Swift: Control-flow through interpolated strings.

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

@@ -96,21 +96,31 @@ module Stmts {
 
     override predicate propagatesAbnormal(ControlFlowElement node) { none() }
 
+    private predicate isBodyOfTapExpr() { any(TapExpr tap).getBody() = ast }
+
+    // Note: If the brace statement is the body of a `TapExpr`, the first element is the variable
+    // declaration (see https://github.com/apple/swift/blob/main/include/swift/AST/Expr.h#L848)
+    // that's initialized by the `Tapxpr`. In `TapExprTre` we've already visited this declaration,
+    // along with its initializer. So we skip the first element here.
+    private AstNode getFirstElement() {
+      if this.isBodyOfTapExpr() then result = ast.getElement(1) else result = ast.getFirstElement()
+    }
+
     override predicate first(ControlFlowElement first) {
       this.firstInner(first)
       or
-      not exists(ast.getFirstElement()) and first.asAstNode() = ast
+      not exists(this.getFirstElement()) and first.asAstNode() = ast
     }
 
     override predicate last(ControlFlowElement last, Completion c) {
       this.lastInner(last, c)
       or
-      not exists(ast.getFirstElement()) and
+      not exists(this.getFirstElement()) and
       last.asAstNode() = ast and
       c instanceof SimpleCompletion
     }
 
-    predicate firstInner(ControlFlowElement first) { astFirst(ast.getFirstElement(), first) }
+    predicate firstInner(ControlFlowElement first) { astFirst(this.getFirstElement(), first) }
 
     /** Gets the body of the i'th `defer` statement. */
     private BraceStmt getDeferStmtBody(int i) {
@@ -1334,10 +1344,34 @@ module Exprs {
     override InterpolatedStringLiteralExpr ast;
 
     final override ControlFlowElement getChildElement(int i) {
-      none() // TODO
+      i = 0 and
+      result.asAstNode() = ast.getAppendingExpr().getFullyConverted()
     }
   }
 
+  private class TapExprTree extends AstStandardPostOrderTree {
+    override TapExpr ast;
+
+    final override ControlFlowElement getChildElement(int i) {
+      i = 0 and
+      result.asAstNode() = ast.getVar()
+      or
+      i = 1 and
+      result.asAstNode() = ast.getSubExpr().getFullyConverted()
+      or
+      // Note: The CFG for the body will skip the first element in the
+      // body because it's guarenteed to be the variable declaration
+      // that we've already visited at i = 0. See the explanation
+      // in `BraceStmtTree` for why this is necessary.
+      i = 2 and
+      result.asAstNode() = ast.getBody()
+    }
+  }
+
+  private class OpaqueValueExprTree extends AstLeafTree {
+    override OpaqueValueExpr ast;
+  }
+
   module DeclRefExprs {
     class DeclRefExprLValueTree extends AstLeafTree {
       override DeclRefExpr ast;

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

@@ -324,7 +324,6 @@ cfg.swift:
 #-----|  -> error
 
 #   40| print(_:separator:terminator:)
-#-----|  -> "..."
 
 #   40| call to print(_:separator:terminator:)
 #-----|  -> 0
@@ -341,12 +340,64 @@ cfg.swift:
 #   40| (Any) ...
 #-----|  -> [...]
 
+#   40| OpaqueValueExpr
+
+#   40| TapExpr
+#-----|  -> "..."
+
+#   40| Unknown error 
+#-----|  -> call to ...
+
 #   40| [...]
 #-----|  -> default separator
 
 #   40| [...]
 #-----|  -> [...]
 
+#   40| call to ...
+#-----|  -> appendInterpolation(_:)
+
+#   40| $interpolation
+#-----|  -> &...
+
+#   40| &...
+#-----|  -> call to appendLiteral(_:)
+
+#   40| call to appendLiteral(_:)
+#-----|  -> Unknown error 
+
+#   40| $interpolation
+#-----|  -> &...
+
+#   40| &...
+#-----|  -> call to appendInterpolation(_:)
+
+#   40| appendInterpolation(_:)
+#-----|  -> $interpolation
+
+#   40| call to appendInterpolation(_:)
+#-----|  -> error
+
+#   40| call to ...
+
+#   40| error
+#-----|  -> call to ...
+
+#   40| 
+#-----|  -> call to ...
+
+#   40| $interpolation
+#-----|  -> &...
+
+#   40| &...
+#-----|  -> call to appendLiteral(_:)
+
+#   40| call to ...
+#-----|  -> TapExpr
+
+#   40| call to appendLiteral(_:)
+#-----|  -> 
+
 #   42| return ...
 #-----| return -> exit tryCatch(x:) (normal)
 
@@ -2817,14 +2868,179 @@ cfg.swift:
 #-----|  -> y
 
 #  262| y
-#-----|  -> "..."
 
 #  263| return ...
 #-----| return -> exit interpolatedString(x:y:) (normal)
 
+#  263| 
+#-----|  -> call to ...
+
 #  263| "..."
 #-----|  -> return ...
 
+#  263| OpaqueValueExpr
+
+#  263| TapExpr
+#-----|  -> "..."
+
+#  263| call to ...
+#-----|  -> appendInterpolation(_:)
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendLiteral(_:)
+
+#  263| call to appendLiteral(_:)
+#-----|  -> 
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendInterpolation(_:)
+
+#  263| appendInterpolation(_:)
+#-----|  -> $interpolation
+
+#  263| call to appendInterpolation(_:)
+#-----|  -> x
+
+#  263| call to ...
+
+#  263| x
+#-----|  -> call to ...
+
+#  263|  + 
+#-----|  -> call to ...
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendLiteral(_:)
+
+#  263| call to ...
+#-----|  -> appendInterpolation(_:)
+
+#  263| call to appendLiteral(_:)
+#-----|  ->  + 
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendInterpolation(_:)
+
+#  263| appendInterpolation(_:)
+#-----|  -> $interpolation
+
+#  263| call to appendInterpolation(_:)
+#-----|  -> y
+
+#  263| call to ...
+
+#  263| y
+#-----|  -> call to ...
+
+#  263|  is equal to 
+#-----|  -> call to ...
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendLiteral(_:)
+
+#  263| call to ...
+#-----|  -> appendInterpolation(_:)
+
+#  263| call to appendLiteral(_:)
+#-----|  ->  is equal to 
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendInterpolation(_:)
+
+#  263| appendInterpolation(_:)
+#-----|  -> $interpolation
+
+#  263| call to appendInterpolation(_:)
+#-----|  -> +(_:_:)
+
+#  263| call to ...
+
+#  263| x
+#-----|  -> y
+
+#  263| ... call to +(_:_:) ...
+#-----|  -> call to ...
+
+#  263| +(_:_:)
+#-----|  -> Int.Type
+
+#  263| Int.Type
+#-----|  -> call to +(_:_:)
+
+#  263| call to +(_:_:)
+#-----|  -> x
+
+#  263| y
+#-----|  -> ... call to +(_:_:) ...
+
+#  263|  and here is a zero: 
+#-----|  -> call to ...
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendLiteral(_:)
+
+#  263| call to ...
+#-----|  -> appendInterpolation(_:)
+
+#  263| call to appendLiteral(_:)
+#-----|  ->  and here is a zero: 
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendInterpolation(_:)
+
+#  263| appendInterpolation(_:)
+#-----|  -> $interpolation
+
+#  263| call to appendInterpolation(_:)
+#-----|  -> returnZero()
+
+#  263| call to ...
+
+#  263| returnZero()
+#-----|  -> call to returnZero()
+
+#  263| call to returnZero()
+#-----|  -> call to ...
+
+#  263| 
+#-----|  -> call to ...
+
+#  263| $interpolation
+#-----|  -> &...
+
+#  263| &...
+#-----|  -> call to appendLiteral(_:)
+
+#  263| call to ...
+#-----|  -> TapExpr
+
+#  263| call to appendLiteral(_:)
+#-----|  -> 
+
 #  266| enter testSubscriptExpr()
 #-----|  -> testSubscriptExpr()