C#: Add missing tuple declarations to PatternExpr

`x` and `y` in `pair is var (x, y) ? x : null` are now correctly part of `PatternExpr`.

Author: hvitved

csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll

@@ -316,6 +316,12 @@ private predicate hasChildPattern(ControlFlowElement pm, Expr child) {
     child = mid.getChildExpr(0) or
     child = mid.getChildExpr(1)
   )
+  or
+  exists(Expr mid |
+    hasChildPattern(pm, mid) and
+    mid instanceof @tuple_expr and
+    child = mid.getAChildExpr()
+  )
 }
 
 /**
@@ -420,13 +426,10 @@ class TypeAccessPatternExpr extends TypePatternExpr, TypeAccess {
   override string getAPrimaryQlClass() { result = "TypeAccessPatternExpr" }
 }
 
-/** A pattern that may bind a variable, for example `string s` in `x is string s`. */
-class BindingPatternExpr extends PatternExpr {
-  BindingPatternExpr() {
-    this instanceof LocalVariableDeclExpr or
-    this instanceof @recursive_pattern_expr
-  }
+private class TBindingPatternExpr = @local_var_decl_expr or @recursive_pattern_expr;
 
+/** A pattern that may bind a variable, for example `string s` in `x is string s`. */
+class BindingPatternExpr extends PatternExpr, TBindingPatternExpr {
   /**
    * Gets the local variable declaration of this pattern, if any. For example,
    * `string s` in `string { Length: 5 } s`.

csharp/ql/test/library-tests/csharp8/PrintAst.expected

@@ -932,8 +932,8 @@ patterns.cs:
 #   58|         10: [BreakStmt] break;
 #   59|         11: [CaseStmt] case ...:
 #   59|           0: [TupleExpr] (..., ...)
-#   59|             0: [LocalVariableDeclExpr] Int32 x
-#   59|             1: [LocalVariableDeclExpr] Int32 y
+#   59|             0: [VariablePatternExpr] Int32 x
+#   59|             1: [VariablePatternExpr] Int32 y
 #   60|         12: [BreakStmt] break;
 #   61|         13: [DefaultCase] default:
 #   62|         14: [BreakStmt] break;
@@ -1159,8 +1159,8 @@ patterns.cs:
 #  130|               2: [IntLiteral] 2
 #  131|             3: [SwitchCaseExpr] ... => ...
 #  131|               0: [TupleExpr] (..., ...)
-#  131|                 0: [LocalVariableDeclExpr] Int32 x
-#  131|                 1: [DiscardExpr] _
+#  131|                 0: [VariablePatternExpr] Int32 x
+#  131|                 1: [DiscardPatternExpr] _
 #  131|               2: [IntLiteral] 3
 #  134|       2: [TryStmt] try {...} ...
 #  135|         0: [BlockStmt] {...}

csharp/ql/test/library-tests/dataflow/tuples/DataFlowStep.expected

@@ -57,6 +57,7 @@
 | Tuples.cs:50:17:50:56 | (..., ...) | Tuples.cs:50:13:50:56 | SSA def(x) |
 | Tuples.cs:51:17:51:17 | access to local variable x | Tuples.cs:53:18:53:57 | SSA def(t) |
 | Tuples.cs:51:17:51:17 | access to local variable x | Tuples.cs:58:18:58:35 | (..., ...) |
+| Tuples.cs:51:17:51:17 | access to local variable x | Tuples.cs:58:18:58:35 | (..., ...) |
 | Tuples.cs:51:17:51:17 | access to local variable x | Tuples.cs:77:13:77:13 | access to local variable x |
 | Tuples.cs:53:18:53:57 | SSA def(t) | Tuples.cs:53:64:53:64 | access to local variable t |
 | Tuples.cs:53:18:53:57 | SSA qualifier def(t.Item1) | Tuples.cs:54:22:54:28 | access to field Item1 |
@@ -92,6 +93,7 @@
 | Tuples.cs:70:22:70:28 | [post] access to field Item2 | Tuples.cs:72:22:72:28 | access to field Item2 |
 | Tuples.cs:70:22:70:28 | access to field Item2 | Tuples.cs:72:22:72:28 | access to field Item2 |
 | Tuples.cs:77:13:77:13 | access to local variable x | Tuples.cs:77:18:77:35 | (..., ...) |
+| Tuples.cs:77:13:77:13 | access to local variable x | Tuples.cs:77:18:77:35 | (..., ...) |
 | Tuples.cs:77:23:77:23 | SSA def(p) | Tuples.cs:79:18:79:18 | access to local variable p |
 | Tuples.cs:77:27:77:27 | SSA def(q) | Tuples.cs:81:18:81:18 | access to local variable q |
 | Tuples.cs:77:30:77:30 | SSA def(r) | Tuples.cs:80:18:80:18 | access to local variable r |

csharp/ql/test/library-tests/dataflow/tuples/PrintAst.expected

@@ -206,11 +206,11 @@ Tuples.cs:
 #   57|         4: [BreakStmt] break;
 #   58|         5: [CaseStmt] case ...:
 #   58|           0: [TupleExpr] (..., ...)
-#   58|             0: [LocalVariableDeclExpr] String a
+#   58|             0: [VariablePatternExpr] String a
 #   58|             1: [TupleExpr] (..., ...)
-#   58|               0: [LocalVariableDeclExpr] Int32 b
-#   58|               1: [LocalVariableDeclExpr] String c
-#   58|             2: [DiscardExpr] _
+#   58|               0: [VariablePatternExpr] Int32 b
+#   58|               1: [VariablePatternExpr] String c
+#   58|             2: [DiscardPatternExpr] _
 #   59|         6: [ExprStmt] ...;
 #   59|           0: [MethodCall] call to method Sink<String>
 #   59|             0: [LocalVariableAccess] access to local variable a
@@ -238,8 +238,8 @@ Tuples.cs:
 #   68|             2: [PositionalPatternExpr] ( ... )
 #   68|               0: [ConstantPatternExpr,StringLiteral] "taint source"
 #   68|               1: [TupleExpr] (..., ...)
-#   68|                 0: [LocalVariableDeclExpr] Int32 b
-#   68|                 1: [LocalVariableDeclExpr] String c
+#   68|                 0: [VariablePatternExpr] Int32 b
+#   68|                 1: [VariablePatternExpr] String c
 #   68|               2: [DiscardPatternExpr] _
 #   69|         1: [ExprStmt] ...;
 #   69|           0: [MethodCall] call to method Sink<String>
@@ -266,11 +266,11 @@ Tuples.cs:
 #   77|         0: [IsExpr] ... is ...
 #   77|           0: [LocalVariableAccess] access to local variable x
 #   77|           1: [TupleExpr] (..., ...)
-#   77|             0: [LocalVariableDeclExpr] String p
+#   77|             0: [VariablePatternExpr] String p
 #   77|             1: [TupleExpr] (..., ...)
-#   77|               0: [LocalVariableDeclExpr] Int32 q
-#   77|               1: [LocalVariableDeclExpr] String r
-#   77|             2: [DiscardExpr] _
+#   77|               0: [VariablePatternExpr] Int32 q
+#   77|               1: [VariablePatternExpr] String r
+#   77|             2: [DiscardPatternExpr] _
 #   78|         1: [BlockStmt] {...}
 #   79|           0: [ExprStmt] ...;
 #   79|             0: [MethodCall] call to method Sink<String>
@@ -339,8 +339,8 @@ Tuples.cs:
 #   96|         0: [LocalVariableAccess] access to local variable r
 #   98|         0: [CaseStmt] case ...:
 #   98|           0: [TupleExpr] (..., ...)
-#   98|             0: [LocalVariableDeclExpr] String x
-#   98|             1: [LocalVariableDeclExpr] Int32 y
+#   98|             0: [VariablePatternExpr] String x
+#   98|             1: [VariablePatternExpr] Int32 y
 #   99|         1: [ExprStmt] ...;
 #   99|           0: [MethodCall] call to method Sink<String>
 #   99|             0: [LocalVariableAccess] access to local variable x