From 1ebdcb3bcaac3259193de6f8ce1d94889c3dc100 Mon Sep 17 00:00:00 2001
From: metagn <metagngn@gmail.com>
Date: Tue, 3 Sep 2024 06:45:44 +0300
Subject: [PATCH] fully disable static paramTypesMatch for tyFromExpr in
 generics (#24049)

fixes #24044

When matching a `tyFromExpr` against a `static` generic parameter,
`paramTypesMatch` tries to evaluate it as a constant expression, which
causes a segfault in the case of #24044. In #24005 a consequence of the
same behavior was an issue where `nkStaticExpr` was created for
`tyFromExpr` which made it not instantiate, so only the generation of
`nkStaticExpr` was disabled. Instead we now just completely ignore
`tyFromExpr` matching a `static` generic parameter in generic contexts
and keep it untouched.
---
 compiler/sigmatch.nim                          | 9 ++++-----
 tests/generics/tuninstantiatedgenericcalls.nim | 8 ++++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index b7efa8e4511f9..c7a8c496cc927 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -2293,6 +2293,9 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
          a.n == nil and
          tfGenericTypeParam notin a.flags:
         return newNodeIT(nkType, argOrig.info, makeTypeFromExpr(c, arg))
+    elif a.kind == tyFromExpr and c.inGenericContext > 0:
+      # don't try to evaluate
+      discard
     elif arg.kind != nkEmpty:
       var evaluated = c.semTryConstExpr(c, arg)
       if evaluated != nil:
@@ -2305,11 +2308,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, a: PType,
         a = typ
       else:
         if m.callee.kind == tyGenericBody:
-          # we can't use `makeStaticExpr` if `arg` has a generic type
-          # because it generates `tyStatic`, which semtypinst doesn't touch
-          # not sure if checking for `tyFromExpr` is enough
-          if f.kind == tyStatic and typeRel(m, f.base, a) != isNone and
-              a.kind != tyFromExpr:
+          if f.kind == tyStatic and typeRel(m, f.base, a) != isNone:
             result = makeStaticExpr(m.c, arg)
             result.typ.flags.incl tfUnresolved
             result.typ.n = arg
diff --git a/tests/generics/tuninstantiatedgenericcalls.nim b/tests/generics/tuninstantiatedgenericcalls.nim
index b5be434aae3be..45de244597206 100644
--- a/tests/generics/tuninstantiatedgenericcalls.nim
+++ b/tests/generics/tuninstantiatedgenericcalls.nim
@@ -325,6 +325,14 @@ block: # issue #12714
     MyChannel[T: Enqueueable] = object
       dummy: type(default(T)[])
 
+block: # issue #24044
+  type ArrayBuf[N: static int, T = byte] = object
+    buf: array[N, T]
+  template maxLen(T: type): int =
+    sizeof(T) * 2
+  type MyBuf[I] = ArrayBuf[maxLen(I)]
+  var v: MyBuf[int]
+
 when false: # issue #22342, type section version of #22607
   type GenAlias[isInt: static bool] = (
     when isInt: