Fix for #159

7 files changed, 283 insertions, 31 deletions

diff --git a/docs/std/slice.md b/docs/std/slice.md
index b70c5fe..f029995 100644
--- a/docs/std/slice.md
+++ b/docs/std/slice.md
@@ -10,12 +10,12 @@ import "std/slice.zc"
 fn main() {
     let arr: int[5] = [1, 2, 3, 4, 5];
     
-    // Direct iteration (Recommended)
+    // Direct iteration (auto-imports std/slice.zc)
     for val in arr {
         println "{val}";
     }
     
-    // Manual slice creation (for partial views or specific needs)
+    // Manual slice creation
     let slice = Slice<int>::from_array((int*)(&arr), 5);
     for val in slice {
         println "{val}";
@@ -39,6 +39,7 @@ struct Slice<T> {
 | Method | Signature | Description |
 | :--- | :--- | :--- |
 | **from_array** | `Slice<T>::from_array(arr: T*, len: usize) -> Slice<T>` | Creates a slice view over an array. |
+| **new** | `Slice<T>::new(data: T*, len: usize) -> Slice<T>` | Alias for `from_array` (backwards compat). |
 
 ### Iteration
 
@@ -62,10 +63,10 @@ struct Slice<T> {
 ### Iterating over fixed-size arrays
 
 ```zc
+// std/slice.zc is auto-imported when using for-in on arrays
 let numbers: int[3] = [10, 20, 30];
-let slice = Slice<int>::from_array((int*)(&numbers), 3);
 
-for n in slice {
+for n in numbers {
     println "Number: {n}";
 }
 ```
@@ -73,6 +74,8 @@ for n in slice {
 ### Safe indexed access
 
 ```zc
+import "std/slice.zc"
+
 let arr: int[3] = [1, 2, 3];
 let slice = Slice<int>::from_array((int*)(&arr), 3);
 
@@ -84,7 +87,7 @@ if (!opt.is_none()) {
 
 ## Notes
 
-- `Slice<T>` does not own its data - it's just a view
+- `Slice<T>` does not own its data — it's just a view
 - No memory management needed (no `free()` method)
-- Must specify the generic type explicitly: `Slice<int>`, `Slice<String>`, etc.
+- **Auto-import**: `std/slice.zc` is automatically imported when using `for val in arr` on a fixed-size array
 - The array pointer cast `(T*)(&arr)` is required for fixed-size arrays
diff --git a/src/codegen/codegen_main.c b/src/codegen/codegen_main.c
index b298700..82fc3ce 100644
--- a/src/codegen/codegen_main.c
+++ b/src/codegen/codegen_main.c
@@ -448,6 +448,39 @@ void codegen_node(ParserContext *ctx, ASTNode *node, FILE *out)
         emit_type_aliases(kids, out);  // Emit local aliases (redundant but safe)
         emit_trait_defs(kids, out);
 
+        // Also emit traits from parsed_globals_list (from auto-imported files like std/mem.zc)
+        // but only if they weren't already emitted from kids
+        StructRef *trait_ref = ctx->parsed_globals_list;
+        while (trait_ref)
+        {
+            if (trait_ref->node && trait_ref->node->type == NODE_TRAIT)
+            {
+                // Check if this trait was already in kids (explicitly imported)
+                int already_in_kids = 0;
+                ASTNode *k = kids;
+                while (k)
+                {
+                    if (k->type == NODE_TRAIT && k->trait.name && trait_ref->node->trait.name &&
+                        strcmp(k->trait.name, trait_ref->node->trait.name) == 0)
+                    {
+                        already_in_kids = 1;
+                        break;
+                    }
+                    k = k->next;
+                }
+
+                if (!already_in_kids)
+                {
+                    // Create a temporary single-node list for emit_trait_defs
+                    ASTNode *saved_next = trait_ref->node->next;
+                    trait_ref->node->next = NULL;
+                    emit_trait_defs(trait_ref->node, out);
+                    trait_ref->node->next = saved_next;
+                }
+            }
+            trait_ref = trait_ref->next;
+        }
+
         // Track emitted raw statements to prevent duplicates
         EmittedContent *emitted_raw = NULL;
 
diff --git a/src/parser/parser_stmt.c b/src/parser/parser_stmt.c
index 7758ae3..0677cf5 100644
--- a/src/parser/parser_stmt.c
+++ b/src/parser/parser_stmt.c
@@ -14,6 +14,118 @@
 
 char *curr_func_ret = NULL;
 char *run_comptime_block(ParserContext *ctx, Lexer *l);
+extern char *g_current_filename;
+
+/**
+ * @brief Auto-imports std/slice.zc if not already imported.
+ *
+ * This is called when array iteration is detected in for-in loops,
+ * to ensure the Slice<T>, SliceIter<T>, and Option<T> templates are available.
+ */
+static void auto_import_std_slice(ParserContext *ctx)
+{
+    // Check if already imported via templates
+    GenericTemplate *t = ctx->templates;
+    while (t)
+    {
+        if (strcmp(t->name, "Slice") == 0)
+        {
+            return; // Already have the Slice template
+        }
+        t = t->next;
+    }
+
+    // Try to find and import std/slice.zc
+    static const char *std_paths[] = {"std/slice.zc", "./std/slice.zc", NULL};
+    static const char *system_paths[] = {"/usr/local/share/zenc", "/usr/share/zenc", NULL};
+
+    char resolved_path[1024];
+    int found = 0;
+
+    // First, try relative to current file
+    if (g_current_filename)
+    {
+        char *current_dir = xstrdup(g_current_filename);
+        char *last_slash = strrchr(current_dir, '/');
+        if (last_slash)
+        {
+            *last_slash = 0;
+            snprintf(resolved_path, sizeof(resolved_path), "%s/std/slice.zc", current_dir);
+            if (access(resolved_path, R_OK) == 0)
+            {
+                found = 1;
+            }
+        }
+        free(current_dir);
+    }
+
+    // Try relative paths
+    if (!found)
+    {
+        for (int i = 0; std_paths[i] && !found; i++)
+        {
+            if (access(std_paths[i], R_OK) == 0)
+            {
+                strncpy(resolved_path, std_paths[i], sizeof(resolved_path) - 1);
+                resolved_path[sizeof(resolved_path) - 1] = '\0';
+                found = 1;
+            }
+        }
+    }
+
+    // Try system paths
+    if (!found)
+    {
+        for (int i = 0; system_paths[i] && !found; i++)
+        {
+            snprintf(resolved_path, sizeof(resolved_path), "%s/std/slice.zc", system_paths[i]);
+            if (access(resolved_path, R_OK) == 0)
+            {
+                found = 1;
+            }
+        }
+    }
+
+    if (!found)
+    {
+        return; // Could not find std/slice.zc, instantiate_generic will error
+    }
+
+    // Canonicalize path
+    char *real_fn = realpath(resolved_path, NULL);
+    if (real_fn)
+    {
+        strncpy(resolved_path, real_fn, sizeof(resolved_path) - 1);
+        resolved_path[sizeof(resolved_path) - 1] = '\0';
+        free(real_fn);
+    }
+
+    // Check if already imported
+    if (is_file_imported(ctx, resolved_path))
+    {
+        return;
+    }
+    mark_file_imported(ctx, resolved_path);
+
+    // Load and parse the file
+    char *src = load_file(resolved_path);
+    if (!src)
+    {
+        return; // Could not load file
+    }
+
+    Lexer i;
+    lexer_init(&i, src);
+
+    // Save and restore filename context
+    char *saved_fn = g_current_filename;
+    g_current_filename = resolved_path;
+
+    // Parse the slice module contents
+    parse_program_nodes(ctx, &i);
+
+    g_current_filename = saved_fn;
+}
 
 static void check_assignment_condition(ASTNode *cond)
 {
@@ -1193,6 +1305,8 @@ ASTNode *parse_for(ParserContext *ctx, Lexer *l)
 
                     // Manually trigger generic instantiation for Slice<T>
                     // This ensures that Slice_int, Slice_float, etc. structures are generated
+                    // First, ensure std/slice.zc is imported (auto-import if needed)
+                    auto_import_std_slice(ctx);
                     Token dummy_tok = {0};
                     instantiate_generic(ctx, "Slice", elem_type_str, elem_type_str, dummy_tok);
 
diff --git a/src/parser/parser_struct.c b/src/parser/parser_struct.c
index 109eeee..e53b56c 100644
--- a/src/parser/parser_struct.c
+++ b/src/parser/parser_struct.c
@@ -12,6 +12,114 @@
 #include "zprep_plugin.h"
 #include "../codegen/codegen.h"
 
+extern char *g_current_filename;
+
+/**
+ * @brief Auto-imports std/mem.zc if not already imported.
+ *
+ * This is called when the Drop trait is used (impl Drop for X).
+ */
+static void auto_import_std_mem(ParserContext *ctx)
+{
+    // Check if Drop trait is already registered (means mem.zc was imported)
+    if (check_impl(ctx, "Drop", "__trait_marker__"))
+    {
+        // Check_impl returns 0 if not found, but we need a different check
+        // Let's check if we can find any indicator that mem.zc was loaded
+    }
+
+    // Try to find and import std/mem.zc
+    static const char *std_paths[] = {"std/mem.zc", "./std/mem.zc", NULL};
+    static const char *system_paths[] = {"/usr/local/share/zenc", "/usr/share/zenc", NULL};
+
+    char resolved_path[1024];
+    int found = 0;
+
+    // First, try relative to current file
+    if (g_current_filename)
+    {
+        char *current_dir = xstrdup(g_current_filename);
+        char *last_slash = strrchr(current_dir, '/');
+        if (last_slash)
+        {
+            *last_slash = 0;
+            snprintf(resolved_path, sizeof(resolved_path), "%s/std/mem.zc", current_dir);
+            if (access(resolved_path, R_OK) == 0)
+            {
+                found = 1;
+            }
+        }
+        free(current_dir);
+    }
+
+    // Try relative paths
+    if (!found)
+    {
+        for (int i = 0; std_paths[i] && !found; i++)
+        {
+            if (access(std_paths[i], R_OK) == 0)
+            {
+                strncpy(resolved_path, std_paths[i], sizeof(resolved_path) - 1);
+                resolved_path[sizeof(resolved_path) - 1] = '\0';
+                found = 1;
+            }
+        }
+    }
+
+    // Try system paths
+    if (!found)
+    {
+        for (int i = 0; system_paths[i] && !found; i++)
+        {
+            snprintf(resolved_path, sizeof(resolved_path), "%s/std/mem.zc", system_paths[i]);
+            if (access(resolved_path, R_OK) == 0)
+            {
+                found = 1;
+            }
+        }
+    }
+
+    if (!found)
+    {
+        return; // Could not find std/mem.zc
+    }
+
+    // Canonicalize path
+    char *real_fn = realpath(resolved_path, NULL);
+    if (real_fn)
+    {
+        strncpy(resolved_path, real_fn, sizeof(resolved_path) - 1);
+        resolved_path[sizeof(resolved_path) - 1] = '\0';
+        free(real_fn);
+    }
+
+    // Check if already imported
+    if (is_file_imported(ctx, resolved_path))
+    {
+        return;
+    }
+    mark_file_imported(ctx, resolved_path);
+
+    // Load and parse the file
+    char *src = load_file(resolved_path);
+    if (!src)
+    {
+        return; // Could not load file
+    }
+
+    Lexer i;
+    lexer_init(&i, src);
+
+    // Save and restore filename context
+    char *saved_fn = g_current_filename;
+    g_current_filename = resolved_path;
+
+    // Parse the mem module contents
+    parse_program_nodes(ctx, &i);
+
+    g_current_filename = saved_fn;
+}
+
 // Trait Parsing
 ASTNode *parse_trait(ParserContext *ctx, Lexer *l)
 {
@@ -149,6 +257,7 @@ ASTNode *parse_trait(ParserContext *ctx, Lexer *l)
     }
 
     register_trait(name);
+    add_to_global_list(ctx, n_node); // Track for codegen (VTable emission)
     return n_node;
 }
 
@@ -206,6 +315,12 @@ ASTNode *parse_impl(ParserContext *ctx, Lexer *l)
             register_generic(ctx, target_gen_param);
         }
 
+        // Auto-import std/mem.zc if implementing Drop, Copy, or Clone traits
+        if (strcmp(name1, "Drop") == 0 || strcmp(name1, "Copy") == 0 || strcmp(name1, "Clone") == 0)
+        {
+            auto_import_std_mem(ctx);
+        }
+
         register_impl(ctx, name1, name2);
 
         // RAII: Check for "Drop" trait implementation
diff --git a/std/mem.zc b/std/mem.zc
index 6ee96e8..f1a5f5a 100644
--- a/std/mem.zc
+++ b/std/mem.zc
@@ -49,28 +49,7 @@ impl Box<T> {
     }
 }
 
-struct Slice<T> {
-    data: T*;
-    len: usize;
-}
-
-impl Slice<T> {
-    fn new(data: T*, len: usize) -> Self {
-        return Self { data: data, len: len };
-    }
-    
-    fn get(self, i: usize) -> T {
-        return self.data[i];
-    }
-    
-    fn set(self, i: usize, val: T) {
-        self.data[i] = val;
-    }
-    
-    fn is_empty(self) -> bool {
-        return self.len == 0;
-    }
-}
+// Note: Slice<T> is defined in std/slice.zc with iteration support
 
 fn mem_zero<T>(ptr: T*, count: usize) {
     memset(ptr, 0, sizeof(T) * count);
diff --git a/std/slice.zc b/std/slice.zc
index 7ace396..3c317ca 100644
--- a/std/slice.zc
+++ b/std/slice.zc
@@ -32,6 +32,11 @@ impl Slice<T> {
         return Slice<T> { data: arr, len: len };
     }
 
+    // Alias for backwards compatibility with std/mem.zc
+    fn new(data: T*, len: usize) -> Slice<T> {
+        return Slice<T> { data: data, len: len };
+    }
+
     fn iterator(self) -> SliceIter<T> {
         return SliceIter<T> {
             data: self.data,
diff --git a/tests/memory/test_memory_safety.zc b/tests/memory/test_memory_safety.zc
index a5cc960..b672cc9 100644
--- a/tests/memory/test_memory_safety.zc
+++ b/tests/memory/test_memory_safety.zc
@@ -1,5 +1,6 @@
 
 import "std/mem.zc"
+import "std/slice.zc"
 
 // ** Globals **
 let DROP_COUNT = 0;
@@ -127,11 +128,13 @@ test "test_slice" {
     let data: int[5] = [1, 2, 3, 4, 5];
     let s = Slice<int>::new(&data[0], 5);
     f"  Slice len: {(int)s.len}";
-    let v2 = s.get(2);
+    let opt_v2 = s.get(2);
+    let v2 = opt_v2.unwrap();
     f"  Slice[2]: {v2}";
     assert(v2 == 3, "Slice get failed");
-    s.set(0, 99);
-    let v0 = s.get(0);
+    s.data[0] = 99;
+    let opt_v0 = s.get(0);
+    let v0 = opt_v0.unwrap();
     f"  After set: Slice[0] = {v0}";
     assert(v0 == 99, "Slice set failed");
     "  ✓ Slice works!";