PS: Fix two bad joins.

Author: MathiasVP

powershell/ql/lib/semmle/code/powershell/controlflow/CfgNodes.qll

@@ -62,6 +62,9 @@ class StmtCfgNode extends AstCfgNode {
   Stmt getStmt() { result = s }
 }
 
+pragma[nomagic]
+private BasicBlock getARelevantBasicBlock(Ast a) { result.getANode().getAstNode() = a }
+
 /**
  * A class for mapping parent-child AST nodes to parent-child CFG nodes.
  */
@@ -86,7 +89,7 @@ abstract private class ChildMapping extends Ast {
     or
     exists(BasicBlock mid |
       this.reachesBasicBlock(child, cfn, mid) and
-      not mid.getANode().getAstNode() = child
+      not mid = getARelevantBasicBlock(child)
     |
       if this.precedesParent(child) then bb = mid.getAPredecessor() else bb = mid.getASuccessor()
     )

powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll

@@ -1083,11 +1083,8 @@ predicate readStep(Node node1, ContentSet c, Node node2) {
   )
   or
   // Read from a collection into a `foreach` loop
-  exists(
-    CfgNodes::StmtNodes::ForEachStmtCfgNode forEach, Content::KnownElementContent ec, BasicBlock bb,
-    int i
-  |
-    c.isKnownOrUnknownElement(ec) and
+  c.isAnyPositional() and
+  exists(CfgNodes::StmtNodes::ForEachStmtCfgNode forEach, BasicBlock bb, int i |
     node1.asExpr() = forEach.getIterableExpr() and
     bb.getNode(i) = forEach.getVarAccess() and
     node2.asDefinition().definesAt(_, bb, i)