PS: Flow through conversions.

Author: MathiasVP

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

@@ -102,6 +102,8 @@ module LocalFlow {
     or
     nodeFrom.asExpr() = nodeTo.asStmt().(CfgNodes::StmtNodes::CmdExprCfgNode).getExpr()
     or
+    nodeFrom.asExpr() = nodeTo.asExpr().(CfgNodes::ExprNodes::ConvertCfgNode).getBase()
+    or
     exists(
       CfgNodes::ExprNodes::ArrayExprCfgNode arrayExpr, EscapeContainer::EscapeContainer container
     |

powershell/ql/test/library-tests/dataflow/local/test.expected

@@ -20,6 +20,7 @@
 | test.ps1:10:6:10:16 | [...]... | test.ps1:10:1:10:3 | c |
 | test.ps1:10:6:10:16 | [...]... | test.ps1:10:1:10:16 | ...=... |
 | test.ps1:10:6:10:16 | [...]... | test.ps1:10:6:10:16 | [...]... |
+| test.ps1:10:14:10:16 | b | test.ps1:10:6:10:16 | [...]... |
 | test.ps1:11:1:11:8 | Sink | test.ps1:11:1:11:8 | pre-return value for Sink |
 | test.ps1:11:1:11:8 | Sink | test.ps1:11:1:11:8 | pre-return value for Sink |
 | test.ps1:11:1:11:8 | implicit unwrapping of Sink | test.ps1:1:1:11:8 | return value for test.ps1 |