Swift: Add a closure flow step from the right-hand side of variable declarations to the underlying pattern.

Author: MathiasVP

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

@@ -151,7 +151,8 @@ private module Cached {
         [
           any(Argument arg | modifiable(arg)).getExpr(), any(MemberRefExpr ref).getBase(),
           any(ApplyExpr apply).getQualifier(), any(TupleElementExpr te).getSubExpr(),
-          any(SubscriptExpr se).getBase()
+          any(SubscriptExpr se).getBase(),
+          any(ApplyExpr apply | not exists(apply.getStaticTarget())).getFunction()
         ])
     } or
     TDictionarySubscriptNode(SubscriptExpr e) {
@@ -838,13 +839,15 @@ private predicate simpleAstFlowStep(Expr e1, Expr e2) {
   e2.(ArrayExpr).getAnElement() = e1
 }
 
-private predicate closureFlowStep(Expr e1, Expr e2) {
+private predicate closureFlowStep(CaptureInput::Expr e1, CaptureInput::Expr e2) {
   simpleAstFlowStep(e1, e2)
   or
   exists(Ssa::WriteDefinition def |
     def.getARead().getNode().asAstNode() = e2 and
     def.assigns(any(CfgNode cfg | cfg.getNode().asAstNode() = e1))
   )
+  or
+  e2.(Pattern).getImmediateMatchingExpr() = e1
 }
 
 private module CaptureInput implements VariableCapture::InputSig {

swift/ql/test/library-tests/dataflow/capture/closures.swift

@@ -156,5 +156,5 @@ func sideEffects() {
   var x = 0
   var f = { () in x = source("sideEffects", 1) }
   f()
-  sink(x) // $ MISSING: hasValueFlow=sideEffects
+  sink(x) // $ hasValueFlow=sideEffects
 }

swift/ql/test/library-tests/dataflow/dataflow/LocalFlow.expected

@@ -131,12 +131,14 @@
 | test.swift:147:9:147:9 | SSA def(lambdaSource) | test.swift:151:15:151:15 | lambdaSource |
 | test.swift:147:9:147:9 | lambdaSource | test.swift:147:9:147:9 | SSA def(lambdaSource) |
 | test.swift:147:24:150:5 | { ... } | test.swift:147:9:147:9 | lambdaSource |
+| test.swift:151:15:151:15 | [post] lambdaSource | test.swift:159:16:159:16 | lambdaSource |
 | test.swift:151:15:151:15 | lambdaSource | test.swift:159:16:159:16 | lambdaSource |
 | test.swift:153:9:153:9 | SSA def(lambdaSink) | test.swift:157:5:157:5 | lambdaSink |
 | test.swift:153:9:153:9 | lambdaSink | test.swift:153:9:153:9 | SSA def(lambdaSink) |
 | test.swift:153:22:156:5 | { ... } | test.swift:153:9:153:9 | lambdaSink |
 | test.swift:154:10:154:13 | SSA def(i) | test.swift:155:19:155:19 | i |
 | test.swift:154:10:154:13 | i | test.swift:154:10:154:13 | SSA def(i) |
+| test.swift:157:5:157:5 | [post] lambdaSink | test.swift:159:5:159:5 | lambdaSink |
 | test.swift:157:5:157:5 | lambdaSink | test.swift:159:5:159:5 | lambdaSink |
 | test.swift:162:7:162:7 | SSA def(self) | test.swift:162:7:162:7 | self[return] |
 | test.swift:162:7:162:7 | self | test.swift:162:7:162:7 | SSA def(self) |