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

C# 10 - Lambda improvements.

Author: michaelnebel

csharp/downgrades/4b9c288ece4218779b6113b17af42795f4bbbee1/old.dbscheme

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

csharp/downgrades/4b9c288ece4218779b6113b17af42795f4bbbee1/semmlecode.csharp.dbscheme

@@ -22,12 +22,13 @@ private void VisitParameter(ParameterSyntax p)
             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 @@ private Lambda(ExpressionNodeInfo info, CSharpSyntaxNode body, IEnumerable<Param
                 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 @@ private Lambda(ExpressionNodeInfo info, CSharpSyntaxNode body, IEnumerable<Param
         }
 
         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/downgrades/4b9c288ece4218779b6113b17af42795f4bbbee1/upgrade.properties

@@ -215,6 +215,9 @@ internal static void indexer_location(this TextWriter trapFile, Indexer indexer,
         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/extractor/Semmle.Extraction.CSharp/Entities/Expressions/Lambda.cs

@@ -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/extractor/Semmle.Extraction.CSharp/Tuples.cs

@@ -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/change-notes/2022-02-07-lambda-improvements.md

@@ -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/semmle/code/csharp/Attribute.qll

@@ -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;