docs: mark issues 7, 8, 14 as fixed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ISSUES.md

@@ -123,45 +123,29 @@ List.map(items, addOne)
 
 ## Issue 7: Effectful callbacks in `List.map`/`forEach`/`fold`
 
-**Category**: Type checker limitation
+**Category**: Type checker limitation → **Fixed**
 **Severity**: Medium
 
 The type checker requires pure callbacks for higher-order List functions, but effectful callbacks are often needed (e.g., reading files in a map operation).
 
-**Reproduction**:
-```lux
-fn readFile(path: String): String with {File} = File.read(path)
-let contents = List.map(paths, fn(p: String): String => readFile(p));
-// ERROR: Effect mismatch: expected {File}, got {}
-```
-
-**Workaround**: Use manual recursion instead of List.map/forEach:
-```lux
-fn mapRead(paths: List<String>): List<String> with {File} =
-    match List.head(paths) {
-        None => [],
-        Some(p) => {
-            let content = readFile(p);
-            match List.tail(paths) {
-                Some(rest) => List.concat([content], mapRead(rest)),
-                None => [content]
-            }
-        }
-    }
-```
+**Fix**: Added effect propagation in `src/typechecker.rs`: callback arguments with effect annotations now propagate their effects to the enclosing function's inferred effect set, in `infer_call`, `infer_effect_op` (module access path), and `infer_effect_op` (effect op path).
 
 ---
 
-## Issue 8: `String.indexOf` and `String.lastIndexOf` missing from type checker
+## Issue 8: `String.indexOf` and `String.lastIndexOf` broken in C backend
 
-**Category**: Type checker gap → **Fixed**
+**Category**: C backend bug → **Fixed**
 **Severity**: Medium
 
-These functions exist in the interpreter but were not registered in the type checker, causing "Module 'String' has no member" errors.
+Type registrations were added previously, but C compilation of code using `String.indexOf`/`lastIndexOf` failed with type errors. Three root causes:
+1. Global `let` bindings always declared as `static LuxInt` regardless of value type
+2. `Option<Int>` inner type not tracked through function parameters, causing match extraction to default to `LuxString`
+3. `indexOf`/`lastIndexOf` stored ints as `(void*)(intptr_t)` but extraction expected boxed pointers (inconsistent with `parseInt`)
 
-**Fix**: Added type registrations in src/types.rs:
-- `String.indexOf(String, String) -> Option<Int>`
-- `String.lastIndexOf(String, String) -> Option<Int>`
+**Fix**: Fixed in `src/codegen/c_backend.rs`:
+- `emit_global_let` now infers type from value expression
+- Added `var_option_inner_types` map; function params with `Option<T>` annotations are tracked
+- `indexOf`/`lastIndexOf` now use `lux_box_int` consistently; extraction dereferences via `*(LuxInt*)`
 
 ---
 
@@ -243,12 +227,10 @@ let json = match Json.parse(raw) { Ok(j) => j, Err(_) => ... };
 
 ## Issue 14: No `File.copy`
 
-**Category**: Missing feature
+**Category**: Missing feature → **Fixed**
 **Severity**: Low
 
-Must shell out to copy files/directories.
-
-**Workaround**: `Process.exec("cp -r static/* _site/")`.
+**Fix**: Added `File.copy(source, dest)` to types.rs, interpreter.rs (using `std::fs::copy`), and C backend (fread/fwrite buffer copy).
 
 ---
 
@@ -273,12 +255,12 @@ Must manually scan directories and filter by extension.
 | 4 | Tuple field access `.0` `.1` | High | Open |
 | 5 | Multi-line function arguments | High | Open |
 | 6 | Multi-line lambdas in calls | High | Open |
-| 7 | Effectful callbacks in List HOFs | Medium | Open |
-| 8 | String.indexOf/lastIndexOf types | Medium | **Fixed** |
+| 7 | Effectful callbacks in List HOFs | Medium | **Fixed** |
+| 8 | String.indexOf/lastIndexOf C backend | Medium | **Fixed** |
 | 9 | No List.sort | Medium | Open |
 | 10 | No HashMap/Map | Medium | Open |
 | 11 | No regex | Medium | Open |
 | 12 | No multiline strings | Medium | Open |
 | 13 | Json.parse return type docs | Low | Open |
-| 14 | No File.copy | Low | Open |
+| 14 | No File.copy | Low | **Fixed** |
 | 15 | No file globbing | Low | Open |