C#: Introduce a TuplePatternExpr class.

csharp/ql/lib/semmle/code/csharp/Assignable.qll

@@ -277,15 +277,28 @@ module AssignableInternal {
     def = TParameterDefaultDefinition(_, result)
   }
 
-  /** A local variable declaration at the top-level of a pattern. */
-  class TopLevelPatternDecl extends LocalVariableDeclExpr {
+  /** A pattern containing a local variable declaration. */
+  class LocalVariablePatternDecl extends LocalVariableDeclExpr {
     private PatternMatch pm;
 
-    TopLevelPatternDecl() { this = pm.getPattern().(BindingPatternExpr).getVariableDeclExpr() }
+    LocalVariablePatternDecl() {
+      exists(BindingPatternExpr bpe |
+        this = bpe.getVariableDeclExpr() and pm = bpe.getPatternMatch()
+      )
+    }
+
+    /** Holds if the local variable definition is at the top level of the pattern. */
+    predicate isTopLevel() { this = pm.getPattern().(BindingPatternExpr).getVariableDeclExpr() }
 
+    /** Gets the pattern match that this local variable declaration (pattern) belongs to. */
     PatternMatch getMatch() { result = pm }
   }
 
+  /** A local variable declaration at the top-level of a pattern. */
+  class TopLevelPatternDecl extends LocalVariablePatternDecl {
+    TopLevelPatternDecl() { this.isTopLevel() }
+  }
+
   cached
   private module Cached {
     cached
@@ -305,7 +318,7 @@ module AssignableInternal {
       TLocalVariableDefinition(LocalVariableDeclExpr lvde) {
         not lvde.hasInitializer() and
         not exists(getTupleSource(TTupleAssignmentDefinition(_, lvde))) and
-        not lvde instanceof TopLevelPatternDecl and
+        not lvde instanceof LocalVariablePatternDecl and
         not lvde.isOutArgument()
       } or
       TImplicitParameterDefinition(Parameter p) {
@@ -324,7 +337,7 @@ module AssignableInternal {
         default = p.getDefaultValue()
       } or
       TAddressOfDefinition(AddressOfExpr aoe) or
-      TPatternDefinition(TopLevelPatternDecl tlpd) or
+      TPatternDefinition(LocalVariablePatternDecl lvpd) or
       TAssignOperationDefinition(AssignOperation ao) {
         ao instanceof AssignCallExpr and not ao instanceof CompoundAssignmentOperatorCall
         or
@@ -737,24 +750,31 @@ module AssignableDefinitions {
   }
 
   /**
-   * A local variable definition in a pattern, for example `x is int i`.
+   * A local variable definition in a pattern, for example `int i` in `x is int i`.
    */
   class PatternDefinition extends AssignableDefinition, TPatternDefinition {
-    TopLevelPatternDecl tlpd;
+    LocalVariablePatternDecl lvpd;
 
-    PatternDefinition() { this = TPatternDefinition(tlpd) }
+    PatternDefinition() { this = TPatternDefinition(lvpd) }
 
     /** Gets the element matches against this pattern. */
-    PatternMatch getMatch() { result = tlpd.getMatch() }
+    PatternMatch getMatch() { result = lvpd.getMatch() }
 
     /** Gets the underlying local variable declaration. */
-    LocalVariableDeclExpr getDeclaration() { result = tlpd }
-
-    override Expr getSource() { result = this.getMatch().getExpr() }
+    LocalVariableDeclExpr getDeclaration() { result = lvpd }
 
     override string toString() { result = this.getDeclaration().toString() }
   }
 
+  /**
+   * A local variable definition at the top level of a pattern.
+   */
+  class TopLevelPatternDefinition extends PatternDefinition {
+    TopLevelPatternDefinition() { lvpd.isTopLevel() }
+
+    override Expr getSource() { result = this.getMatch().getExpr() }
+  }
+
   /**
    * An initializer definition for a field or a property, for example
    * line 2 in

csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll

@@ -110,7 +110,7 @@ private predicate nonNullDef(SsaExplicitWrite def) {
   def.getValue() instanceof NonNullExpr
   or
   exists(AssignableDefinition ad | ad = def.getDefinition() |
-    ad instanceof AssignableDefinitions::PatternDefinition
+    ad instanceof AssignableDefinitions::TopLevelPatternDefinition
     or
     ad =
       any(AssignableDefinitions::LocalVariableDefinition d |

csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll

@@ -560,7 +560,7 @@ module LocalFlow {
     or
     exists(AssignExpr ae | ae.getLeftOperand().(TupleExpr) = e2 and ae.getRightOperand() = e1)
     or
-    exists(ControlFlowElement cfe | cfe = e2.(TupleExpr).(PatternExpr).getPatternMatch() |
+    exists(ControlFlowElement cfe | cfe = e2.(TuplePatternExpr).getPatternMatch() |
       cfe.(IsExpr).getExpr() = e1
       or
       exists(Switch sw | sw.getACase() = cfe and sw.getExpr() = e1)
@@ -2242,8 +2242,8 @@ private predicate readContentStep(Node node1, Content c, Node node2) {
     )
     or
     // item = variable in node1 = (..., variable, ...) in a case/is var (..., ...)
-    isPatternExprDescendant(te) and
-    exists(AssignableDefinitions::LocalVariableDefinition lvd |
+    te instanceof TuplePatternExpr and
+    exists(AssignableDefinitions::PatternDefinition lvd |
       node2.(AssignableDefinitionNode).getDefinition() = lvd and
       lvd.getDeclaration() = item
     )
@@ -2677,7 +2677,7 @@ class CastNode extends Node {
     this.asExpr() instanceof Cast
     or
     this.(AssignableDefinitionNode).getDefinition() instanceof
-      AssignableDefinitions::PatternDefinition
+      AssignableDefinitions::TopLevelPatternDefinition
   }
 }
 

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

@@ -547,6 +547,13 @@ class PositionalPatternExpr extends PatternExpr, @positional_pattern_expr {
   override string getAPrimaryQlClass() { result = "PositionalPatternExpr" }
 }
 
+/**
+ * A tuple pattern. For example, `var (x, y)`.
+ */
+class TuplePatternExpr extends TupleExpr, PatternExpr {
+  override string getAPrimaryQlClass() { result = "TuplePatternExpr" }
+}
+
 /** A list pattern. For example `[1, 2, int y]` in `x is [1, 2, int y]`. */
 class ListPatternExpr extends PatternExpr, @list_pattern_expr {
   override string toString() { result = "[ ... ]" }

csharp/ql/src/Dead Code/DeadStoreOfLocal.ql

@@ -35,7 +35,7 @@ class RelevantDefinition extends AssignableDefinition {
         not lvde.getName() = "_"
       )
     or
-    this instanceof AssignableDefinitions::PatternDefinition
+    this instanceof AssignableDefinitions::TopLevelPatternDefinition
     or
     this instanceof AssignableDefinitions::AssignOperationDefinition
   }

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

@@ -929,7 +929,7 @@ patterns.cs:
 #   57|               1: [ConstantPatternExpr,IntLiteral] 2
 #   58|         10: [BreakStmt] break;
 #   59|         11: [CaseStmt] case ...:
-#   59|           0: [TupleExpr] (..., ...)
+#   59|           0: [TuplePatternExpr] (..., ...)
 #   59|             0: [VariablePatternExpr] Int32 x
 #   59|             1: [VariablePatternExpr] Int32 y
 #   60|         12: [BreakStmt] break;
@@ -1156,7 +1156,7 @@ patterns.cs:
 #  130|                   1: [ConstantPatternExpr,IntLiteral] 2
 #  130|               2: [IntLiteral] 2
 #  131|             3: [SwitchCaseExpr] ... => ...
-#  131|               0: [TupleExpr] (..., ...)
+#  131|               0: [TuplePatternExpr] (..., ...)
 #  131|                 0: [VariablePatternExpr] Int32 x
 #  131|                 1: [DiscardPatternExpr] _
 #  131|               2: [IntLiteral] 3

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

@@ -262,9 +262,9 @@ Tuples.cs:
 #   65|                   -1: [LocalVariableAccess] access to local variable t
 #   66|         4: [BreakStmt] break;
 #   67|         5: [CaseStmt] case ...:
-#   67|           0: [TupleExpr] (..., ...)
+#   67|           0: [TuplePatternExpr] (..., ...)
 #   67|             0: [VariablePatternExpr] String a
-#   67|             1: [TupleExpr] (..., ...)
+#   67|             1: [TuplePatternExpr] (..., ...)
 #   67|               0: [VariablePatternExpr] Int32 b
 #   67|               1: [VariablePatternExpr] String c
 #   67|             2: [DiscardPatternExpr] _
@@ -302,7 +302,7 @@ Tuples.cs:
 #   78|           0: [RecursivePatternExpr] { ... }
 #   78|             2: [PositionalPatternExpr] ( ... )
 #   78|               0: [VariablePatternExpr] String a
-#   78|               1: [TupleExpr] (..., ...)
+#   78|               1: [TuplePatternExpr] (..., ...)
 #   78|                 0: [VariablePatternExpr] Int32 b
 #   78|                 1: [VariablePatternExpr] String c
 #   78|               2: [DiscardPatternExpr] _
@@ -335,9 +335,9 @@ Tuples.cs:
 #   87|       7: [IfStmt] if (...) ...
 #   87|         0: [IsExpr] ... is ...
 #   87|           0: [LocalVariableAccess] access to local variable x
-#   87|           1: [TupleExpr] (..., ...)
+#   87|           1: [TuplePatternExpr] (..., ...)
 #   87|             0: [VariablePatternExpr] String p
-#   87|             1: [TupleExpr] (..., ...)
+#   87|             1: [TuplePatternExpr] (..., ...)
 #   87|               0: [VariablePatternExpr] Int32 q
 #   87|               1: [VariablePatternExpr] String r
 #   87|             2: [DiscardPatternExpr] _
@@ -417,7 +417,7 @@ Tuples.cs:
 #  107|       6: [SwitchStmt] switch (...) {...}
 #  107|         0: [LocalVariableAccess] access to local variable r
 #  109|         0: [CaseStmt] case ...:
-#  109|           0: [TupleExpr] (..., ...)
+#  109|           0: [TuplePatternExpr] (..., ...)
 #  109|             0: [VariablePatternExpr] String x
 #  109|             1: [VariablePatternExpr] Int32 y
 #  110|         1: [ExprStmt] ...;