decomp: say the FIX, not the diagnosis

The 64-bit failure now reported Hex-Rays verbatim — "only 64-bit functions can
be decompiled in the current database" — with the actionable half appended after
it. A status bar cuts off the end, so the user got a perfect description of their
problem and nothing about what to do, which is the same dead end as before with
extra words.

  before: sub_0: cannot decompile — only 64-bit functions can be decompiled in
          the current database — Ctrl+L and pick arm:ARMv7-A      (125 chars)
  after:  sub_0: cannot decompile — this database is 64-bit — Ctrl+L, pick
          arm:ARMv7-A                                              (76 chars)

For this one failure the instruction IS the whole message: it can't be fixed in
place (bitness is decided at load), so describing the database serves nobody.
Other Hex-Rays reasons still pass through verbatim — they're usually about the
function, and there the description is the useful part.

Verified the whole path in a live pane on experiments/fibonacci.bin: the load
dialog now shows arm vs arm:ARMv7-A/M/v6-M/v5TE with their bitness spelled out,
picking arm:ARMv7-A gives 54 functions, and sub_0 decompiles:

  void __fastcall __noreturn sub_0(int a1) { ... v2 = sub_E3C(a1, 0); ... }

tests: thumb (16) now asserts the message names the fix rather than quoting
Hex-Rays, and that it fits under 110 chars — the truncation is what made the
last version useless, so it's worth a check. 209/0 scenarios, 30/0 blob.

2 files changed, 16 insertions, 4 deletions

diff --git a/idatui/domain.py b/idatui/domain.py
index a92ea49..084312a 100644
--- a/idatui/domain.py
+++ b/idatui/domain.py
@@ -1383,8 +1383,14 @@ class Program:
             return ""
         reason = str(r.get("reason") or "")
         if reason and r.get("bitness") == 64 and "64-bit" in reason:
-            # Unfixable in place: the database's bitness is decided at load.
-            reason += " \u2014 Ctrl+L and pick arm:ARMv7-A"
+            # Say the FIX, not the diagnosis. Hex-Rays' own sentence ("only
+            # 64-bit functions can be decompiled in the current database") is
+            # accurate and useless: it describes the database, not what to do,
+            # and it's long enough that a status bar cuts off the end — which is
+            # exactly where an appended hint would live. This is unfixable in
+            # place (bitness is decided at load), so the whole message is the
+            # instruction.
+            return "this database is 64-bit \u2014 Ctrl+L, pick arm:ARMv7-A"
         return reason
 
     def set_thumb(self, ea: int, mode: str = "toggle") -> dict:
diff --git a/tests/test_thumb_ui.py b/tests/test_thumb_ui.py
index 5b6f18e..84afcaf 100644
--- a/tests/test_thumb_ui.py
+++ b/tests/test_thumb_ui.py
@@ -161,10 +161,16 @@ async def run() -> int:
         await wait(lambda: "cannot decompile" in
                    str(app.query_one("#status", Static).render()), pilot, 90)
         status = str(app.query_one("#status", Static).render())
-        check("a failed decompile says why, in Hex-Rays' own words",
-              "only 64-bit functions" in status, status[:130])
+        # The message must say what to DO. Hex-Rays' own sentence ("only 64-bit
+        # functions can be decompiled in the current database") describes the
+        # database, not the fix, and is long enough that a status bar cuts off
+        # the end — which is where an appended hint would have lived.
+        check("a failed decompile names the fix, not just the diagnosis",
+              "Ctrl+L" in status and "ARMv7-A" in status, status[:130])
         check("and the reason survives the view reloading under it",
               "cannot decompile" in status, status[:130])
+        check("the message fits a narrow status bar",
+              len(status) < 110, f"{len(status)} chars: {status[:130]}")
 
     # -- the whole point: a 32-bit database decompiles ---------------------- #
     for ext in (".i64", ".id0", ".id1", ".id2", ".nam", ".til"):