cursor and mutation tracking fixes (#15113)

* fixes #15110
* fixes #15096

* prepare varpartitions for cursor inference
* new cursor inference begins to work
* make tests green

compiler/ast.nim

@@ -1841,6 +1841,11 @@ proc isImportedException*(t: PType; conf: ConfigRef): bool =
 proc isInfixAs*(n: PNode): bool =
   return n.kind == nkInfix and n[0].kind == nkIdent and n[0].ident.s == "as"
 
+proc skipColon*(n: PNode): PNode =
+  result = n
+  if n.kind == nkExprColonExpr:
+    result = n[1]
+
 proc findUnresolvedStatic*(n: PNode): PNode =
   # n.typ == nil: see issue #14802
   if n.kind == nkSym and n.typ != nil and n.typ.kind == tyStatic and n.typ.n == nil:
@@ -1860,6 +1865,10 @@ when false:
       if n[i].containsNil: return true
 
 template hasDestructor*(t: PType): bool = {tfHasAsgn, tfHasOwned} * t.flags != {}
+
+proc hasDisabledAsgn*(t: PType): bool =
+  t.attachedOps[attachedAsgn] != nil and sfError in t.attachedOps[attachedAsgn].flags
+
 template incompleteType*(t: PType): bool =
   t.sym != nil and {sfForward, sfNoForward} * t.sym.flags == {sfForward}
 

compiler/injectdestructors.nim

@@ -17,7 +17,7 @@ import
   intsets, strtabs, ast, astalgo, msgs, renderer, magicsys, types, idents,
   strutils, options, dfa, lowerings, tables, modulegraphs, msgs,
   lineinfos, parampatterns, sighashes, liftdestructors, optimizer,
-  cursor_inference
+  varpartitions
 
 from trees import exprStructuralEquivalent, getRoot
 
@@ -1002,7 +1002,7 @@ proc injectDestructorCalls*(g: ModuleGraph; owner: PSym; n: PNode): PNode =
     echoCfg(c.g)
     echo n
 
-  computeCursors(n, g.config)
+  computeCursors(owner, n, g.config)
 
   var scope: Scope
   let body = p(n, c, scope, normal)

compiler/sempass2.nim

@@ -826,6 +826,8 @@ proc trackCall(tracked: PEffects; n: PNode) =
       case op[i].kind
       of tySink:
         checkForSink(tracked.config, tracked.owner, n[i])
+      of tyVar:
+        tracked.hasDangerousAssign = true
       #of tyOut:
       # consider this case: p(out x, x); we want to remark that 'x' is not
       # initialized until after the call. Since we do this after we analysed the