Swift: Move logic into Ssa::WriteDefinition.assigns.

Author: geoffw0

swift/ql/lib/codeql/swift/dataflow/Ssa.qll

@@ -165,6 +165,14 @@ module Ssa {
         // TODO: We should probably enumerate more cfg nodes here.
         value.(PropertyGetterCfgNode).getRef() = init
       )
+      or
+      exists(VarDecl var, SsaInput::BasicBlock bb, int blockIndex, ConditionElement ce, Expr init |
+        this.definesAt(var, bb, blockIndex) and
+        ce.getPattern() = bb.getNode(blockIndex).getNode().asAstNode() and
+        init = ce.getInitializer()
+      |
+        value.getNode().asAstNode() = init
+      )
     }
   }
 

swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll

@@ -119,13 +119,6 @@ private module Cached {
       def.(Ssa::WriteDefinition).assigns(nodeFrom.getCfgNode()) and
       nodeTo.asDefinition() = def
       or
-      // flow through optional binding `if let`, similarly to assignment
-      exists(ConditionElement ce |
-        ce.getInitializer() = nodeFrom.asExpr() and
-        ce.getPattern() = def.getSourceVariable().getParentPattern() and
-        nodeTo.asDefinition() = def
-      )
-      or
       // step from def to first read
       nodeFrom.asDefinition() = def and
       nodeTo.getCfgNode() = def.getAFirstRead() and