From fa66510f7a66f53c229d29728c9e76ba4ada5a0b Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Fri, 10 Jul 2026 14:07:35 +0200
Subject: [PATCH] IC: bugfix (#25982)

---
 compiler/sem.nim         |  8 ++++++++
 koch.nim                 |  2 +-
 tests/ic/mtraitparam.nim | 34 ++++++++++++++++++++++++++++++++++
 tests/ic/ttraitparam.nim | 14 ++++++++++++++
 4 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 tests/ic/mtraitparam.nim
 create mode 100644 tests/ic/ttraitparam.nim

diff --git a/compiler/sem.nim b/compiler/sem.nim
index ab6542f9d6..a689e2626f 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -288,6 +288,14 @@ proc newSymG*(kind: TSymKind, n: PNode, c: PContext): PSym =
         result = copySym(result)
         result.ast = n.sym.ast
         put(c.p, n.sym, result)
+    if result.state == Sealed:
+      # the symbol was loaded from another module's NIF cache (e.g. a param
+      # symbol spliced out of an imported proc type by a `typed` macro) and is
+      # therefore immutable; the caller re-owns it and assigns its type/flags,
+      # so hand back a fresh, mutable copy owned by the current module instead.
+      let fresh = copySym(result, c.idgen)
+      fresh.ast = result.ast
+      result = fresh
     # when there is a nested proc inside a template, semtmpl
     # will assign a wrong owner during the first pass over the
     # template; we must fix it here: see #909
diff --git a/koch.nim b/koch.nim
index 9d63618e67..1220550681 100644
--- a/koch.nim
+++ b/koch.nim
@@ -619,7 +619,7 @@ proc runIcTestFile(inp: string) =
 const icSuite = ["thallo", "tconverter", "timp", "tmiscs", "tparseutils",
                  "tcompiletimeglobal", "tsighashstable", "tpureenum", "tgenericoffer",
                  "tconverterreexport", "ttypeoffer", "ttransitiveoffer",
-                 "tmodsymref", "tmethupref", "temit"]
+                 "tmodsymref", "tmethupref", "temit", "ttraitparam"]
 
 proc icTest(args: string) =
   temp("")
diff --git a/tests/ic/mtraitparam.nim b/tests/ic/mtraitparam.nim
new file mode 100644
index 0000000000..b18fbb1e5f
--- /dev/null
+++ b/tests/ic/mtraitparam.nim
@@ -0,0 +1,34 @@
+import std/macros
+
+type
+  Chunk* = ref object
+    x*: int32
+  ChunkTrait* = distinct tuple[
+    loaded: proc(self: pointer, chunk: Chunk)
+  ]
+
+macro makeVTable*(traitType: typedesc): untyped =
+  ## Splice the param symbols out of an imported proc type into a fresh proc
+  ## type nested in a fresh tuple type. Under `nim ic` the imported trait is
+  ## loaded from a NIF cache, so its param symbols are `Sealed`; re-owning them
+  ## in `semProcTypeNode` used to trip `ast.nim` `s.state != Sealed`.
+  var t = traitType.getTypeInst[1].getTypeImpl
+  if t.kind == nnkDistinctTy: t = t[0]
+  let formalParams = t[0][1][0]
+  var bridgeParams = nnkFormalParams.newTree(formalParams[0].copyNimTree)
+  bridgeParams.add nnkIdentDefs.newTree(ident"p", ident"pointer", newEmptyNode())
+  for j in 2 ..< formalParams.len:
+    bridgeParams.add formalParams[j].copyNimTree
+  let vtType = nnkTupleTy.newTree(
+    nnkIdentDefs.newTree(ident"m0",
+      nnkProcTy.newTree(bridgeParams, nnkPragma.newTree(ident"nimcall")),
+      newEmptyNode()))
+  let vtName = genSym(nskType, "VT")
+  let vtVar = genSym(nskVar, "vt")
+  result = nnkStmtList.newTree(
+    nnkTypeSection.newTree(
+      nnkTypeDef.newTree(vtName, newEmptyNode(), vtType)),
+    nnkVarSection.newTree(
+      nnkIdentDefs.newTree(
+        nnkPragmaExpr.newTree(vtVar, nnkPragma.newTree(ident"used")),
+        vtName, newEmptyNode())))
diff --git a/tests/ic/ttraitparam.nim b/tests/ic/ttraitparam.nim
new file mode 100644
index 0000000000..35a81d39cb
--- /dev/null
+++ b/tests/ic/ttraitparam.nim
@@ -0,0 +1,14 @@
+discard """
+output: '''ok'''
+"""
+
+# Regression test: a `typed` macro in an imported module splices param symbols
+# out of an imported proc type into a freshly semchecked proc type. Under
+# `nim ic` those param symbols are loaded `Sealed` from the NIF cache; reusing
+# them in `newSymG`/`semProcTypeNode` used to fail `ast.nim` `s.state != Sealed`.
+
+import mtraitparam
+
+makeVTable(ChunkTrait)
+
+echo "ok"