C#: Fix switch case expression types

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Switch.cs

@@ -18,18 +18,19 @@ private Switch(ExpressionNodeInfo info) : base(info.SetKind(ExprKind.SWITCH))
         protected override void PopulateExpression(TextWriter trapFile)
         {
             SwitchedExpr = Expression.Create(cx, Syntax.GoverningExpression, this, -1);
-            int child = 0;
-            foreach (var arm in Syntax.Arms)
+            for (var i = 0; i < Syntax.Arms.Count; i++)
             {
-                new SwitchCase(cx, arm, this, child++);
+                new SwitchCase(cx, Syntax.Arms[i], this, i);
             }
         }
     }
 
     class SwitchCase : Expression
     {
         internal SwitchCase(Context cx, SwitchExpressionArmSyntax arm, Switch parent, int child) :
-            base(new ExpressionInfo(cx, parent.SwitchedExpr.Type, cx.Create(arm.GetLocation()), ExprKind.SWITCH_CASE, parent, child, false, null))
+            base(new ExpressionInfo(
+                cx, Entities.Type.Create(cx, cx.GetType(arm.Expression)), cx.Create(arm.GetLocation()),
+                ExprKind.SWITCH_CASE, parent, child, false, null))
         {
             cx.CreatePattern(arm.Pattern, this, 0);
             if (arm.WhenClause is WhenClauseSyntax when)

csharp/ql/test/library-tests/controlflow/guards/Implications.expected

@@ -397,8 +397,14 @@
 | Guards.cs:276:16:276:16 | access to parameter o | match access to type Action<Object> | Guards.cs:276:16:276:16 | access to parameter o | non-null |
 | Guards.cs:276:16:276:16 | access to parameter o | match null | Guards.cs:276:16:276:16 | access to parameter o | null |
 | Guards.cs:276:16:276:16 | access to parameter o | non-match null | Guards.cs:276:16:276:16 | access to parameter o | non-null |
+| Guards.cs:278:13:279:28 | ... => ... | true | Guards.cs:276:16:276:16 | access to parameter o | non-null |
+| Guards.cs:280:13:281:28 | ... => ... | true | Guards.cs:276:16:276:16 | access to parameter o | non-null |
 | Guards.cs:281:17:281:17 | access to local variable a | non-null | Guards.cs:276:16:276:16 | access to parameter o | non-null |
 | Guards.cs:281:17:281:17 | access to local variable a | null | Guards.cs:276:16:276:16 | access to parameter o | null |
+| Guards.cs:282:13:283:28 | ... => ... | true | Guards.cs:276:16:276:16 | access to parameter o | non-null |
+| Guards.cs:284:13:285:28 | ... => ... | false | Guards.cs:276:16:276:16 | access to parameter o | non-null |
+| Guards.cs:284:13:285:28 | ... => ... | true | Guards.cs:276:16:276:16 | access to parameter o | null |
+| Guards.cs:286:13:287:28 | ... => ... | true | Guards.cs:276:16:276:16 | access to parameter o | non-null |
 | Guards.cs:296:16:296:17 | access to local variable b2 | match true | Guards.cs:294:13:294:14 | access to parameter b1 | false |
 | Guards.cs:296:16:296:17 | access to local variable b2 | match true | Guards.cs:296:16:296:17 | access to local variable b2 | true |
 | Guards.cs:308:16:308:17 | access to local variable b2 | match true | Guards.cs:306:13:306:14 | access to parameter b1 | true |

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

@@ -1,16 +1,16 @@
-| patterns.cs:101:34:101:40 | "large" | Int32 |
-| patterns.cs:102:18:102:24 | "small" | Int32 |
+| patterns.cs:101:34:101:40 | "large" | String |
+| patterns.cs:102:18:102:24 | "small" | String |
 | patterns.cs:110:22:110:26 | (..., ...) | (Int32,Int32) |
 | patterns.cs:111:22:111:26 | (..., ...) | (Int32,Int32) |
 | patterns.cs:117:27:117:33 | (..., ...) | (Int32,Int32) |
 | patterns.cs:118:28:118:34 | (..., ...) | (Int32,Int32) |
 | patterns.cs:119:33:119:38 | (..., ...) | (Int32,Int32) |
-| patterns.cs:128:49:128:49 | 0 | MyStruct |
-| patterns.cs:129:38:129:38 | 1 | MyStruct |
-| patterns.cs:130:23:130:23 | 2 | MyStruct |
-| patterns.cs:131:27:131:27 | 3 | MyStruct |
-| patterns.cs:138:22:138:50 | throw ... | Object |
-| patterns.cs:139:22:139:22 | 3 | Object |
-| patterns.cs:140:42:140:42 | 4 | Object |
-| patterns.cs:141:29:141:29 | 5 | Object |
-| patterns.cs:142:41:142:41 | 6 | Object |
+| patterns.cs:128:49:128:49 | 0 | Int32 |
+| patterns.cs:129:38:129:38 | 1 | Int32 |
+| patterns.cs:130:23:130:23 | 2 | Int32 |
+| patterns.cs:131:27:131:27 | 3 | Int32 |
+| patterns.cs:138:22:138:50 | throw ... | null |
+| patterns.cs:139:22:139:22 | 3 | Int32 |
+| patterns.cs:140:42:140:42 | 4 | Int32 |
+| patterns.cs:141:29:141:29 | 5 | Int32 |
+| patterns.cs:142:41:142:41 | 6 | Int32 |