Structs, arrays, owned strings, memory model, modules, debug info

- struct with default values; constructors Point(1, 2) / Point(x: 1); field access, auto-deref through pointers
- []T arrays with bounds checks, literals, for-each, push/pop/insert/remove/clear/resize/find/contains/join/slice/reverse/sort
- str carries its length: .len, s[i], +, comparison, sub/find/split/trim/upper/lower/replace/repeat/bytes, str(x), int(s), float(s)
- Memory: values own their memory and are freed at the end of their block; assignment copies, temporaries move;
  parameters are lent and only copied when the function changes them; defer; new()/free() for manual heap memory
- input(), read_file/write_file/file_exists, exit(), fn main([]str args)
- Finch modules: import name, module.fn(), module.Struct
- C structs from headers (fields, fixed arrays, nested); passed and returned by value with the System V x86-64 ABI;
  addr(fn) gives C a callback
- link "file.c" compiles and links your own C code
- -g emits DWARF debug info (gdb/lldb)
- Small C runtime (runtime/finch_rt.c) embedded in the compiler, cached in ~/.cache/finch
- Tests: 58, all clean under valgrind (MEMCHECK=1 tests/run.sh)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/fail/array_compare.fn

@@ -0,0 +1,4 @@
+// expect: compare the parts one by one
+fn main() {
+    print([1] == [1])
+}

tests/fail/bad_int.fn

@@ -0,0 +1,4 @@
+// expect: can't turn "12x" into int
+fn main() {
+    print(int("12x"))
+}

tests/fail/defer_return.fn

@@ -0,0 +1,4 @@
+// expect: return can't be used inside defer
+fn main() {
+    defer return
+}

tests/fail/each_readonly.fn

@@ -0,0 +1,6 @@
+// expect: the loop variable 'x' can't be changed
+fn main() {
+    for x in [1, 2] {
+        x = 3
+    }
+}

tests/fail/empty_array.fn

@@ -0,0 +1,4 @@
+// expect: an empty [] needs a type
+fn main() {
+    a := []
+}

tests/fail/free_value.fn

@@ -0,0 +1,5 @@
+// expect: arrays, str and structs are freed by Finch
+fn main() {
+    x := 5
+    free(x)
+}

tests/fail/index_range.fn

@@ -0,0 +1,5 @@
+// expect: runtime error: index 5 is out of range (the length is 3)
+fn main() {
+    a := [1, 2, 3]
+    print(a[5])
+}

tests/fail/module_missing.fn

@@ -0,0 +1,3 @@
+// expect: can't find the module 'nothere'
+import nothere
+fn main() {}

tests/fail/module_not_imported.fn

@@ -0,0 +1,4 @@
+// expect: to use a module, add  import geometry
+fn main() {
+    v := geometry.Vec(1, 2)
+}

tests/fail/pop_empty.fn

@@ -0,0 +1,5 @@
+// expect: runtime error: pop() on an empty array
+fn main() {
+    []int a
+    a.pop()
+}

tests/fail/push_type.fn

@@ -0,0 +1,5 @@
+// expect: the element must be int, but this is str
+fn main() {
+    a := [1, 2]
+    a.push("x")
+}

tests/fail/str_null.fn

@@ -0,0 +1,6 @@
+// expect: a str is never null
+fn main() {
+    s := "a"
+    if s == null {
+    }
+}

tests/fail/str_plus_int.fn

@@ -0,0 +1,4 @@
+// expect: turn the other side into text first: str(...)
+fn main() {
+    s := "a" + 5
+}

tests/fail/struct_count.fn

@@ -0,0 +1,8 @@
+// expect: P has 2 fields, but got 1 values
+struct P {
+    int x
+    int y
+}
+fn main() {
+    p := P(1)
+}

tests/fail/struct_no_field.fn

@@ -0,0 +1,8 @@
+// expect: the struct P has no field 'y' (it has: x)
+struct P {
+    int x
+}
+fn main() {
+    p := P(1)
+    print(p.y)
+}

tests/fail/struct_self.fn

@@ -0,0 +1,5 @@
+// expect: contains itself; use ptr[A] or []A
+struct A {
+    A inner
+}
+fn main() {}