From b0165db87248c5fc2bbbcf41dbe78d0ceba36985 Mon Sep 17 00:00:00 2001
From: Pavel Shevaev <pacha.shevaev@gmail.com>
Date: Fri, 22 Nov 2024 12:12:29 +0300
Subject: [PATCH] Improving blocks parsing in case of errors

---
 src/compile/antlr_proc.cs | 22 ++++++++++++++++------
 tests/test_vm.cs          | 25 +++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/src/compile/antlr_proc.cs b/src/compile/antlr_proc.cs
index 42ee252b..1426dac7 100644
--- a/src/compile/antlr_proc.cs
+++ b/src/compile/antlr_proc.cs
@@ -4914,7 +4914,7 @@ public override object VisitStmParal(bhlParser.StmParalContext ctx)
     LSP_AddSemanticToken(ctx.PARAL(), SemanticToken.Keyword);
 
     var block = ProcBlock(BlockType.PARAL, ctx.block()?.statement());
-    if(block.children.Count == 0)
+    if(block == null)
       AddError(ctx, "empty paral blocks are not allowed");
     return null;
   }
@@ -4924,7 +4924,7 @@ public override object VisitStmParalAll(bhlParser.StmParalAllContext ctx)
     LSP_AddSemanticToken(ctx.PARAL_ALL(), SemanticToken.Keyword);
 
     var block = ProcBlock(BlockType.PARAL_ALL, ctx.block()?.statement());
-    if(block.children.Count == 0)
+    if(block == null)
       AddError(ctx, "empty paral blocks are not allowed");
     return null;
   }
@@ -5123,11 +5123,16 @@ public override object VisitStmWhile(bhlParser.StmWhileContext ctx)
 
     PopBlock(ast);
 
-    return_found.Remove(PeekFuncDecl());
+    BlockResetsCurrentFunctionReturnInfo();
 
     return null;
   }
 
+  void BlockResetsCurrentFunctionReturnInfo()
+  {
+    return_found.Remove(PeekFuncDecl());
+  }
+
   public override object VisitStmDoWhile(bhlParser.StmDoWhileContext ctx)
   {
     LSP_AddSemanticToken(ctx.DO(), SemanticToken.Keyword);
@@ -5158,7 +5163,7 @@ public override object VisitStmDoWhile(bhlParser.StmDoWhileContext ctx)
 
     PopBlock(ast);
 
-    return_found.Remove(PeekFuncDecl());
+    BlockResetsCurrentFunctionReturnInfo();
 
     return null;
   }
@@ -5222,7 +5227,7 @@ public override object VisitStmFor(bhlParser.StmForContext ctx)
     local_scope.Exit();
     PopScope();
 
-    return_found.Remove(PeekFuncDecl());
+    BlockResetsCurrentFunctionReturnInfo();
 
     return null;
   }
@@ -5653,10 +5658,15 @@ AST_Block ProcBlock(BlockType type, IParseTree[] sts)
     PopScope();
 
     if(is_paral)
-      return_found.Remove(PeekFuncDecl());
+      BlockResetsCurrentFunctionReturnInfo();
 
     PopBlock(ast);
 
+    //NOTE: if there are no children, something is definitely wrong
+    //      probably due to parsing errors
+    if(ast.children.Count == 0)
+      return null;
+
     PeekAST().AddChild(ast);
     return ast;
   }
diff --git a/tests/test_vm.cs b/tests/test_vm.cs
index a77b0194..270d56c2 100644
--- a/tests/test_vm.cs
+++ b/tests/test_vm.cs
@@ -4185,6 +4185,31 @@ func int test()
     AssertEqual(3, Execute(vm, "test").result.PopRelease().num);
     CommonChecks(vm);
   }
+  
+  [Fact]
+  public void TestParseErrorInDoWhileBlockWithReturn()
+  {
+    string bhl = @"
+
+    func int test() 
+    {
+      string i;
+      do {
+        return i
+      } while(true)
+    }
+    ";
+    AssertError<Exception>(
+      delegate() { 
+        Compile(bhl);
+      },
+      "incompatible types: 'int' and 'string'",
+      new PlaceAssert(bhl, @"
+        return i
+---------------^"
+      )
+    );
+  }
 
   [Fact]
   public void TestBreakInDoWhile()