#54 - implement missing return statement check

Author: Stepami

src/Application/HydraScript.Application.StaticAnalysis/Visitors/ReturnAnalyzer.cs

@@ -0,0 +1,45 @@
+using HydraScript.Domain.FrontEnd.Parser;
+using HydraScript.Domain.FrontEnd.Parser.Impl.Ast.Nodes.Declarations.AfterTypesAreLoaded;
+using HydraScript.Domain.FrontEnd.Parser.Impl.Ast.Nodes.Statements;
+
+namespace HydraScript.Application.StaticAnalysis.Visitors;
+
+internal class ReturnAnalyzer : VisitorBase<IAbstractSyntaxTreeNode, ReturnAnalyzerResult>,
+    IVisitor<FunctionDeclaration, ReturnAnalyzerResult>,
+    IVisitor<IfStatement, ReturnAnalyzerResult>,
+    IVisitor<ReturnStatement, ReturnAnalyzerResult>
+{
+    public ReturnAnalyzerResult Visit(FunctionDeclaration visitable)
+    {
+        IAbstractSyntaxTreeNode astNode = visitable;
+        return Visit(astNode);
+    }
+
+    public override ReturnAnalyzerResult Visit(IAbstractSyntaxTreeNode visitable)
+    {
+        var result = ReturnAnalyzerResult.AdditiveIdentity;
+        for (var i = 0; i < visitable.Count; i++)
+        {
+            var visitableResult = visitable[i].Accept(This);
+            if (visitableResult.CodePathEndedWithReturn)
+                return visitableResult * result;
+            result += visitableResult;
+        }
+
+        return result;
+    }
+
+    public ReturnAnalyzerResult Visit(IfStatement visitable)
+    {
+        var thenReturns = visitable.Then.Accept(This);
+
+        if (visitable.Else is null)
+            return thenReturns + ReturnAnalyzerResult.AdditiveIdentity;
+        var elseReturns = visitable.Else.Accept(This);
+
+        return thenReturns + elseReturns;
+    }
+
+    public ReturnAnalyzerResult Visit(ReturnStatement visitable) =>
+        new(CodePathEndedWithReturn: true, ReturnStatements: [visitable]);
+}

src/Application/HydraScript.Application.StaticAnalysis/Visitors/ReturnAnalyzerResult.cs

@@ -0,0 +1,22 @@
+using System.Numerics;
+using HydraScript.Domain.FrontEnd.Parser.Impl.Ast.Nodes.Statements;
+
+namespace HydraScript.Application.StaticAnalysis.Visitors;
+
+public sealed record ReturnAnalyzerResult(bool CodePathEndedWithReturn, IReadOnlyList<ReturnStatement> ReturnStatements) :
+    IAdditiveIdentity<ReturnAnalyzerResult, ReturnAnalyzerResult>,
+    IAdditionOperators<ReturnAnalyzerResult, ReturnAnalyzerResult, ReturnAnalyzerResult>,
+    IMultiplyOperators<ReturnAnalyzerResult, ReturnAnalyzerResult, ReturnAnalyzerResult>
+{
+    public static ReturnAnalyzerResult operator +(ReturnAnalyzerResult left, ReturnAnalyzerResult right) =>
+        new(
+            left.CodePathEndedWithReturn && right.CodePathEndedWithReturn,
+            ReturnStatements: [..left.ReturnStatements, ..right.ReturnStatements]);
+
+    public static ReturnAnalyzerResult AdditiveIdentity { get; } = new(CodePathEndedWithReturn: false, ReturnStatements: []);
+
+    public static ReturnAnalyzerResult operator *(ReturnAnalyzerResult left, ReturnAnalyzerResult right) =>
+        new(
+            left.CodePathEndedWithReturn || right.CodePathEndedWithReturn,
+            ReturnStatements: [..left.ReturnStatements, ..right.ReturnStatements]);
+}