Merge pull request github#4612 from tamasvajk/feature/csharp9-local-function-without-body

C#: C#9 Extract local functions without body

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CSharp/Entities/LocalFunction.cs

@@ -34,17 +34,7 @@ private class LocalFunctionFactory : ICachedEntityFactory<IMethodSymbol, LocalFu
         public override void Populate(TextWriter trapFile)
         {
             PopulateMethod(trapFile);
-
-            // There is a "bug" in Roslyn whereby the IMethodSymbol associated with the local function symbol
-            // is always static, so we need to go to the syntax reference of the local function to see whether
-            // the "static" modifier is present.
-            if (symbol.DeclaringSyntaxReferences.SingleOrDefault().GetSyntax() is LocalFunctionStatementSyntax fn)
-            {
-                foreach (var modifier in fn.Modifiers)
-                {
-                    Modifier.HasModifier(Context, trapFile, this, modifier.Text);
-                }
-            }
+            PopulateModifiers(trapFile);
 
             var originalDefinition = IsSourceDeclaration ? this : Create(Context, symbol.OriginalDefinition);
             var returnType = Type.Create(Context, symbol.ReturnType);

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/LocalFunction.cs

@@ -26,13 +26,8 @@ private IMethodSymbol Symbol
         {
             get
             {
-                // Ideally model.GetDeclaredSymbol(Stmt) would do
-                // the right thing but it doesn't exist.
-                // So instead, we have to do the lookup via GetEnclosingSymbol.
-
                 var m = cx.GetModel(Stmt);
-                var body = Stmt.Body == null ? Stmt.ExpressionBody : (CSharpSyntaxNode)Stmt.Body;
-                return m.GetEnclosingSymbol(body.GetLocation().SourceSpan.Start) as IMethodSymbol;
+                return m.GetDeclaredSymbol(Stmt) as IMethodSymbol;
             }
         }
 

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

@@ -1 +1,3 @@
+| StaticLocalFunctions.cs:9:9:9:33 | I | private |
 | StaticLocalFunctions.cs:9:9:9:33 | I | static |
+| StaticLocalFunctions.cs:10:9:10:28 | J | private |

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

@@ -0,0 +1,18 @@
+using System;
+using System.Threading.Tasks;
+
+public class Class1
+{
+    public async Task M1()
+    {
+        int? i = 1;
+        async Task<int?> mul(int mul)
+        {
+            return mul * i;
+        }
+
+        await mul(2);
+
+        static extern void localExtern();
+    }
+}

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

@@ -0,0 +1,8 @@
+noBody
+| LocalFunction.cs:16:9:16:41 | localExtern |
+localFunctionModifier
+| LocalFunction.cs:9:9:12:9 | mul | async |
+| LocalFunction.cs:9:9:12:9 | mul | private |
+| LocalFunction.cs:16:9:16:41 | localExtern | extern |
+| LocalFunction.cs:16:9:16:41 | localExtern | private |
+| LocalFunction.cs:16:9:16:41 | localExtern | static |

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

@@ -0,0 +1,8 @@
+noBody
+| LocalFunction.cs:16:9:16:41 | localExtern |
+localFunctionModifier
+| LocalFunction.cs:9:9:12:9 | mul | async |
+| LocalFunction.cs:9:9:12:9 | mul | private |
+| LocalFunction.cs:16:9:16:41 | localExtern | extern |
+| LocalFunction.cs:16:9:16:41 | localExtern | private |
+| LocalFunction.cs:16:9:16:41 | localExtern | static |

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

@@ -0,0 +1,7 @@
+import csharp
+
+query predicate noBody(LocalFunction lf) { not lf.hasBody() }
+
+query predicate localFunctionModifier(LocalFunction lf, string modifier) {
+  lf.hasModifier(modifier)
+}

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

@@ -47,6 +47,36 @@ Discard.cs:
 #   10|             4: [BlockStmt] {...}
 #   10|               0: [ReturnStmt] return ...;
 #   10|                 0: [IntLiteral] 0
+LocalFunction.cs:
+#    4| [Class] Class1
+#    6|   5: [Method] M1
+#    6|     -1: [TypeMention] Task
+#    7|     4: [BlockStmt] {...}
+#    8|       0: [LocalVariableDeclStmt] ... ...;
+#    8|         0: [LocalVariableDeclAndInitExpr] Nullable<Int32> i = ...
+#    8|           -1: [TypeMention] int?
+#    8|             1: [TypeMention] int
+#    8|           0: [LocalVariableAccess] access to local variable i
+#    8|           1: [CastExpr] (...) ...
+#    8|             1: [IntLiteral] 1
+#    9|       1: [LocalFunctionStmt] mul(...)
+#    9|         0: [LocalFunction] mul
+#-----|           2: (Parameters)
+#    9|             0: [Parameter] mul
+#    9|               -1: [TypeMention] int
+#   10|           4: [BlockStmt] {...}
+#   11|             0: [ReturnStmt] return ...;
+#   11|               0: [MulExpr] ... * ...
+#   11|                 0: [CastExpr] (...) ...
+#   11|                   1: [ParameterAccess] access to parameter mul
+#   11|                 1: [LocalVariableAccess] access to local variable i
+#   14|       2: [ExprStmt] ...;
+#   14|         0: [AwaitExpr] await ...
+#   14|           0: [LocalFunctionCall] call to local function mul
+#   14|             -1: [LocalFunctionAccess] access to local function mul
+#   14|             0: [IntLiteral] 2
+#   16|       3: [LocalFunctionStmt] localExtern(...)
+#   16|         0: [LocalFunction] localExtern
 NativeInt.cs:
 #    3| [Class] NativeInt
 #    5|   5: [Method] M1