fixes #15147 (#15315)

compiler/varpartitions.nim

@@ -396,7 +396,7 @@ proc deps(c: var Partitions; dest, src: PNode) =
             (src.sym.kind in {skLet, skParam, skForVar} and hasDisabledAsgn(src.sym.typ))):
           c.s[vid].flags.incl preventCursor
 
-    if hasDestructor(src.typ):
+    if src.kind == nkSym and hasDestructor(src.typ):
       rhsIsSink(c, src)
 
 proc traverse(c: var Partitions; n: PNode) =

tests/arc/topt_no_cursor.nim

@@ -171,3 +171,24 @@ proc encodedQuery =
     elem.tt()
 
 encodedQuery()
+
+# bug #15147
+
+proc s(input: string): (string, string) =
+  result = (";", "")
+
+proc charmatch(input: string): (string, string) =
+  result = ("123", input[0 .. input.high])
+
+proc plus(input: string) =
+  var
+    lvalue, rvalue: string # cursors
+    lnext: string # must be cursor!!!
+    rnext: string # cursor
+  let lresult = charmatch(input)
+  (lvalue, lnext) = lresult
+
+  let rresult = s(lnext)
+  (rvalue, rnext) = rresult
+
+plus("123;")