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w6c+wcc/check: infer [_]T array length from initializer element count (fix #7)

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`[_]T = [...]` (canonical Hare array-length inference) silently
miscompiled to a zero-length array: the parser already left the array
type's length child nil as the infer sentinel — distinct from an
explicit [N] — but neither checker stamped the real count, so `len(x)`
returned 0 with no diagnostic (rule-7 silent miscompile). Module-level
was worse on wwstage, where `x.len` on ANY global array (even an
explicit [N]) fell to the SB fallback and mis-emitted `MOVQ len(SB), AX`
(linker: undefined reference to len).

The length lives in the stamped TYPE and cgen already keys stride /
length / data-emission off it, so stamping the inferred count at the one
checker inference point closes it permanently (rob's #7 ruling):

  - check.c clet + module-level N_LET pass-2: count the initializer's
    elements and patch the array type's length (the Sym too, so a later
    x.len reads the inferred alen). No-init / non-array init can't infer
    -> loud error, never a silent zero-length array.
  - check.ww inferarraylen: the wwstage twin — stamp a synthesized
    N_INTLIT length child before resolvewalk caches the array tinfo;
    same loud-error rule. Idempotent for the module-level double-call.
  - cgenexpr.ww cgdot: the missing wwstage arm for a top-level [N]T
    global's .len / .ptr (cstage cgen.c:8011 already had it).
  - cgenutil.ww letslotsize: drop the now-redundant [_] slot-size
    intercept — a workaround for this very bug; the stamped length flows
    through the general slotsize path (rule 7).

Both stages converge byte-identical; new table-driven test 684 covers
[_]int/[_]str/[_]u8 local + module-level, len + element read-back,
dual-stage runtime + asm byte-id, plus three negative no-infer rows.
This commit is contained in:
Hojun-Cho
2026-06-03 18:44:39 +09:00
parent 63cb39e45b
commit 7ca32432b1
8 changed files with 653 additions and 136 deletions
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7
Makefile
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@@ -241,6 +241,7 @@ TESTS = $(BIN)/test_smoke $(BIN)/test_lex $(BIN)/test_parse $(BIN)/test_check \
$(BIN)/test_arr_elem_field_write \
$(BIN)/test_arr_enum_elem \
$(BIN)/test_arr_strslice_elem \
$(BIN)/test_arr_infer_len \
$(BIN)/test_dot_str_chained_arg \
$(BIN)/test_dot_slice_arg \
$(BIN)/test_dot_tagged_source \
@@ -561,6 +562,12 @@ $(BIN)/test_arr_strslice_elem: test/wcc/683_arr_strslice_elem.c $(BIN)/ww \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_arr_infer_len: test/wcc/684_arr_infer_len.c $(BIN)/ww \
$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \
$(LIB)/libwwrt.a | $(BIN)
$(CC) $(CFLAGS) -o $@ $<
$(BIN)/test_dot_str_chained_arg: test/wcc/692_dot_str_chained_arg.c $(BIN)/ww \
$(BIN)/w6c $(BIN)/w6a $(BIN)/w6l \
$(BIN)/ww_ww $(BIN)/w6c_ww $(BIN)/w6a_ww $(BIN)/w6l_ww \