Merge pull request github#4662 from tamasvajk/feature/csharp9-type-pattern

C#: Extract type patterns

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Patterns/Pattern.cs

@@ -17,6 +17,9 @@ internal static Expression Create(Context cx, PatternSyntax syntax, IExpressionP
                 case ConstantPatternSyntax constantPattern:
                     return Expression.Create(cx, constantPattern.Expression, parent, child);
 
+                case TypePatternSyntax typePattern:
+                    return Expressions.TypeAccess.Create(cx, typePattern.Type, parent, child);
+
                 case DeclarationPatternSyntax declPattern:
                     // Creates a single local variable declaration.
                     {

csharp/ql/test/library-tests/csharp9/PrintAst.expected

@@ -348,3 +348,52 @@ TypeParameterNullability.cs:
 #   24|         -1: [TypeMention] T?
 #   24|           1: [TypeMention] T
 #   24|     4: [BlockStmt] {...}
+TypePattern.cs:
+#    3| [Class] TypePattern
+#    5|   5: [Method] M1
+#    5|     -1: [TypeMention] object
+#-----|     2: (Parameters)
+#    5|       0: [Parameter] o1
+#    5|         -1: [TypeMention] object
+#    5|       1: [Parameter] o2
+#    5|         -1: [TypeMention] object
+#    6|     4: [BlockStmt] {...}
+#    7|       0: [LocalVariableDeclStmt] ... ...;
+#    7|         0: [LocalVariableDeclAndInitExpr] (Object,Object) t = ...
+#    7|           -1: [TypeMention] (object, object)
+#    7|           0: [LocalVariableAccess] access to local variable t
+#    7|           1: [TupleExpr] (..., ...)
+#    7|             0: [ParameterAccess] access to parameter o1
+#    7|             1: [ParameterAccess] access to parameter o2
+#    8|       1: [IfStmt] if (...) ...
+#    8|         0: [IsExpr] ... is ...
+#    8|           0: [LocalVariableAccess] access to local variable t
+#    8|           1: [RecursivePatternExpr] { ... }
+#    8|             2: [PositionalPatternExpr] ( ... )
+#    8|               0: [TypeAccessPatternExpr] access to type Int32
+#    8|                 0: [TypeMention] int
+#    8|               1: [TypeAccessPatternExpr] access to type String
+#    8|                 0: [TypeMention] string
+#    8|         1: [BlockStmt] {...}
+#    9|       2: [ReturnStmt] return ...;
+#    9|         0: [SwitchExpr] ... switch { ... }
+#    9|           -1: [ParameterAccess] access to parameter o1
+#   11|           0: [SwitchCaseExpr] ... => ...
+#   11|             0: [TypeAccessPatternExpr] access to type Int32
+#   11|               0: [TypeMention] int
+#   11|             2: [CastExpr] (...) ...
+#   11|               1: [IntLiteral] 1
+#   12|           1: [SwitchCaseExpr] ... => ...
+#   12|             0: [VariablePatternExpr] Double d
+#   12|               0: [TypeMention] double
+#   12|             2: [CastExpr] (...) ...
+#   12|               1: [LocalVariableAccess] access to local variable d
+#   13|           2: [SwitchCaseExpr] ... => ...
+#   13|             0: [TypeAccessPatternExpr] access to type String
+#   13|               0: [TypeMention] string
+#   13|             2: [CastExpr] (...) ...
+#   13|               1: [IntLiteral] 3
+#   14|           3: [SwitchCaseExpr] ... => ...
+#   14|             0: [VariablePatternExpr] Object o
+#   14|               0: [TypeMention] object
+#   14|             2: [LocalVariableAccess] access to local variable o

csharp/ql/test/library-tests/csharp9/TypePattern.cs

@@ -0,0 +1,17 @@
+using System;
+
+public class TypePattern
+{
+    object M1(object o1, object o2)
+    {
+        var t = (o1, o2);
+        if (t is (int, string)) {}
+        return o1 switch
+        {
+            int => 1,
+            double d => d,
+            System.String => 3,
+            System.Object o => o
+        };
+    }
+}

csharp/ql/test/library-tests/csharp9/typePattern.expected

@@ -0,0 +1,9 @@
+| ParenthesizedPattern.cs:25:13:25:15 | T t | T |
+| ParenthesizedPattern.cs:26:14:26:22 | Object o1 | Object |
+| ParenthesizedPattern.cs:27:14:27:19 | access to type String | String |
+| TypePattern.cs:8:19:8:21 | access to type Int32 | Int32 |
+| TypePattern.cs:8:24:8:29 | access to type String | String |
+| TypePattern.cs:11:13:11:15 | access to type Int32 | Int32 |
+| TypePattern.cs:12:13:12:20 | Double d | Double |
+| TypePattern.cs:13:13:13:25 | access to type String | String |
+| TypePattern.cs:14:13:14:27 | Object o | Object |

csharp/ql/test/library-tests/csharp9/typePattern.ql

@@ -0,0 +1,4 @@
+import csharp
+
+from TypePatternExpr pattern
+select pattern, pattern.getCheckedType().toString()