fix(sem): noreturn analysis for void exprs

Summary
=======

`void` branches preceeding with no-return terminal branches are checked
with no-return analysis to avoid false positives.

Details
=====

The analysis is updated to recursively check `if/elif/of/except`
non-terminal branches as well as the terminal branch.

compiler/ast/ast_query.nim

@@ -695,22 +695,23 @@ proc endsInNoReturn*(n: PNode): bool =
   ## etc.) or a call of a noreturn proc. This is meant to be called on a
   ## semmed `n`.
   var it = n
-  while it.kind in {nkStmtList, nkStmtListExpr} and it.len > 0 or
+  while it.kind in {nkStmtList, nkStmtListExpr, nkElifBranch, nkElse, nkOfBranch, nkExceptBranch} and it.len > 0 or
         it.kind in {nkIfStmt, nkCaseStmt, nkBlockStmt, nkTryStmt} and it.typ.isEmptyType:
     case it.kind
-    of nkStmtList, nkStmtListExpr, nkBlockStmt:
+    of nkStmtList, nkStmtListExpr, nkBlockStmt, nkOfBranch, nkElifBranch, nkElse, nkExceptBranch:
       it = it.lastSon
     of nkIfStmt, nkCaseStmt:
-      it = it.lastSon.lastSon
+      # look through all but the last branch, which is covered after the loop
+      for i in 0..<(it.len - 1):
+        if not endsInNoReturn(it[i]):
+          return false
+      it = it.lastSon
     of nkTryStmt:
-      it =
-        case it[^1].kind
-        of nkFinally:
-          it[^2]
-        of nkExceptBranch:
-          it[^1]
-        of nkAllNodeKinds - {nkFinally, nkExceptBranch}:
-          unreachable()
+      # look through all but the last branch, which is covered after the loop
+      for i in 0..<(it.len - ord(it[^1].kind == nkFinally)):
+        if not endsInNoReturn(it[i]):
+          return false
+      it = it.lastSon
     else:
       unreachable()
   result = it.kind in nkLastBlockStmts or

tests/lang_exprs/tnoreturn_nested_reject_void.nim

@@ -0,0 +1,16 @@
+discard """
+  description: '''
+    Ensure nested non-noreturn statements aren't treated as such
+  '''
+  errormsg: "expression '1' is of type 'int literal(1)' and has to be used (or discarded)"
+  line: 11
+"""
+
+let x =
+  if true:
+    1
+  else:
+    if true:
+      echo "fun" # void
+    else:
+      raise newException(Defect, "gone") # no return