GDScript: Fix mishandling of stack pointers

- Replace the for loop temporaries by locals. They cause conflicts with
  the stack when being popped, while locals are properly handled in the
  scope.
- Change the interface for the codegen so the for loop list doesn't live
  through the whole block if it's a temporary.
- Keep track of the actual amount of local variables in the stack. Using
  the size of the map is misleading in cases where multiple locals have
  the same name (which is allowed when there's no shadowing).
- Added a few debug checks for temporaries, to avoid them being wrongly
  manipulated in the future. They should not live more than a line of
  code.
- Rearrange some of compiler code to make sure the temporaries don't
  live across blocks.

1 files changed, 24 insertions, 12 deletions

diff --git a/modules/gdscript/gdscript_compiler.cpp b/modules/gdscript/gdscript_compiler.cpp
index 69fe6d27cc..d47c9accc9 100644
--- a/modules/gdscript/gdscript_compiler.cpp
+++ b/modules/gdscript/gdscript_compiler.cpp
@@ -1474,13 +1474,27 @@ Error GDScriptCompiler::_parse_block(CodeGen &codegen, const GDScriptParser::Sui
 				codegen.start_block();
 
 				// Evaluate the match expression.
+				GDScriptCodeGenerator::Address value_local = codegen.add_local("@match_value", _gdtype_from_datatype(match->test->get_datatype()));
 				GDScriptCodeGenerator::Address value = _parse_expression(codegen, error, match->test);
 				if (error) {
 					return error;
 				}
 
+				// Assign to local.
+				// TODO: This can be improved by passing the target to parse_expression().
+				gen->write_assign(value_local, value);
+
+				if (value.mode == GDScriptCodeGenerator::Address::TEMPORARY) {
+					codegen.generator->pop_temporary();
+				}
+
 				// Then, let's save the type of the value in the stack too, so we can reuse for later comparisons.
-				GDScriptCodeGenerator::Address type = codegen.add_temporary();
+				GDScriptDataType typeof_type;
+				typeof_type.has_type = true;
+				typeof_type.kind = GDScriptDataType::BUILTIN;
+				typeof_type.builtin_type = Variant::INT;
+				GDScriptCodeGenerator::Address type = codegen.add_local("@match_type", typeof_type);
+
 				Vector<GDScriptCodeGenerator::Address> typeof_args;
 				typeof_args.push_back(value);
 				gen->write_call_builtin(type, GDScriptFunctions::TYPE_OF, typeof_args);
@@ -1534,12 +1548,6 @@ Error GDScriptCompiler::_parse_block(CodeGen &codegen, const GDScriptParser::Sui
 					gen->write_endif();
 				}
 
-				gen->pop_temporary();
-
-				if (value.mode == GDScriptCodeGenerator::Address::TEMPORARY) {
-					codegen.generator->pop_temporary();
-				}
-
 				gen->end_match();
 			} break;
 			case GDScriptParser::Node::IF: {
@@ -1577,12 +1585,20 @@ Error GDScriptCompiler::_parse_block(CodeGen &codegen, const GDScriptParser::Sui
 				codegen.start_block();
 				GDScriptCodeGenerator::Address iterator = codegen.add_local(for_n->variable->name, _gdtype_from_datatype(for_n->variable->get_datatype()));
 
+				gen->start_for(iterator.type, _gdtype_from_datatype(for_n->list->get_datatype()));
+
 				GDScriptCodeGenerator::Address list = _parse_expression(codegen, error, for_n->list);
 				if (error) {
 					return error;
 				}
 
-				gen->write_for(iterator, list);
+				gen->write_for_assignment(iterator, list);
+
+				if (list.mode == GDScriptCodeGenerator::Address::TEMPORARY) {
+					codegen.generator->pop_temporary();
+				}
+
+				gen->write_for();
 
 				error = _parse_block(codegen, for_n->loop);
 				if (error) {
@@ -1591,10 +1607,6 @@ Error GDScriptCompiler::_parse_block(CodeGen &codegen, const GDScriptParser::Sui
 
 				gen->write_endfor();
 
-				if (list.mode == GDScriptCodeGenerator::Address::TEMPORARY) {
-					codegen.generator->pop_temporary();
-				}
-
 				codegen.end_block();
 			} break;
 			case GDScriptParser::Node::WHILE: {