test: Add test cases for the new capture behavior

test/stage1/behavior/for.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const expect = std.testing.expect;
+const expectEqual = std.testing.expectEqual;
 const mem = std.mem;
 
 test "continue in for loop" {
@@ -142,3 +143,30 @@ test "for with null and T peer types and inferred result location type" {
     S.doTheTest(&[_]u8{ 1, 2 });
     comptime S.doTheTest(&[_]u8{ 1, 2 });
 }
+
+test "for copies its payload" {
+    const S = struct {
+        fn doTheTest() void {
+            var x = [_]usize{ 1, 2, 3 };
+            for (x) |value, i| {
+                // Modify the original array
+                x[i] += 99;
+                expectEqual(value, i + 1);
+            }
+        }
+    };
+    S.doTheTest();
+    comptime S.doTheTest();
+}
+
+test "for on slice with allowzero ptr" {
+    const S = struct {
+        fn doTheTest(slice: []u8) void {
+            var ptr = @ptrCast([*]allowzero u8, slice.ptr)[0..slice.len];
+            for (ptr) |x, i| expect(x == i + 1);
+            for (ptr) |*x, i| expect(x.* == i + 1);
+        }
+    };
+    S.doTheTest(&[_]u8{ 1, 2, 3, 4 });
+    comptime S.doTheTest(&[_]u8{ 1, 2, 3, 4 });
+}

test/stage1/behavior/if.zig

@@ -1,4 +1,6 @@
-const expect = @import("std").testing.expect;
+const std = @import("std");
+const expect = std.testing.expect;
+const expectEqual = std.testing.expectEqual;
 
 test "if statements" {
     shouldBeEqual(1, 1);
@@ -90,3 +92,18 @@ test "if prongs cast to expected type instead of peer type resolution" {
     S.doTheTest(false);
     comptime S.doTheTest(false);
 }
+
+test "while copies its payload" {
+    const S = struct {
+        fn doTheTest() void {
+            var tmp: ?i32 = 10;
+            if (tmp) |value| {
+                // Modify the original variable
+                tmp = null;
+                expectEqual(@as(i32, 10), value);
+            } else unreachable;
+        }
+    };
+    S.doTheTest();
+    comptime S.doTheTest();
+}

test/stage1/behavior/switch.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 const expect = std.testing.expect;
 const expectError = std.testing.expectError;
+const expectEqual = std.testing.expectEqual;
 
 test "switch with numbers" {
     testSwitchWithNumbers(13);
@@ -493,3 +494,24 @@ test "switch on error set with single else" {
     S.doTheTest();
     comptime S.doTheTest();
 }
+
+test "while copies its payload" {
+    const S = struct {
+        fn doTheTest() void {
+            var tmp: union(enum) {
+                A: u8,
+                B: u32,
+            } = .{ .A = 42 };
+            switch (tmp) {
+                .A => |value| {
+                    // Modify the original union
+                    tmp = .{ .B = 0x10101010 };
+                    expectEqual(@as(u8, 42), value);
+                },
+                else => unreachable,
+            }
+        }
+    };
+    S.doTheTest();
+    comptime S.doTheTest();
+}

test/stage1/behavior/while.zig

@@ -1,4 +1,5 @@
-const expect = @import("std").testing.expect;
+const std = @import("std");
+const expect = std.testing.expect;
 
 test "while loop" {
     var i: i32 = 0;
@@ -271,3 +272,18 @@ test "while error 2 break statements and an else" {
     S.entry(true, false);
     comptime S.entry(true, false);
 }
+
+test "while copies its payload" {
+    const S = struct {
+        fn doTheTest() void {
+            var tmp: ?i32 = 10;
+            while (tmp) |value| {
+                // Modify the original variable
+                tmp = null;
+                expect(value == 10);
+            }
+        }
+    };
+    S.doTheTest();
+    comptime S.doTheTest();
+}