Swift: Control flow through #available.

Author: geoffw0

swift/ql/lib/codeql/swift/controlflow/internal/Completion.qll

@@ -122,6 +122,8 @@ private predicate inBooleanContext(ControlFlowElement n) {
 private predicate astInBooleanContext(AstNode n) {
   n = any(ConditionElement condElem).getBoolean().getFullyUnresolved()
   or
+  n = any(ConditionElement condElem).getAvailability().getFullyUnresolved()
+  or
   n = any(StmtCondition stmtCond).getFullyUnresolved()
   or
   exists(RepeatWhileStmt repeat | n = repeat.getCondition().getFullyConverted())

swift/ql/lib/codeql/swift/controlflow/internal/ControlFlowGraphImpl.qll

@@ -249,15 +249,23 @@ module Stmts {
       child.asAstNode() = ast.getAnElement().getPattern().getFullyUnresolved()
       or
       child.asAstNode() = ast.getAnElement().getBoolean().getFullyConverted()
+      or
+      child.asAstNode() = ast.getAnElement().getAvailability().getFullyUnresolved()
     }
 
     predicate firstElement(int i, ControlFlowElement first) {
       // If there is an initializer in the first element, evaluate that first
       astFirst(ast.getElement(i).getInitializer().getFullyConverted(), first)
       or
-      // Otherwise, the first element is a boolean condition.
+      // Otherwise, the first element is...
       not exists(ast.getElement(i).getInitializer()) and
-      astFirst(ast.getElement(i).getBoolean().getFullyConverted(), first)
+      (
+        // ... a boolean condition.
+        astFirst(ast.getElement(i).getBoolean().getFullyConverted(), first)
+        or
+        // ... or an availability check ...
+        astFirst(ast.getElement(i).getAvailability().getFullyUnresolved(), first)
+      )
     }
 
     predicate succElement(int i, ControlFlowElement pred, ControlFlowElement succ, Completion c) {
@@ -272,6 +280,9 @@ module Stmts {
         or
         // ... or the boolean ...
         astLast(ast.getElement(i).getBoolean().getFullyConverted(), pred, c)
+        or
+        // ... or the availability check ...
+        astLast(ast.getElement(i).getAvailability().getFullyUnresolved(), pred, c)
       ) and
       // We evaluate the next element
       c instanceof NormalCompletion and
@@ -287,11 +298,17 @@ module Stmts {
       astLast(ast.getAnElement().getPattern().getFullyUnresolved(), last, c) and
       not c.(MatchingCompletion).isMatch()
       or
+      // Stop if an availability check failed
+      astLast(ast.getAnElement().getAvailability().getFullyUnresolved(), last, c) and
+      c instanceof FalseCompletion
+      or
       // Stop if we successfully evaluated all the conditionals
       (
         astLast(ast.getLastElement().getBoolean().getFullyConverted(), last, c)
         or
         astLast(ast.getLastElement().getPattern().getFullyUnresolved(), last, c)
+        or
+        astLast(ast.getLastElement().getAvailability().getFullyUnresolved(), last, c)
       ) and
       c instanceof NormalCompletion
     }
@@ -1770,6 +1787,20 @@ module Exprs {
   }
 }
 
+module AvailabilityInfo {
+  private class AvailabilityInfoTree extends AstStandardPostOrderTree {
+    override AvailabilityInfo ast;
+
+    final override ControlFlowElement getChildElement(int i) {
+      result.asAstNode() = ast.getSpec(i).getFullyUnresolved()
+    }
+  }
+
+  private class AvailabilitySpecTree extends AstLeafTree {
+    override AvailabilitySpec ast;
+  }
+}
+
 private Scope parent(Scope n) {
   result = n.getOuterScope() and
   not n instanceof CfgScope::Range_

swift/ql/test/library-tests/controlflow/graph/Cfg.expected

@@ -6329,6 +6329,11 @@ cfg.swift:
 #  496| enter testAvailable()
 #-----|  -> testAvailable()
 
+#  496| exit testAvailable()
+
+#  496| exit testAvailable() (normal)
+#-----|  -> exit testAvailable()
+
 #  496| testAvailable()
 #-----|  -> x
 
@@ -6347,4 +6352,191 @@ cfg.swift:
 #  499| if ... then { ... }
 #-----|  -> StmtCondition
 
+#  499| #available
+#-----| true -> .+=(_:_:)
+#-----| false -> if ... then { ... }
+
 #  499| StmtCondition
+#-----|  -> macOS 10
+
+#  499| macOS 10
+#-----|  -> *
+
+#  499| *
+#-----|  -> #available
+
+#  500| &...
+#-----|  -> 1
+
+#  500| x
+#-----|  -> &...
+
+#  500| ... .+=(_:_:) ...
+#-----|  -> if ... then { ... }
+
+#  500| .+=(_:_:)
+#-----|  -> Int.Type
+
+#  500| Int.Type
+#-----|  -> x
+
+#  500| 1
+#-----|  -> ... .+=(_:_:) ...
+
+#  503| if ... then { ... }
+#-----|  -> StmtCondition
+
+#  503| #available
+#-----| true -> .+=(_:_:)
+#-----| false -> if ... then { ... }
+
+#  503| StmtCondition
+#-----|  -> macOS 10.13
+
+#  503| macOS 10.13
+#-----|  -> *
+
+#  503| *
+#-----|  -> #available
+
+#  504| &...
+#-----|  -> 1
+
+#  504| x
+#-----|  -> &...
+
+#  504| ... .+=(_:_:) ...
+#-----|  -> if ... then { ... }
+
+#  504| .+=(_:_:)
+#-----|  -> Int.Type
+
+#  504| Int.Type
+#-----|  -> x
+
+#  504| 1
+#-----|  -> ... .+=(_:_:) ...
+
+#  507| if ... then { ... }
+#-----|  -> StmtCondition
+
+#  507| #unavailable
+#-----| true -> .+=(_:_:)
+#-----| false -> guard ... else { ... }
+
+#  507| StmtCondition
+#-----|  -> iOS 10
+
+#  507| iOS 10
+#-----|  -> watchOS 10
+
+#  507| watchOS 10
+#-----|  -> macOS 10
+
+#  507| macOS 10
+#-----|  -> #unavailable
+
+#  508| &...
+#-----|  -> 1
+
+#  508| x
+#-----|  -> &...
+
+#  508| ... .+=(_:_:) ...
+#-----|  -> guard ... else { ... }
+
+#  508| .+=(_:_:)
+#-----|  -> Int.Type
+
+#  508| Int.Type
+#-----|  -> x
+
+#  508| 1
+#-----|  -> ... .+=(_:_:) ...
+
+#  511| guard ... else { ... }
+#-----|  -> StmtCondition
+
+#  511| #available
+#-----| false -> .+=(_:_:)
+#-----| true -> if ... then { ... }
+
+#  511| StmtCondition
+#-----|  -> macOS 12
+
+#  511| macOS 12
+#-----|  -> *
+
+#  511| *
+#-----|  -> #available
+
+#  512| &...
+#-----|  -> 1
+
+#  512| x
+#-----|  -> &...
+
+#  512| ... .+=(_:_:) ...
+#-----|  -> if ... then { ... }
+
+#  512| .+=(_:_:)
+#-----|  -> Int.Type
+
+#  512| Int.Type
+#-----|  -> x
+
+#  512| 1
+#-----|  -> ... .+=(_:_:) ...
+
+#  515| if ... then { ... }
+#-----|  -> StmtCondition
+
+#  515| #available
+#-----| false, true -> iOS 12
+#-----| false -> x
+
+#  515| StmtCondition
+#-----|  -> macOS 12
+
+#  515| macOS 12
+#-----|  -> *
+
+#  515| *
+#-----|  -> #available
+
+#  515| #available
+#-----| true -> .+=(_:_:)
+#-----| false -> x
+
+#  515| iOS 12
+#-----|  -> *
+
+#  515| *
+#-----|  -> #available
+
+#  516| &...
+#-----|  -> 1
+
+#  516| x
+#-----|  -> &...
+
+#  516| ... .+=(_:_:) ...
+#-----|  -> x
+
+#  516| .+=(_:_:)
+#-----|  -> Int.Type
+
+#  516| Int.Type
+#-----|  -> x
+
+#  516| 1
+#-----|  -> ... .+=(_:_:) ...
+
+#  519| return ...
+#-----| return -> exit testAvailable() (normal)
+
+#  519| (Int) ...
+#-----|  -> return ...
+
+#  519| x
+#-----|  -> (Int) ...