C backend: fix crash when number of Decls passes a threshold

The ensureUnusedCapacity did not reserve a big enough number. I changed
it to no longer guess the capacity because I saw that the number of
possible items was not determinable ahead of time and this can therefore
avoid allocating more memory than necessary.

1 files changed, 15 insertions, 0 deletions

diff --git a/test/behavior/if.zig b/test/behavior/if.zig
index a1f722d827..e907f288de 100644
--- a/test/behavior/if.zig
+++ b/test/behavior/if.zig
@@ -73,3 +73,18 @@ test "const result loc, runtime if cond, else unreachable" {
     const x = if (t) Num.Two else unreachable;
     try expect(x == .Two);
 }
+
+test "if copies its payload" {
+    const S = struct {
+        fn doTheTest() !void {
+            var tmp: ?i32 = 10;
+            if (tmp) |value| {
+                // Modify the original variable
+                tmp = null;
+                try expect(value == 10);
+            } else unreachable;
+        }
+    };
+    try S.doTheTest();
+    comptime try S.doTheTest();
+}