Merge pull request #6845 from karroffel/master

Adds pattern matching to GDScript

modules/gdscript/gd_compiler.cpp

@@ -1099,6 +1099,71 @@ Error GDCompiler::_parse_block(CodeGen& codegen,const GDParser::BlockNode *p_blo
 
 				switch(cf->cf_type) {
 
+					case GDParser::ControlFlowNode::CF_MATCH: {
+						GDParser::MatchNode *match = cf->match;
+						
+						GDParser::IdentifierNode *id = memnew(GDParser::IdentifierNode);
+						id->name = "#match_value";
+						
+						// var #match_value
+						// copied because there is no _parse_statement :(
+						codegen.add_stack_identifier(id->name, p_stack_level++);
+						codegen.alloc_stack(p_stack_level);
+						new_identifiers++;
+
+						GDParser::OperatorNode *op = memnew(GDParser::OperatorNode);
+						op->op=GDParser::OperatorNode::OP_ASSIGN;
+						op->arguments.push_back(id);
+						op->arguments.push_back(match->val_to_match);
+						
+						int ret = _parse_expression(codegen, op, p_stack_level);
+						if (ret < 0) {
+							return ERR_PARSE_ERROR;
+						}
+						
+						// break address
+						codegen.opcodes.push_back(GDFunction::OPCODE_JUMP);
+						codegen.opcodes.push_back(codegen.opcodes.size() + 3);
+						int break_addr = codegen.opcodes.size();
+						codegen.opcodes.push_back(GDFunction::OPCODE_JUMP);
+						codegen.opcodes.push_back(0); // break addr
+						
+						for (int j = 0; j < match->compiled_pattern_branches.size(); j++) {
+							GDParser::MatchNode::CompiledPatternBranch branch = match->compiled_pattern_branches[j];
+							
+							// jump over continue
+							// jump unconditionally
+							// continue address
+							// compile the condition
+							int ret = _parse_expression(codegen, branch.compiled_pattern, p_stack_level);
+							if (ret < 0) {
+								return ERR_PARSE_ERROR;
+							}
+							
+							codegen.opcodes.push_back(GDFunction::OPCODE_JUMP_IF);
+							codegen.opcodes.push_back(ret);
+							codegen.opcodes.push_back(codegen.opcodes.size() + 3);
+							int continue_addr = codegen.opcodes.size();
+							codegen.opcodes.push_back(GDFunction::OPCODE_JUMP);
+							codegen.opcodes.push_back(0);
+							
+							
+							
+							Error err = _parse_block(codegen, branch.body, p_stack_level, p_break_addr, continue_addr);
+							if (err) {
+								return ERR_PARSE_ERROR;
+							}
+							
+							codegen.opcodes.push_back(GDFunction::OPCODE_JUMP);
+							codegen.opcodes.push_back(break_addr);
+							
+							codegen.opcodes[continue_addr + 1] = codegen.opcodes.size();
+						}
+						
+						codegen.opcodes[break_addr + 1] = codegen.opcodes.size();
+						
+						
+					} break;
 					
 					case GDParser::ControlFlowNode::CF_IF: {
 

modules/gdscript/gd_parser.cpp

@@ -1679,6 +1679,542 @@ bool GDParser::_recover_from_completion() {
 	return true;
 }
 
+GDParser::PatternNode *GDParser::_parse_pattern(bool p_static)
+{
+	
+	PatternNode *pattern = alloc_node<PatternNode>();
+	
+	GDTokenizer::Token token = tokenizer->get_token();
+	if (error_set)
+		return NULL;
+	
+	if (token == GDTokenizer::TK_EOF) {
+		return NULL;
+	}
+	
+	switch (token) {
+		// dictionary
+		case GDTokenizer::TK_BRACKET_OPEN: {
+			tokenizer->advance();
+			pattern->pt_type = GDParser::PatternNode::PT_ARRAY;
+			while (true) {
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_BRACKET_CLOSE) {
+					tokenizer->advance();
+					break;
+				}
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_PERIOD && tokenizer->get_token(1) == GDTokenizer::TK_PERIOD) {
+					// match everything
+					tokenizer->advance(2);
+					PatternNode *sub_pattern = alloc_node<PatternNode>();
+					sub_pattern->pt_type = GDParser::PatternNode::PT_IGNORE_REST;
+					pattern->array.push_back(sub_pattern);
+					if (tokenizer->get_token() == GDTokenizer::TK_COMMA && tokenizer->get_token(1) == GDTokenizer::TK_BRACKET_CLOSE) {
+						tokenizer->advance(2);
+						break;
+					} else if (tokenizer->get_token() == GDTokenizer::TK_BRACKET_CLOSE) {
+						tokenizer->advance(1);
+						break;
+					} else {
+						_set_error("'..' pattern only allowed at the end of an array pattern");
+						return NULL;
+					}
+				}
+				
+				PatternNode *sub_pattern = _parse_pattern(p_static);
+				if (!sub_pattern) {
+					return NULL;
+				}
+				
+				pattern->array.push_back(sub_pattern);
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_COMMA) {
+					tokenizer->advance();
+					continue;
+				} else if (tokenizer->get_token() == GDTokenizer::TK_BRACKET_CLOSE) {
+					tokenizer->advance();
+					break;
+				} else {
+					_set_error("Not a valid pattern");
+					return NULL;
+				}
+			}
+		} break;
+		// bind
+		case GDTokenizer::TK_PR_VAR: {
+			tokenizer->advance();
+			pattern->pt_type = GDParser::PatternNode::PT_BIND;
+			pattern->bind = tokenizer->get_token_identifier();
+			tokenizer->advance();
+		} break;
+		// array
+		case GDTokenizer::TK_CURLY_BRACKET_OPEN: {
+			tokenizer->advance();
+			pattern->pt_type = GDParser::PatternNode::PT_DICTIONARY;
+			while (true) {
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_CURLY_BRACKET_CLOSE) {
+					tokenizer->advance();
+					break;
+				}
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_PERIOD && tokenizer->get_token(1) == GDTokenizer::TK_PERIOD) {
+					// match everything
+					tokenizer->advance(2);
+					PatternNode *sub_pattern = alloc_node<PatternNode>();
+					sub_pattern->pt_type = PatternNode::PT_IGNORE_REST;
+					pattern->array.push_back(sub_pattern);
+					if (tokenizer->get_token() == GDTokenizer::TK_COMMA && tokenizer->get_token(1) == GDTokenizer::TK_CURLY_BRACKET_CLOSE) {
+						tokenizer->advance(2);
+						break;
+					} else if (tokenizer->get_token() == GDTokenizer::TK_CURLY_BRACKET_CLOSE) {
+						tokenizer->advance(1);
+						break;
+					} else {
+						_set_error("'..' pattern only allowed at the end of an dictionary pattern");
+						return NULL;
+					}
+				}
+				
+				Node *key = _parse_and_reduce_expression(pattern, p_static);
+				if (!key) {
+					_set_error("Not a valid key in pattern");
+					return NULL;
+				}
+				
+				if (key->type != GDParser::Node::TYPE_CONSTANT) {
+					_set_error("Not a constant expression as key");
+					return NULL;
+				}
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_COLON) {
+					tokenizer->advance();
+					
+					PatternNode *value = _parse_pattern(p_static);
+					if (!value) {
+						_set_error("Expected pattern in dictionary value");
+						return NULL;
+					}
+					
+					pattern->dictionary.insert(static_cast<ConstantNode*>(key), value);
+				} else {
+					pattern->dictionary.insert(static_cast<ConstantNode*>(key), NULL);
+				}
+				
+				
+				if (tokenizer->get_token() == GDTokenizer::TK_COMMA) {
+					tokenizer->advance();
+					continue;
+				} else if (tokenizer->get_token() == GDTokenizer::TK_CURLY_BRACKET_CLOSE) {
+					tokenizer->advance();
+					break;
+				} else {
+					_set_error("Not a valid pattern");
+					return NULL;
+				}
+			}
+		} break;
+		// all the constants like strings and numbers
+		default: {
+			Node *value = _parse_and_reduce_expression(pattern, p_static);
+			if (error_set) {
+				return NULL;
+			}
+			if (value->type == Node::TYPE_IDENTIFIER && static_cast<IdentifierNode*>(value)->name == "_") {
+				// wildcard pattern
+				pattern->pt_type = PatternNode::PT_WILDCARD;
+				break;
+			}
+			
+			if (value->type != Node::TYPE_IDENTIFIER && value->type != Node::TYPE_CONSTANT) {
+				_set_error("Only constant expressions or variables allowed in a pattern");
+				return NULL;
+			}
+			
+			pattern->pt_type = PatternNode::PT_CONSTANT;
+			pattern->constant = value;
+		} break;
+	}
+	
+	return pattern;
+}
+
+void GDParser::_parse_pattern_block(BlockNode *p_block, Vector<PatternBranchNode*> &p_branches, bool p_static)
+{
+	int indent_level = tab_level.back()->get();
+	
+	while (true) {
+		
+		while (tokenizer->get_token() == GDTokenizer::TK_NEWLINE && _parse_newline());
+		
+		// GDTokenizer::Token token = tokenizer->get_token();
+		if (error_set)
+			return;
+		
+		if (indent_level > tab_level.back()->get()) {
+			return; // go back a level
+		}
+		
+		if (pending_newline!=-1) {
+			pending_newline=-1;
+		}
+		
+		PatternBranchNode *branch = alloc_node<PatternBranchNode>();
+		
+		branch->patterns.push_back(_parse_pattern(p_static));
+		if (!branch->patterns[0]) {
+			return;
+		}
+		
+		while (tokenizer->get_token() == GDTokenizer::TK_COMMA) {
+			tokenizer->advance();
+			branch->patterns.push_back(_parse_pattern(p_static));
+			if (!branch->patterns[branch->patterns.size() - 1]) {
+				return;
+			}
+		}
+		
+		if(!_enter_indent_block()) {
+			_set_error("Expected block in pattern branch");
+			return;
+		}
+		
+		branch->body = alloc_node<BlockNode>();
+		branch->body->parent_block = p_block;
+		p_block->sub_blocks.push_back(branch->body);
+		current_block = branch->body;
+		
+		_parse_block(branch->body, p_static);
+		
+		current_block = p_block;
+		
+		p_branches.push_back(branch);
+	}
+}
+
+
+void GDParser::_generate_pattern(PatternNode *p_pattern, Node *p_node_to_match, Node *&p_resulting_node, Map<StringName, Node*> &p_bindings)
+{
+	switch (p_pattern->pt_type) {
+		case PatternNode::PT_CONSTANT: {
+			
+			// typecheck
+			BuiltInFunctionNode *typeof_node = alloc_node<BuiltInFunctionNode>();
+			typeof_node->function = GDFunctions::TYPE_OF;
+			
+			OperatorNode *typeof_match_value = alloc_node<OperatorNode>();
+			typeof_match_value->op = OperatorNode::OP_CALL;
+			typeof_match_value->arguments.push_back(typeof_node);
+			typeof_match_value->arguments.push_back(p_node_to_match);
+			
+			OperatorNode *typeof_pattern_value = alloc_node<OperatorNode>();
+			typeof_pattern_value->op = OperatorNode::OP_CALL;
+			typeof_pattern_value->arguments.push_back(typeof_node);
+			typeof_pattern_value->arguments.push_back(p_pattern->constant);
+			
+			OperatorNode *type_comp = alloc_node<OperatorNode>();
+			type_comp->op = OperatorNode::OP_EQUAL;
+			type_comp->arguments.push_back(typeof_match_value);
+			type_comp->arguments.push_back(typeof_pattern_value);
+			
+			
+			// comare the actual values
+			OperatorNode *value_comp = alloc_node<OperatorNode>();
+			value_comp->op = OperatorNode::OP_EQUAL;
+			value_comp->arguments.push_back(p_pattern->constant);
+			value_comp->arguments.push_back(p_node_to_match);
+			
+			
+			OperatorNode *comparison = alloc_node<OperatorNode>();
+			comparison->op = OperatorNode::OP_AND;
+			comparison->arguments.push_back(type_comp);
+			comparison->arguments.push_back(value_comp);
+			
+			p_resulting_node = comparison;
+			
+		} break;
+		case PatternNode::PT_BIND: {
+			p_bindings[p_pattern->bind] = p_node_to_match;
+			
+			// a bind always matches
+			ConstantNode *true_value = alloc_node<ConstantNode>();
+			true_value->value = Variant(true);
+			p_resulting_node = true_value;
+		} break;
+		case PatternNode::PT_ARRAY: {
+			
+			bool open_ended = false;
+	
+			if (p_pattern->array.size() > 0) {
+				if (p_pattern->array[p_pattern->array.size() - 1]->pt_type == PatternNode::PT_IGNORE_REST) {
+					open_ended = true;
+				}
+			}
+			
+			// typeof(value_to_match) == TYPE_ARRAY && value_to_match.size() >= length
+			// typeof(value_to_match) == TYPE_ARRAY && value_to_match.size() == length
+			
+			{
+				// typecheck
+				BuiltInFunctionNode *typeof_node = alloc_node<BuiltInFunctionNode>();
+				typeof_node->function = GDFunctions::TYPE_OF;
+				
+				OperatorNode *typeof_match_value = alloc_node<OperatorNode>();
+				typeof_match_value->op = OperatorNode::OP_CALL;
+				typeof_match_value->arguments.push_back(typeof_node);
+				typeof_match_value->arguments.push_back(p_node_to_match);
+				
+				IdentifierNode *typeof_array = alloc_node<IdentifierNode>();
+				typeof_array->name = "TYPE_ARRAY";
+				
+				OperatorNode *type_comp = alloc_node<OperatorNode>();
+				type_comp->op = OperatorNode::OP_EQUAL;
+				type_comp->arguments.push_back(typeof_match_value);
+				type_comp->arguments.push_back(typeof_array);
+				
+				
+				// size
+				ConstantNode *length = alloc_node<ConstantNode>();
+				length->value = Variant(open_ended ? p_pattern->array.size() - 1 : p_pattern->array.size());
+				
+				OperatorNode *call = alloc_node<OperatorNode>();
+				call->op = OperatorNode::OP_CALL;
+				call->arguments.push_back(p_node_to_match);
+				
+				IdentifierNode *size = alloc_node<IdentifierNode>();
+				size->name = "size";
+				call->arguments.push_back(size);
+				
+				OperatorNode *length_comparison = alloc_node<OperatorNode>();
+				length_comparison->op = open_ended ? OperatorNode::OP_GREATER_EQUAL : OperatorNode::OP_EQUAL;
+				length_comparison->arguments.push_back(call);
+				length_comparison->arguments.push_back(length);
+				
+				OperatorNode *type_and_length_comparison = alloc_node<OperatorNode>();
+				type_and_length_comparison->op = OperatorNode::OP_AND;
+				type_and_length_comparison->arguments.push_back(type_comp);
+				type_and_length_comparison->arguments.push_back(length_comparison);
+				
+				p_resulting_node = type_and_length_comparison;
+			}
+			
+			
+			
+			for (int i = 0; i < p_pattern->array.size(); i++) {
+				PatternNode *pattern = p_pattern->array[i];
+				
+				Node *condition = NULL;
+				
+				ConstantNode *index = alloc_node<ConstantNode>();
+				index->value = Variant(i);
+				
+				OperatorNode *indexed_value = alloc_node<OperatorNode>();
+				indexed_value->op = OperatorNode::OP_INDEX;
+				indexed_value->arguments.push_back(p_node_to_match);
+				indexed_value->arguments.push_back(index);
+				
+				_generate_pattern(pattern, indexed_value, condition, p_bindings);
+				
+				// concatenate all the patterns with &&
+				OperatorNode *and_node = alloc_node<OperatorNode>();
+				and_node->op = OperatorNode::OP_AND;
+				and_node->arguments.push_back(p_resulting_node);
+				and_node->arguments.push_back(condition);
+				
+				p_resulting_node = and_node;
+			}
+			
+			
+		} break;
+		case PatternNode::PT_DICTIONARY: {
+			
+			bool open_ended = false;
+			
+			if (p_pattern->array.size() > 0) {
+				open_ended = true;
+			}
+			
+			// typeof(value_to_match) == TYPE_DICTIONARY && value_to_match.size() >= length
+			// typeof(value_to_match) == TYPE_DICTIONARY && value_to_match.size() == length
+			
+			
+			{
+				// typecheck
+				BuiltInFunctionNode *typeof_node = alloc_node<BuiltInFunctionNode>();
+				typeof_node->function = GDFunctions::TYPE_OF;
+				
+				OperatorNode *typeof_match_value = alloc_node<OperatorNode>();
+				typeof_match_value->op = OperatorNode::OP_CALL;
+				typeof_match_value->arguments.push_back(typeof_node);
+				typeof_match_value->arguments.push_back(p_node_to_match);
+				
+				IdentifierNode *typeof_dictionary = alloc_node<IdentifierNode>();
+				typeof_dictionary->name = "TYPE_DICTIONARY";
+				
+				OperatorNode *type_comp = alloc_node<OperatorNode>();
+				type_comp->op = OperatorNode::OP_EQUAL;
+				type_comp->arguments.push_back(typeof_match_value);
+				type_comp->arguments.push_back(typeof_dictionary);
+				
+				// size
+				ConstantNode *length = alloc_node<ConstantNode>();
+				length->value = Variant(open_ended ? p_pattern->dictionary.size() - 1 : p_pattern->dictionary.size());
+				
+				OperatorNode *call = alloc_node<OperatorNode>();
+				call->op = OperatorNode::OP_CALL;
+				call->arguments.push_back(p_node_to_match);
+				
+				IdentifierNode *size = alloc_node<IdentifierNode>();
+				size->name = "size";
+				call->arguments.push_back(size);
+				
+				OperatorNode *length_comparison = alloc_node<OperatorNode>();
+				length_comparison->op = open_ended ? OperatorNode::OP_GREATER_EQUAL : OperatorNode::OP_EQUAL;
+				length_comparison->arguments.push_back(call);
+				length_comparison->arguments.push_back(length);
+				
+				OperatorNode *type_and_length_comparison = alloc_node<OperatorNode>();
+				type_and_length_comparison->op = OperatorNode::OP_AND;
+				type_and_length_comparison->arguments.push_back(type_comp);
+				type_and_length_comparison->arguments.push_back(length_comparison);
+				
+				p_resulting_node = type_and_length_comparison;
+			}
+			
+			
+			
+			for (Map<ConstantNode*, PatternNode*>::Element *e = p_pattern->dictionary.front(); e; e = e->next()) {
+				
+				Node *condition = NULL;
+				
+				// chech for has, then for pattern
+				
+				IdentifierNode *has = alloc_node<IdentifierNode>();
+				has->name = "has";
+				
+				OperatorNode *has_call = alloc_node<OperatorNode>();
+				has_call->op = OperatorNode::OP_CALL;
+				has_call->arguments.push_back(p_node_to_match);
+				has_call->arguments.push_back(has);
+				has_call->arguments.push_back(e->key());
+					
+				
+				if (e->value()) {
+					
+					OperatorNode *indexed_value = alloc_node<OperatorNode>();
+					indexed_value->op = OperatorNode::OP_INDEX;
+					indexed_value->arguments.push_back(p_node_to_match);
+					indexed_value->arguments.push_back(e->key());
+					
+					_generate_pattern(e->value(), indexed_value, condition, p_bindings);
+					
+					OperatorNode *has_and_pattern = alloc_node<OperatorNode>();
+					has_and_pattern->op = OperatorNode::OP_AND;
+					has_and_pattern->arguments.push_back(has_call);
+					has_and_pattern->arguments.push_back(condition);
+					
+					condition = has_and_pattern;
+
+				} else {
+					condition = has_call;
+				}
+				
+				
+				
+				// concatenate all the patterns with &&
+				OperatorNode *and_node = alloc_node<OperatorNode>();
+				and_node->op = OperatorNode::OP_AND;
+				and_node->arguments.push_back(p_resulting_node);
+				and_node->arguments.push_back(condition);
+				
+				p_resulting_node = and_node;
+			}
+			
+		} break;
+		case PatternNode::PT_IGNORE_REST:
+		case PatternNode::PT_WILDCARD: {
+			// simply generate a `true`
+			ConstantNode *true_value = alloc_node<ConstantNode>();
+			true_value->value = Variant(true);
+			p_resulting_node = true_value;
+		} break;
+		default: {
+			
+		} break;
+	}
+}
+
+void GDParser::_transform_match_statment(BlockNode *p_block, MatchNode *p_match_statement)
+{
+	IdentifierNode *id = alloc_node<IdentifierNode>();
+	id->name = "#match_value";
+	
+	for (int i = 0; i < p_match_statement->branches.size(); i++) {
+		
+		PatternBranchNode *branch = p_match_statement->branches[i];
+		
+		MatchNode::CompiledPatternBranch compiled_branch;
+		compiled_branch.compiled_pattern = NULL;
+		
+		Map<StringName, Node*> binding;
+		
+		for (int j = 0; j < branch->patterns.size(); j++) {
+			PatternNode *pattern = branch->patterns[j];
+			
+			Map<StringName, Node*> bindings;
+			Node *resulting_node;
+			_generate_pattern(pattern, id, resulting_node, bindings);
+			
+			if (!binding.empty() && !bindings.empty()) {
+				_set_error("Multipatterns can't contain bindings");
+				return;
+			} else {
+				binding = bindings;
+			}
+			
+			if (compiled_branch.compiled_pattern) {
+				OperatorNode *or_node = alloc_node<OperatorNode>();
+				or_node->op = OperatorNode::OP_OR;
+				or_node->arguments.push_back(compiled_branch.compiled_pattern);
+				or_node->arguments.push_back(resulting_node);
+				
+				compiled_branch.compiled_pattern = or_node;
+			} else {
+				// single pattern | first one
+				compiled_branch.compiled_pattern = resulting_node;
+			}
+			
+		}
+		
+		
+		// prepare the body ...hehe
+		for (Map<StringName, Node*>::Element *e = binding.front(); e; e = e->next()) {
+			LocalVarNode *local_var = alloc_node<LocalVarNode>();
+			local_var->name = e->key();
+			local_var->assign = e->value();
+
+			
+			IdentifierNode *id = alloc_node<IdentifierNode>();
+			id->name = local_var->name;
+
+			OperatorNode *op = alloc_node<OperatorNode>();
+			op->op=OperatorNode::OP_ASSIGN;
+			op->arguments.push_back(id);
+			op->arguments.push_back(local_var->assign);
+			
+			branch->body->statements.push_front(op);
+			branch->body->statements.push_front(local_var);
+		}
+		
+		compiled_branch.body = branch->body;
+		
+		
+		p_match_statement->compiled_pattern_branches.push_back(compiled_branch);
+	}
+	
+}
+
 void GDParser::_parse_block(BlockNode *p_block,bool p_static) {
 
 	int indent_level = tab_level.back()->get();
@@ -2165,6 +2701,46 @@ void GDParser::_parse_block(BlockNode *p_block,bool p_static) {
 				}
 
 
+			} break;
+			case GDTokenizer::TK_CF_MATCH: {
+				
+				tokenizer->advance();
+				
+				MatchNode *match_node = alloc_node<MatchNode>();
+				
+				Node *val_to_match = _parse_and_reduce_expression(p_block, p_static);
+				
+				if (!val_to_match) {
+					if (_recover_from_completion()) {
+						break;
+					}
+					return;
+				}
+				
+				match_node->val_to_match = val_to_match;
+				
+				if (!_enter_indent_block()) {
+					_set_error("Expected indented pattern matching block after 'match'");
+					return;
+				}
+				
+				BlockNode *compiled_branches = alloc_node<BlockNode>();
+				compiled_branches->parent_block = p_block;
+				compiled_branches->parent_class = p_block->parent_class;
+				
+				p_block->sub_blocks.push_back(compiled_branches);
+				
+				_parse_pattern_block(compiled_branches, match_node->branches, p_static);
+				
+				_transform_match_statment(compiled_branches, match_node);
+				
+				ControlFlowNode *match_cf_node = alloc_node<ControlFlowNode>();
+				match_cf_node->cf_type = ControlFlowNode::CF_MATCH;
+				match_cf_node->match = match_node;
+				
+				p_block->statements.push_back(match_cf_node);
+				
+				_end_statement();
 			} break;
 			case GDTokenizer::TK_PR_ASSERT: {
 

modules/gdscript/gd_parser.h

@@ -259,6 +259,44 @@ public:
 		OperatorNode() { type=TYPE_OPERATOR; }
 	};
 	
+	
+	struct PatternNode : public Node {
+		
+		enum PatternType {
+			PT_CONSTANT,
+			PT_BIND,
+			PT_DICTIONARY,
+			PT_ARRAY,
+			PT_IGNORE_REST,
+			PT_WILDCARD
+		};
+		
+		PatternType pt_type;
+		
+		Node *constant;
+		StringName bind;
+		Map<ConstantNode*, PatternNode*> dictionary;
+		Vector<PatternNode*> array;
+		
+	};
+	
+	struct PatternBranchNode : public Node {
+		Vector<PatternNode*> patterns;
+		BlockNode *body;
+	};
+	
+	struct MatchNode : public Node {
+		Node *val_to_match;
+		Vector<PatternBranchNode*> branches;
+		
+		struct CompiledPatternBranch {
+			Node *compiled_pattern;
+			BlockNode *body;
+		};
+		
+		Vector<CompiledPatternBranch> compiled_pattern_branches;
+	};
+
 	struct ControlFlowNode : public Node {
 		enum CFType {
 			CF_IF,
@@ -267,7 +305,8 @@ public:
 			CF_SWITCH,
 			CF_BREAK,
 			CF_CONTINUE,
-			CF_RETURN
+			CF_RETURN,
+			CF_MATCH
 		};
 
 		CFType cf_type;
@@ -275,6 +314,8 @@ public:
 		BlockNode *body;
 		BlockNode *body_else;
 		
+		MatchNode *match;
+
 		ControlFlowNode *_else; //used for if
 		ControlFlowNode() { type=TYPE_CONTROL_FLOW; cf_type=CF_IF; body=NULL; body_else=NULL;}
 	};
@@ -452,6 +493,15 @@ private:
 	Node* _reduce_expression(Node *p_node,bool p_to_const=false);
 	Node* _parse_and_reduce_expression(Node *p_parent,bool p_static,bool p_reduce_const=false,bool p_allow_assign=false);
 
+	
+	
+	
+	PatternNode *_parse_pattern(bool p_static);
+	void _parse_pattern_block(BlockNode *p_block, Vector<PatternBranchNode*> &p_branches, bool p_static);
+	void _transform_match_statment(BlockNode *p_block, MatchNode *p_match_statement);
+	void _generate_pattern(PatternNode *p_pattern, Node *p_node_to_match, Node *&p_resulting_node, Map<StringName, Node*> &p_bindings);
+	
+	
 	void _parse_block(BlockNode *p_block,bool p_static);
 	void _parse_extends(ClassNode *p_class);
 	void _parse_class(ClassNode *p_class);

modules/gdscript/gd_script.cpp

@@ -1938,6 +1938,7 @@ void GDScriptLanguage::get_reserved_words(List<String> *p_words) const  {
 		"for",
 		"pass",
 		"return",
+		"match",
 		"while",
 		"remote",
 		"sync",

modules/gdscript/gd_tokenizer.cpp

@@ -85,6 +85,7 @@ const char* GDTokenizer::token_names[TK_MAX]={
 "continue",
 "pass",
 "return",
+"match",
 "func",
 "class",
 "extends",
@@ -894,6 +895,7 @@ void GDTokenizerText::_advance() {
 								{TK_CF_BREAK,"break"},
 								{TK_CF_CONTINUE,"continue"},
 								{TK_CF_RETURN,"return"},
+								{TK_CF_MATCH, "match"},
 								{TK_CF_PASS,"pass"},
 								{TK_SELF,"self"},
 								{TK_CONST_PI,"PI"},

modules/gdscript/gd_tokenizer.h

@@ -92,6 +92,7 @@ public:
 		TK_CF_CONTINUE,
 		TK_CF_PASS,
 		TK_CF_RETURN,
+		TK_CF_MATCH,
 		TK_PR_FUNCTION,
 		TK_PR_CLASS,
 		TK_PR_EXTENDS,