fixes #26119; stack usage increase on try/except expression (#26166)

fixes #26119

compiler/injectdestructors.nim

@@ -787,6 +787,12 @@ template handleNestedTempl(n, processCall: untyped, willProduceStmt = false,
     result = nil
     assert(false)
 
+  if willProduceStmt:
+    # The value is now produced by statements in the branches. Keeping the
+    # control-flow node's expression type would make code generators allocate
+    # a second, unused destination for it.
+    result.typ = nil
+
 proc pRaiseStmt(n: PNode, c: var Con; s: var Scope): PNode =
   if optOwnedRefs in c.graph.config.globalOptions and n[0].kind != nkEmpty:
     if n[0].kind in nkCallKinds:

tests/ccgbugs/t26119.nim

@@ -0,0 +1,20 @@
+discard """
+  targets: "c cpp"
+  matrix: "--mm:refc; --mm:orc"
+  ccodeCheck: "\\i !@('W T' \\d+ '_;')"
+"""
+
+type W {.exportc.} = object
+  data: array[1000, byte]
+  items: seq[int]
+
+# bug #26119: assigning a try expression directly to the result must not leave
+# an unused temporary of the result type in the generated procedure.
+proc y(): W {.exportc.} =
+  try:
+    default(W)
+  except CatchableError:
+    default(W)
+
+var v = y()
+doAssert v.data[0] == 0 and v.items.len == 0