Merge pull request #7749 from michaelnebel/csharp/lambda-improvements

C# 10 - Lambda improvements.

csharp/downgrades/4b9c288ece4218779b6113b17af42795f4bbbee1/upgrade.properties

@@ -0,0 +1,3 @@
+description: Remove 'lambda_expr_return_type' relation.
+compatibility: backwards
+lambda_expr_return_type.rel: delete

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

@@ -22,12 +22,13 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
             Parameter.Create(Context, symbol, this);
         }
 
-        private Lambda(ExpressionNodeInfo info, CSharpSyntaxNode body, IEnumerable<ParameterSyntax> @params)
+        private Lambda(ExpressionNodeInfo info, CSharpSyntaxNode body, IEnumerable<ParameterSyntax> @params, TypeSyntax? @return)
             : base(info)
         {
             if (Context.GetModel(info.Node).GetSymbolInfo(info.Node).Symbol is IMethodSymbol symbol)
             {
                 Modifier.ExtractModifiers(Context, info.Context.TrapWriter.Writer, this, symbol);
+                Attribute.ExtractAttributes(Context, symbol, this);
             }
             else
             {
@@ -40,6 +41,13 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
                 foreach (var param in @params)
                     VisitParameter(param);
 
+                if (@return is not null)
+                {
+                    var symbol = Context.GetType(@return);
+                    var type = Entities.Type.Create(Context, symbol);
+                    var trapFile = Context.TrapWriter.Writer;
+                    trapFile.lambda_expr_return_type(this, type.TypeRef);
+                }
                 if (body is ExpressionSyntax exprBody)
                     Create(Context, exprBody, this, 0);
                 else if (body is BlockSyntax blockBody)
@@ -50,17 +58,17 @@ namespace Semmle.Extraction.CSharp.Entities.Expressions
         }
 
         private Lambda(ExpressionNodeInfo info, ParenthesizedLambdaExpressionSyntax node)
-            : this(info.SetKind(ExprKind.LAMBDA), node.Body, node.ParameterList.Parameters) { }
+            : this(info.SetKind(ExprKind.LAMBDA), node.Body, node.ParameterList.Parameters, node.ReturnType) { }
 
         public static Lambda Create(ExpressionNodeInfo info, ParenthesizedLambdaExpressionSyntax node) => new Lambda(info, node);
 
         private Lambda(ExpressionNodeInfo info, SimpleLambdaExpressionSyntax node)
-            : this(info.SetKind(ExprKind.LAMBDA), node.Body, Enumerators.Singleton(node.Parameter)) { }
+            : this(info.SetKind(ExprKind.LAMBDA), node.Body, Enumerators.Singleton(node.Parameter), null) { }
 
         public static Lambda Create(ExpressionNodeInfo info, SimpleLambdaExpressionSyntax node) => new Lambda(info, node);
 
         private Lambda(ExpressionNodeInfo info, AnonymousMethodExpressionSyntax node) :
-            this(info.SetKind(ExprKind.ANONYMOUS_METHOD), node.Body, node.ParameterList is null ? Enumerable.Empty<ParameterSyntax>() : node.ParameterList.Parameters)
+            this(info.SetKind(ExprKind.ANONYMOUS_METHOD), node.Body, node.ParameterList is null ? Enumerable.Empty<ParameterSyntax>() : node.ParameterList.Parameters, null)
         { }
 
         public static Lambda Create(ExpressionNodeInfo info, AnonymousMethodExpressionSyntax node) => new Lambda(info, node);

csharp/extractor/Semmle.Extraction.CSharp/Tuples.cs

@@ -215,6 +215,9 @@ namespace Semmle.Extraction.CSharp
         internal static void indexers(this TextWriter trapFile, Indexer propKey, string name, Type declaringType, Type memberType, Indexer unboundProperty) =>
             trapFile.WriteTuple("indexers", propKey, name, declaringType, memberType, unboundProperty);
 
+        internal static void lambda_expr_return_type(this TextWriter trapFile, Lambda expr, Type returnType) =>
+            trapFile.WriteTuple("lambda_expr_return_type", expr, returnType);
+
         internal static void local_function_stmts(this TextWriter trapFile, Entities.Statements.LocalFunction fnStmt, LocalFunction fn) =>
             trapFile.WriteTuple("local_function_stmts", fnStmt, fn);
 

csharp/ql/lib/change-notes/2022-02-07-lambda-improvements.md

@@ -0,0 +1,6 @@
+---
+category: majorAnalysis
+---
+Added support for C# 10 lambda improvements
+* Explicit return types on lambda expressions.
+* Lambda expression can be tagged with method and return value attributes.

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

@@ -10,8 +10,8 @@ private import TypeRef
  * An element that can have attributes. Either an assembly (`Assembly`), a field (`Field`),
  * a parameter (`Parameter`), an operator (`Operator`), a method (`Method`), a constructor (`Constructor`),
  * a destructor (`Destructor`), a callable accessor (`CallableAccessor`), a value or reference type
- * (`ValueOrRefType`), a declaration with accessors (`DeclarationWithAccessors`), or a local function
- * (`LocalFunction`).
+ * (`ValueOrRefType`), a declaration with accessors (`DeclarationWithAccessors`), a local function
+ * (`LocalFunction`) or a lambda expression (`LambdaExp`).
  */
 class Attributable extends @attributable {
   /** Gets an attribute attached to this element, if any. */

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

@@ -5,6 +5,7 @@
 import Expr
 import semmle.code.csharp.Callable
 private import semmle.code.csharp.frameworks.system.linq.Expressions
+private import semmle.code.csharp.TypeRef
 
 /**
  * Either an object initializer (`ObjectInitializer`) or a collection
@@ -434,6 +435,12 @@ class AnonymousFunctionExpr extends Expr, Callable, Modifiable, @anonymous_funct
  * A lambda expression, for example `(int x) => x + 1`.
  */
 class LambdaExpr extends AnonymousFunctionExpr, @lambda_expr {
+  /* Holds if this lambda expression has explicit return type. */
+  predicate hasExplicitReturnType() { lambda_expr_return_type(this, _) }
+
+  /* Gets the explicit return type of this lambda expression, if any. */
+  Type getExplicitReturnType() { lambda_expr_return_type(this, getTypeRef(result)) }
+
   override string toString() { result = "(...) => ..." }
 
   override string getAPrimaryQlClass() { result = "LambdaExpr" }

csharp/ql/lib/semmlecode.csharp.dbscheme

@@ -191,7 +191,7 @@ sourceLocationPrefix(
 
 @attributable = @assembly | @field | @parameter | @operator | @method | @constructor
               | @destructor | @callable_accessor | @value_or_ref_type | @declaration_with_accessors
-              | @local_function;
+              | @local_function | @lambda_expr;
 
 /** LOCATIONS, ASEMMBLIES, MODULES, FILES and FOLDERS **/
 
@@ -1269,6 +1269,10 @@ expr_argument_name(
   unique int id: @expr ref,
   string name: string ref);
 
+lambda_expr_return_type(
+  unique int id: @lambda_expr ref,
+  int type_id: @type_or_ref ref);
+  
 /** CONTROL/DATA FLOW **/
 
 @control_flow_element = @stmt | @expr;

csharp/ql/lib/upgrades/ab09ac8287516082b7a7367f8fda1862b1be47c5/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add relation 'lambda_expr_return_type' for lambdas with explicit return types.
+compatibility: backwards

csharp/ql/test/library-tests/csharp10/Lambda.cs

@@ -0,0 +1,20 @@
+using System;
+
+public class Lambda
+{
+    public void M1()
+    {
+        // Examples need for implicitly typed lambdas.
+        Func<int, string> f1 = (int x) => x.ToString();
+        var f2 = (int x) => x.ToString();
+
+        // Examples need for  explicit return type for implicitly and explicitly typed lambda.
+        var f3 = object (bool b) => b ? "1" : 0;
+        Func<bool, object> f4 = object (bool b) => b ? "1" : 0;
+
+        // Examples needed for explicit return type for downcast.
+        var f5 = int (bool b) => b ? 1 : 0;
+        var f6 = object (bool b) => b ? 1 : 0;
+    }
+}
+

csharp/ql/test/library-tests/csharp10/LambdaAttributes.cs

@@ -0,0 +1,18 @@
+using System;
+
+public class Example : Attribute
+{
+    public Example(int x) { }
+}
+
+public class LambdaAttributes
+{
+
+    public void M1()
+    {
+        // Examples needed for attributes.
+        var f7 = ([Example(1)] int x) => x.ToString(); // Parameter attribute
+        var f8 =[Example(2)] (int x) => x.ToString(); // Lambda attribute
+        var f9 =[return: Example(3)] (int x) => x.ToString(); // Return value attribute
+    }
+}

csharp/ql/test/library-tests/csharp10/lambda.expected

@@ -0,0 +1,23 @@
+lambdaDeclaration
+| Func<bool, int> | Lambda.cs:16:13:16:14 | f5 | Lambda.cs:16:18:16:42 | (...) => ... |
+| Func<bool, object> | Lambda.cs:12:13:12:14 | f3 | Lambda.cs:12:18:12:47 | (...) => ... |
+| Func<bool, object> | Lambda.cs:13:28:13:29 | f4 | Lambda.cs:13:33:13:62 | (...) => ... |
+| Func<bool, object> | Lambda.cs:17:13:17:14 | f6 | Lambda.cs:17:18:17:45 | (...) => ... |
+| Func<int, string> | Lambda.cs:8:27:8:28 | f1 | Lambda.cs:8:32:8:54 | (...) => ... |
+| Func<int, string> | Lambda.cs:9:13:9:14 | f2 | Lambda.cs:9:18:9:40 | (...) => ... |
+| Func<int, string> | LambdaAttributes.cs:14:13:14:14 | f7 | LambdaAttributes.cs:14:18:14:53 | (...) => ... |
+| Func<int, string> | LambdaAttributes.cs:15:13:15:14 | f8 | LambdaAttributes.cs:15:17:15:52 | (...) => ... |
+| Func<int, string> | LambdaAttributes.cs:16:13:16:14 | f9 | LambdaAttributes.cs:16:17:16:60 | (...) => ... |
+lambdaDeclarationNatural
+| Func<bool, int> | Lambda.cs:16:13:16:14 | f5 | Lambda.cs:16:18:16:42 | (...) => ... |
+| Func<bool, object> | Lambda.cs:12:13:12:14 | f3 | Lambda.cs:12:18:12:47 | (...) => ... |
+| Func<bool, object> | Lambda.cs:17:13:17:14 | f6 | Lambda.cs:17:18:17:45 | (...) => ... |
+| Func<int, string> | Lambda.cs:9:13:9:14 | f2 | Lambda.cs:9:18:9:40 | (...) => ... |
+| Func<int, string> | LambdaAttributes.cs:14:13:14:14 | f7 | LambdaAttributes.cs:14:18:14:53 | (...) => ... |
+| Func<int, string> | LambdaAttributes.cs:15:13:15:14 | f8 | LambdaAttributes.cs:15:17:15:52 | (...) => ... |
+| Func<int, string> | LambdaAttributes.cs:16:13:16:14 | f9 | LambdaAttributes.cs:16:17:16:60 | (...) => ... |
+lambdaDeclarationExplicitReturnType
+| Func<bool, int> | int | int | Lambda.cs:16:13:16:14 | f5 | Lambda.cs:16:18:16:42 | (...) => ... |
+| Func<bool, object> | object | object | Lambda.cs:12:13:12:14 | f3 | Lambda.cs:12:18:12:47 | (...) => ... |
+| Func<bool, object> | object | object | Lambda.cs:13:28:13:29 | f4 | Lambda.cs:13:33:13:62 | (...) => ... |
+| Func<bool, object> | object | object | Lambda.cs:17:13:17:14 | f6 | Lambda.cs:17:18:17:45 | (...) => ... |

csharp/ql/test/library-tests/csharp10/lambda.ql

@@ -0,0 +1,25 @@
+import csharp
+
+private predicate getLambda(
+  LocalVariableDeclAndInitExpr e, string type, LocalVariable v, LambdaExpr lexp
+) {
+  lexp = e.getRValue() and
+  v = e.getTargetVariable() and
+  type = e.getType().toStringWithTypes()
+}
+
+query predicate lambdaDeclaration(string type, LocalVariable v, LambdaExpr lexp) {
+  getLambda(_, type, v, lexp)
+}
+
+query predicate lambdaDeclarationNatural(string type, LocalVariable v, LambdaExpr lexp) {
+  exists(LocalVariableDeclAndInitExpr e | getLambda(e, type, v, lexp) and e.isImplicitlyTyped())
+}
+
+query predicate lambdaDeclarationExplicitReturnType(
+  string type, string explicit, string actual, LocalVariable v, LambdaExpr lexp
+) {
+  getLambda(_, type, v, lexp) and
+  explicit = lexp.getExplicitReturnType().toStringWithTypes() and
+  actual = lexp.getReturnType().toStringWithTypes()
+}

csharp/ql/test/library-tests/csharp10/lambdaAttributes.expected

@@ -0,0 +1,7 @@
+allAttributes
+| LambdaAttributes.cs:14:20:14:26 | [Example(...)] | LambdaAttributes.cs:14:28:14:28 | 1 | Parameter |
+| LambdaAttributes.cs:15:18:15:24 | [Example(...)] | LambdaAttributes.cs:15:26:15:26 | 2 | LambdaExpr |
+| LambdaAttributes.cs:16:26:16:32 | [return: Example(...)] | LambdaAttributes.cs:16:34:16:34 | 3 | LambdaExpr |
+lambdaAttributes
+| LambdaAttributes.cs:15:18:15:24 | [Example(...)] | LambdaAttributes.cs:15:26:15:26 | 2 | LambdaAttributes.cs:15:17:15:52 | (...) => ... |
+| LambdaAttributes.cs:16:26:16:32 | [return: Example(...)] | LambdaAttributes.cs:16:34:16:34 | 3 | LambdaAttributes.cs:16:17:16:60 | (...) => ... |

csharp/ql/test/library-tests/csharp10/lambdaAttributes.ql

@@ -0,0 +1,11 @@
+import csharp
+
+query predicate allAttributes(Attribute a, Expr arg, string c) {
+  a.fromSource() and
+  arg = a.getArgument(0) and
+  c = a.getTarget().(Element).getAPrimaryQlClass()
+}
+
+query predicate lambdaAttributes(Attribute a, Expr arg, LambdaExpr l) {
+  allAttributes(a, arg, _) and a.getTarget() = l
+}