Made regression tests deterministic

Some output was uninitialized (to show an error) or timing-dependent (for the benefit of live demos) but that caused non-reproducible execution output, so I tweaked the tests to make the execution output deterministic

Author: hsutter

regression-tests/mixed-bounds-check.cpp2

@@ -2,6 +2,7 @@
 #include <vector>
 
 main: () -> int = {
-    v : std::vector = (1, 2, 3, 4, 5);
+    v : std::vector = (1, 2, 3, 4, 5, -999);
+    v.pop_back();
     std::cout << v[5] << "\n";
 }

regression-tests/mixed-initialization-safety-3.cpp2

@@ -17,12 +17,12 @@ fill: (
     out x: std::string,
     value: std::string,
     count: int
-    ) 
+    )
     [[pre: value.size() >= count, "fill: value must contain at least count elements"]]
 = {
     x = value.substr(0, count);
 }
 
 print_decorated: (x:_) = std::cout << ">> [" << x << "]\n";
 
-flip_a_coin: () -> bool = std::time(nullptr) % 2 == 0;
+flip_a_coin: () -> bool = std::rand() % 2 == 0;

regression-tests/test-results/mixed-bounds-check.cpp

@@ -12,6 +12,7 @@
 #line 3 "mixed-bounds-check.cpp2"
 
 [[nodiscard]] auto main() -> int{
-    std::vector v { 1, 2, 3, 4, 5 }; 
+    std::vector v { 1, 2, 3, 4, 5, -999 }; 
+    CPP2_UFCS_0(pop_back, v);
     std::cout << v[5] << "\n";
 }

regression-tests/test-results/mixed-initialization-safety-3.cpp

@@ -47,4 +47,4 @@ auto fill(
 
 auto print_decorated(auto const& x) -> void { std::cout << ">> [" << x << "]\n"; }
 
-[[nodiscard]] auto flip_a_coin() -> bool { return std::time(nullptr) % 2 == 0; }
+[[nodiscard]] auto flip_a_coin() -> bool { return std::rand() % 2 == 0; }

regression-tests/test-results/msvc-2022/mixed-bounds-check.cpp.execution

@@ -1 +1 @@
-4456566
+-999