testsuite, c++, contracts: Tests for P2900 3.4.3 part 1

Author: iains

gcc/testsuite/g++.dg/contracts/cpp26/p2900-3-3-4-part1.C

@@ -0,0 +1,19 @@
+// { dg-options "-std=c++26 -fcontracts -fcontracts-nonattr" }
+
+int bad_mr_shadow (int r)
+  post (r: r > 5) // { dg-error "contract postcondition result names must not shadow function parameters" }
+  { return r + 1; }
+
+auto no_deduced_res_types_on_non_defs (int x) // { dg-error "postconditions with deduced result name types must only appear on function definitions" }
+  pre (x > 1)
+  post (r: r > 17); 
+
+// =====
+
+auto f2() post (r : r > 0) // OK, type of r is deduced below.
+{ return 5; }
+
+template <typename T>
+auto f3 () post (r: r > 0); // OK, postcondition instantiated with template
+
+auto f4 () post (true); // OK, return value not named