400

    c++: Test for mixed string literal concatenation
    
    From wg21.link/p2201r1
    
    gcc/cp/ChangeLog:
    
            * parser.c (cp_parser_string_literal): Adjust diagnostic.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp23/mixed-concat1.C: New test.

Diff:
---
 gcc/cp/parser.c                            |  4 ++--
 gcc/testsuite/g++.dg/cpp23/mixed-concat1.C | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 24f248af11c..d59a829d0b9 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -4378,8 +4378,8 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
 		  rich_location rich_loc (line_table, tok->location);
 		  rich_loc.add_range (last_tok_loc);
 		  error_at (&rich_loc,
-			    "unsupported non-standard concatenation "
-			    "of string literals");
+			    "concatenation of string literals with "
+			    "conflicting encoding prefixes");
 		}
 	    }
 
diff --git a/gcc/testsuite/g++.dg/cpp23/mixed-concat1.C b/gcc/testsuite/g++.dg/cpp23/mixed-concat1.C
new file mode 100644
index 00000000000..d69fafc862d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/mixed-concat1.C
@@ -0,0 +1,21 @@
+// Test from P2201R1
+// { dg-do compile { target c++11 } }
+
+void f() {
+
+  { auto a = L"" u""; }		// { dg-error "concatenation" }
+  { auto a = L"" u8""; }	// { dg-error "concatenation" }
+  { auto a = L"" U""; }		// { dg-error "concatenation" }
+
+  { auto a = u8"" L""; }	// { dg-error "concatenation" }
+  { auto a = u8"" u""; }	// { dg-error "concatenation" }
+  { auto a = u8"" U""; }	// { dg-error "concatenation" }
+
+  { auto a = u"" L""; }		// { dg-error "concatenation" }
+  { auto a = u"" u8""; }	// { dg-error "concatenation" }
+  { auto a = u"" U""; }		// { dg-error "concatenation" }
+
+  { auto a = U"" L""; }		// { dg-error "concatenation" }
+  { auto a = U"" u""; }		// { dg-error "concatenation" }
+  { auto a = U"" u8""; }	// { dg-error "concatenation" }
+}