diff --git a/src/parser.cpp b/src/parser.cpp
index 5415798..4a2718d 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -21,7 +21,7 @@ namespace Solstice {
                     if (variables.find(i.outputId) != variables.end()) {
                         return variables[i.outputId];
                     } else {
-                        Error::syntaxError("Unknown variable", i.line, i.lineContent);
+                        Error::syntaxError("Unknown variable " + i.outputId, i.line, i.lineContent);
                     }
                     break;
                 }
@@ -55,6 +55,63 @@ namespace Solstice {
                     return "int";
                     break;
                 }
+                case SolNodeType::FunctionCall: {
+                    if (i.children[0].outputId == "input") {
+                        if (i.children.size() > 1) {
+                            ensure(i.children[1], "string", "input function argument");
+                        }
+                        return "string";
+                    }
+                    
+                    std::string funcName = i.children[0].outputId;
+                    if (variables.find(funcName) == variables.end()) {
+                        Error::syntaxError("Unknown function " + funcName, i.line, i.lineContent);
+                    }
+                    std::string signature = variables[funcName];
+                    
+                    // Parse signature: fun(arg1, arg2) retType
+                    if (signature.rfind("fun(", 0) != 0) {
+                         // Not a function signature, maybe it's a variable being called?
+                         Error::typingError(funcName + " is not a function", i.line, i.lineContent);
+                    }
+
+                    size_t endParen = signature.find(')');
+                    if (endParen == std::string::npos) {
+                        Error::typingError("Invalid function signature for " + funcName, i.line, i.lineContent);
+                    }
+
+                    std::string argsStr = signature.substr(4, endParen - 4);
+                    std::string retType = signature.substr(endParen + 2); // skip ") "
+
+                    std::vector<std::string> expectedArgs;
+                    if (!argsStr.empty()) {
+                        size_t start = 0;
+                        size_t end = argsStr.find(", ");
+                        while (end != std::string::npos) {
+                            expectedArgs.push_back(argsStr.substr(start, end - start));
+                            start = end + 2;
+                            end = argsStr.find(", ", start);
+                        }
+                        expectedArgs.push_back(argsStr.substr(start));
+                    }
+
+                    // Check arguments
+                    // children[0] is function name, children[1..] are args
+                    if (i.children.size() - 1 != expectedArgs.size()) {
+                        Error::typingError("Expected " + std::to_string(expectedArgs.size()) + " arguments for " + funcName + ", got " + std::to_string(i.children.size() - 1), i.line, i.lineContent);
+                        return "none";
+                    }
+
+                    for (size_t k = 0; k < expectedArgs.size(); ++k) {
+                        std::string argType = checkNodeReturnType(i.children[k + 1]);
+                        if (argType != expectedArgs[k]) {
+                            Error::typingError("Expected argument " + std::to_string(k + 1) + " of " + funcName + " to be " + expectedArgs[k] + ", got " + argType, i.children[k + 1].line, i.children[k + 1].lineContent);
+                        }
+                    }
+
+                    return retType;
+                    break;
+                }
                 case SolNodeType::Puts:
                 case SolNodeType::If:
                 case SolNodeType::While:
@@ -602,6 +659,7 @@ namespace Solstice {
                         break;
                     }
                     case SolNodeType::FunctionCall: {
+                        checkNodeReturnType(*this);
                         // Take care of in built functions
                         // This will be removed when inline ground is added
                         if (children[0].outputId == "input") {
@@ -635,6 +693,10 @@ namespace Solstice {
                         break;
                     }
                     case SolNodeType::Return: {
+                        std::string retType = checkNodeReturnType(children[0]);
+                        if (currentFunctionRetType != "" && retType != currentFunctionRetType) {
+                             Error::typingError("Expected return type " + currentFunctionRetType + " but got " + retType, children[0].line, children[0].lineContent);
+                        }
                         SolGroundCodeBlock codeBlock;
                         GroundInstruction returnInstruction = groundCreateInstruction(RETURN);
                         groundAddReferenceToInstruction(&returnInstruction, groundCreateReference(VALREF, children[0].outputId.data()));
@@ -654,21 +716,34 @@ namespace Solstice {
                             strcpy(retType, function.returnType.c_str());
                             groundAddReferenceToInstruction(&inst, groundCreateReference(FNREF, fnName));
                             groundAddReferenceToInstruction(&inst, groundCreateReference(TYPEREF, retType));
+                            
+                            // Scope Management
                             auto variablebackup = variables;
-                            variables.clear();
+                            std::string oldRetType = currentFunctionRetType;
+                            
+                            variables.clear(); 
+                            currentFunctionRetType = function.returnType;
+
                             for (auto& pair : function.parameters) {
                                 groundAddReferenceToInstruction(&inst, groundCreateReference(TYPEREF, pair.second.data()));
                                 groundAddReferenceToInstruction(&inst, groundCreateReference(DIRREF, pair.first.data()));
-                                variables[pair.second] = pair.first;
+                                variables[pair.first] = pair.second; // Correctly map Name -> Type
                             }
-                            variables = variablebackup;
+                            
                             codeBlock.code.push_back(inst);
                             code.push_back(codeBlock);
                             codeBlock.code.clear();
+                            
+                            // Generate body code with local variables visible
                             auto childCode = function.content->generateCode();
                             code.insert(code.end(), childCode.begin(), childCode.end());
+                            
                             codeBlock.code.push_back(groundCreateInstruction(ENDFUN));
                             code.push_back(codeBlock);
+                            
+                            // Restore Scope
+                            variables = variablebackup;
+                            currentFunctionRetType = oldRetType;
                         }
                         break;
                     }