PR c++/89158 - by-value capture of constexpr variable broken.

	* call.c (convert_like_real) <case ck_user>: Call mark_exp_read
	instead of mark_rvalue_use.

	* g++.dg/cpp0x/lambda/lambda-89158.C: New test.

From-SVN: r268561

gcc/cp/ChangeLog

+2019-02-05  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/89158 - by-value capture of constexpr variable broken.
+	* call.c (convert_like_real) <case ck_user>: Call mark_exp_read
+	instead of mark_rvalue_use.
+
 2019-02-05  Alexandre Oliva <aoliva@redhat.com>
 
 	PR c++/87770

gcc/cp/call.c

@@ -7006,7 +7006,9 @@ convert_like_real (conversion *convs, tree expr, tree fn, int argnum,
 	    return expr;
 	  }
 
-	expr = mark_rvalue_use (expr);
+	/* We don't know here whether EXPR is being used as an lvalue or
+	   rvalue, but we know it's read.  */
+	mark_exp_read (expr);
 
 	/* Pass LOOKUP_NO_CONVERSION so rvalue/base handling knows not to allow
 	   any more UDCs.  */

gcc/testsuite/ChangeLog

+2019-02-05  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/89158 - by-value capture of constexpr variable broken.
+	* g++.dg/cpp0x/lambda/lambda-89158.C: New test.
+
 2019-02-05  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* gcc.dg/vect/pr84711.c: Use -Wno-psabi.

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-89158.C

+// PR c++/89158
+// { dg-do compile { target c++11 } }
+
+struct T { T(const int&); };
+void Func(T);
+
+void test()
+{
+  constexpr int Val = 42;
+  [Val]() { Func(Val); };
+}