Implement function and variable codegen

common/addons/structure-terrascript-loader/build.gradle.kts

@@ -1,10 +1,12 @@
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
+import java.util.*
 
 version = version("1.1.0")
 
 dependencies {
     api("commons-io:commons-io:2.7")
     api("org.ow2.asm:asm:9.5")
+    api("org.ow2.asm:asm-commons:9.5")
     compileOnlyApi(project(":common:addons:manifest-addon-loader"))
     implementation("net.jafama", "jafama", Versions.Libraries.Internal.jafama)
     testImplementation("net.jafama", "jafama", Versions.Libraries.Internal.jafama)
@@ -18,44 +20,38 @@ tasks.named<ShadowJar>("shadowJar") {
 val astSourceSet = buildDir.resolve("generated/ast")
 val astPackage = astSourceSet.resolve("com/dfsek/terra/addons/terrascript/ast")
 
+data class ASTClass(val name: String, val imports: List<String>, val nodes: List<ASTNode>)
+
+data class ASTNode(val name: String, val constructorFields: List<Pair<String, String>>, val mutableFields: List<Pair<String, String>> = emptyList())
+
 // Auto generate AST classes rather than writing them by hand
 tasks.register("genTerrascriptAstClasses") {
+
+
     val packageName = astPackage.toRelativeString(astSourceSet).replace('/', '.')
-    fun generateClass(name: String, imports: List<String>, nodes: List<Pair<String, List<String>>>) {
+    fun generateClass(clazz: ASTClass) {
         val src = StringBuilder()
         src.appendLine("package $packageName;\n");
-        for (imprt in imports) src.appendLine("import $imprt;")
+        for (imprt in clazz.imports) src.appendLine("import $imprt;")
         src.appendLine("""
         import com.dfsek.terra.addons.terrascript.lexer.SourcePosition;
-        import com.dfsek.terra.addons.terrascript.Environment;
         
         /**
          * Auto-generated class via genTerrascriptAstClasses gradle task
          */
-        public abstract class $name {
+        public abstract class ${clazz.name} {
         
             public final SourcePosition position;
-            private Environment environment;
             
-            public $name(SourcePosition position) {
+            public ${clazz.name}(SourcePosition position) {
                 this.position = position;
             }
-            
-            public Environment getEnvironment() {
-                if (this.environment == null) throw new RuntimeException("Compilation bug! environment has not been set yet for AST node");
-                return environment;
-            }
-            
-            public void setEnvironment(Environment environment) {
-                if (this.environment != null) throw new RuntimeException("Compilation bug! environment has already been set for AST node and cannot be changed");
-                this.environment = environment;
-            }
         
             public interface Visitor<R> {
                 
         """.trimIndent())
-        for (node in nodes) {
-            src.appendLine("        R visit${node.first}$name(${node.first} ${name.toLowerCase()});")
+        for (node in clazz.nodes) {
+            src.appendLine("        R visit${node.name}${clazz.name}(${node.name} ${clazz.name.toLowerCase()});")
         }
 
         src.appendLine("""
@@ -65,79 +61,98 @@ tasks.register("genTerrascriptAstClasses") {
             |    public abstract <R> R accept(Visitor<R> visitor);
         """.trimMargin())
 
-        for (node in nodes) {
+        for (node in clazz.nodes) {
             src.appendLine()
             // Inner class declaration
-            src.appendLine("    public static class ${node.first} extends $name {\n")
+            src.appendLine("    public static class ${node.name} extends ${clazz.name} {\n")
 
             // Add fields
-            for (field in node.second) {
-                src.appendLine("        public final $field;")
+            for (field in node.constructorFields) {
+                src.appendLine("        public final ${field.second} ${field.first};")
+            }
+            for (field in node.mutableFields) {
+                src.appendLine("        private ${field.second} ${field.first};")
             }
             src.appendLine()
 
             // Add constructor
-            src.append("        public ${node.first}(")
-            for (field in node.second)
-                src.append("$field, ")
+            src.append("        public ${node.name}(")
+            for (field in node.constructorFields)
+                src.append("${field.second} ${field.first}, ")
             src.appendLine("SourcePosition position) {\n            super(position);")
-            for (field in node.second) {
-                val fieldName = field.split(' ').last()
-                src.appendLine("            this.$fieldName = $fieldName;")
+            for (field in node.constructorFields) {
+                src.appendLine("            this.${field.first} = ${field.first};")
+            }
+            src.appendLine("        }")
+
+            // Add getters and setters for mutable fields
+            for (field in node.mutableFields) {
+                src.appendLine("""
+                    |        
+                    |        public void set${field.first.capitalize()}(${field.second} value) {
+                    |            this.${field.first} = value;
+                    |        }
+                    |        
+                    |        public ${field.second} get${field.first.capitalize()}() {
+                    |            if (this.${field.first} == null) throw new RuntimeException("Compilation bug! Field ${field.first} has not been set yet");
+                    |            return this.${field.first};
+                    |        }
+                """.trimMargin())
             }
 
             src.appendLine("""
-                |        }
                 |        
                 |        @Override
                 |        public <R> R accept(Visitor<R> visitor) {
-                |            return visitor.visit${node.first}$name(this);
+                |            return visitor.visit${node.name}${clazz.name}(this);
                 |        }
                 |    }
             """.trimMargin())
         }
         src.appendLine("}")
-        val outputFile = astPackage.resolve("$name.java")
+        val outputFile = astPackage.resolve("${clazz.name}.java")
         outputFile.writeText(src.toString())
     }
 
     doLast {
         astSourceSet.deleteRecursively()
         astPackage.mkdirs()
-        generateClass("Expr", listOf(
+        generateClass(ASTClass("Expr", listOf(
             "com.dfsek.terra.addons.terrascript.Type",
             "com.dfsek.terra.addons.terrascript.parser.UnaryOperator",
             "com.dfsek.terra.addons.terrascript.parser.BinaryOperator",
+            "com.dfsek.terra.addons.terrascript.Environment.Symbol",
             "java.util.List",
         ),
         listOf(
-            Pair("Binary", listOf("Expr left", "BinaryOperator operator", "Expr right",)),
-            Pair("Grouping", listOf("Expr expression")),
-            Pair("Literal", listOf("Object value", "Type type")),
-            Pair("Unary", listOf("UnaryOperator operator", "Expr operand")),
-            Pair("Call", listOf("String identifier", "List<Expr> arguments")),
-            Pair("Variable", listOf("String identifier")),
-            Pair("Assignment", listOf("Variable lValue", "Expr rValue")),
-            Pair("Void", listOf()),
-        ))
-        generateClass("Stmt", listOf(
+            ASTNode("Binary", listOf("left" to "Expr", "operator" to "BinaryOperator", "right" to "Expr",), listOf("type" to "Type")),
+            ASTNode("Grouping", listOf("expression" to "Expr")),
+            ASTNode("Literal", listOf("value" to "Object", "type" to "Type")),
+            ASTNode("Unary", listOf("operator" to "UnaryOperator", "operand" to "Expr")),
+            ASTNode("Call", listOf("identifier" to "String", "arguments" to "List<Expr>"), listOf("symbol" to "Symbol.Function")),
+            ASTNode("Variable", listOf("identifier" to "String"), listOf("symbol" to "Symbol.Variable")),
+            ASTNode("Assignment", listOf("lValue" to "Variable", "rValue" to "Expr")),
+            ASTNode("Void", listOf()),
+        )))
+        generateClass(ASTClass("Stmt", listOf(
             "com.dfsek.terra.addons.terrascript.Type",
             "com.dfsek.terra.api.util.generic.pair.Pair",
+            "com.dfsek.terra.addons.terrascript.Environment.Symbol",
             "java.util.List",
         ),
         listOf(
-            Pair("Expression", listOf("Expr expression")),
-            Pair("Block", listOf("List<Stmt> statements")),
-            Pair("FunctionDeclaration", listOf("String identifier", "List<Pair<String, Type>> parameters", "Type type", "Block body")),
-            Pair("VariableDeclaration", listOf("Type type", "String identifier", "Expr value")),
-            Pair("Return", listOf("Expr value")),
-            Pair("If", listOf("Expr condition", "Block trueBody", "List<Pair<Expr, Block>> elseIfClauses", "Block elseBody")),
-            Pair("For", listOf("Stmt initializer", "Expr condition", "Expr incrementer", "Block body")),
-            Pair("While", listOf("Expr condition", "Block body")),
-            Pair("NoOp", listOf()),
-            Pair("Break", listOf()),
-            Pair("Continue", listOf()),
-        ))
+            ASTNode("Expression", listOf("expression" to "Expr")),
+            ASTNode("Block", listOf("statements" to "List<Stmt>")),
+            ASTNode("FunctionDeclaration", listOf("identifier" to "String", "parameters" to "List<Pair<String, Type>>", "type" to "Type", "body" to "Block"), listOf("symbol" to "Symbol.Function")),
+            ASTNode("VariableDeclaration", listOf("type" to "Type", "identifier" to "String", "value" to "Expr")),
+            ASTNode("Return", listOf("value" to "Expr"), listOf("type" to "Type")),
+            ASTNode("If", listOf("condition" to "Expr", "trueBody" to "Block", "elseIfClauses" to "List<Pair<Expr, Block>>", "elseBody" to "Block")),
+            ASTNode("For", listOf("initializer" to "Stmt", "condition" to "Expr", "incrementer" to "Expr", "body" to "Block")),
+            ASTNode("While", listOf("condition" to "Expr", "body" to "Block")),
+            ASTNode("NoOp", listOf()),
+            ASTNode("Break", listOf()),
+            ASTNode("Continue", listOf()),
+        )))
     }
 }
 

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/Environment.java

@@ -1,14 +1,23 @@
 package com.dfsek.terra.addons.terrascript;
 
 import javax.annotation.Nullable;
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 
 import com.dfsek.terra.addons.terrascript.Environment.ScopeException.NonexistentSymbolException;
 import com.dfsek.terra.addons.terrascript.Environment.ScopeException.SymbolAlreadyExistsException;
 import com.dfsek.terra.addons.terrascript.Environment.ScopeException.SymbolTypeMismatchException;
 import com.dfsek.terra.addons.terrascript.Environment.Symbol.Function;
 import com.dfsek.terra.addons.terrascript.Environment.Symbol.Variable;
+import com.dfsek.terra.addons.terrascript.codegen.TerraScript;
 import com.dfsek.terra.api.util.generic.pair.Pair;
 
 
@@ -18,7 +27,7 @@ public class Environment {
     
     private final boolean canAccessOuterVariables;
     
-    private final HashMap<String, Symbol> symbolTable = new HashMap<>();
+    private final Map<String, Symbol> symbolTable = new HashMap<>();
     
     private final boolean inLoop;
     
@@ -26,6 +35,13 @@ public class Environment {
         this.outer = outer;
         this.canAccessOuterVariables = canAccessOuterVariables;
         this.inLoop = inLoop;
+        // Populate symbol tables with built-in Java implemented methods
+        TerraScript.BUILTIN_FUNCTIONS.forEach((name, method) -> symbolTable
+                .put(name,
+                     new Function(
+                             Type.from(method.getReturnType()).orElseThrow(() -> new RuntimeException("")),
+                             // Map Java classes to TerraScript types
+                             IntStream.range(0, method.getParameterCount()).mapToObj(i -> Pair.of("param" + i, Type.from(method.getParameterTypes()[i]).orElseThrow(() -> new RuntimeException("")))).toList())));
     }
     
     public static Environment global() {

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/Type.java

@@ -1,9 +1,30 @@
 package com.dfsek.terra.addons.terrascript;
 
+import java.util.Optional;
+
+
 // TODO - Make not enum
 public enum Type {
     NUMBER,
     STRING,
     BOOLEAN,
-    VOID,
+    VOID;
+    
+    public java.lang.reflect.Type javaType() {
+        return switch(this) {
+            case NUMBER -> double.class;
+            case STRING -> String.class;
+            case BOOLEAN -> boolean.class;
+            case VOID -> void.class;
+        };
+    }
+    
+    public static Optional<Type> from(Class<?> clazz) {
+        return Optional.ofNullable(
+                clazz == double.class ? NUMBER :
+                clazz == String.class ? STRING :
+                clazz == boolean.class ? BOOLEAN :
+                clazz == void.class ? VOID :
+                null);
+    }
 }

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/codegen/TerraScript.java

@@ -0,0 +1,19 @@
+package com.dfsek.terra.addons.terrascript.codegen;
+
+import java.lang.reflect.Method;
+import java.util.HashMap;
+import java.util.Map;
+
+
+public interface TerraScript {
+    
+    void execute();
+    
+    Map<String, Method> BUILTIN_FUNCTIONS = new HashMap<>() {{
+        try {
+            put("print", System.out.getClass().getMethod("println", String.class));
+        } catch(NoSuchMethodException e) {
+            throw new RuntimeException(e);
+        }
+    }};
+}

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/codegen/asm/TerraScript.java

@@ -1,7 +0,0 @@
-package com.dfsek.terra.addons.terrascript.codegen.asm;
-
-public interface TerraScript {
-    
-    void execute();
-    
-}

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/codegen/asm/TerraScriptClassGenerator.java

@@ -1,5 +1,7 @@
 package com.dfsek.terra.addons.terrascript.codegen.asm;
 
+import com.dfsek.terra.addons.terrascript.Environment.Symbol;
+import com.dfsek.terra.addons.terrascript.Type;
 import com.dfsek.terra.addons.terrascript.ast.Expr;
 import com.dfsek.terra.addons.terrascript.ast.Expr.Assignment;
 import com.dfsek.terra.addons.terrascript.ast.Expr.Binary;
@@ -22,24 +24,26 @@ import com.dfsek.terra.addons.terrascript.ast.Stmt.Return;
 import com.dfsek.terra.addons.terrascript.ast.Stmt.VariableDeclaration;
 import com.dfsek.terra.addons.terrascript.ast.Stmt.While;
 
+import com.dfsek.terra.addons.terrascript.codegen.TerraScript;
+import com.dfsek.terra.addons.terrascript.util.ASMUtil;
+import com.dfsek.terra.api.util.generic.pair.Pair;
+
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.ClassVisitor;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Label;
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.commons.LocalVariablesSorter;
 
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 import static com.dfsek.terra.addons.terrascript.util.ASMUtil.dynamicName;
-import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
-import static org.objectweb.asm.Opcodes.ALOAD;
-import static org.objectweb.asm.Opcodes.INVOKESPECIAL;
-import static org.objectweb.asm.Opcodes.IOR;
-import static org.objectweb.asm.Opcodes.RETURN;
-
 
 public class TerraScriptClassGenerator {
     
@@ -55,6 +59,12 @@ public class TerraScriptClassGenerator {
         this.debugPath = debugPath;
     }
     
+    /**
+     *
+     * @param root Assumed to be semantically correct
+     * @return Generated TerraScript instance
+     * @throws IOException
+     */
     public TerraScript generate(Block root) throws IOException {
         String targetClassName = dynamicName(TARGET_CLASS);
         String generatedClassName = targetClassName + "_GENERATED_" + generationCount;
@@ -65,11 +75,11 @@ public class TerraScriptClassGenerator {
         classWriter.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, generatedClassName, null, "java/lang/Object", new String[]{ targetClassName });
        
         // Generate constructor method
-        MethodVisitor constructor = classWriter.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
+        MethodVisitor constructor = classWriter.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
         constructor.visitCode();
-        constructor.visitVarInsn(ALOAD, 0); // Put this reference on stack
-        constructor.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
-        constructor.visitInsn(RETURN); // Void return
+        constructor.visitVarInsn(Opcodes.ALOAD, 0); // Put this reference on stack
+        constructor.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
+        constructor.visitInsn(Opcodes.RETURN); // Void return
         constructor.visitMaxs(0, 0);
         constructor.visitEnd();
         
@@ -79,16 +89,14 @@ public class TerraScriptClassGenerator {
         MethodExtractor extractor = new MethodExtractor(methodName);
         new ClassReader(targetClassName).accept(extractor, 0);
         String description = extractor.methodDescription;
-        MethodVisitor execute = classWriter.visitMethod(Opcodes.ACC_PUBLIC, methodName, description, null, null);
-        execute.visitCode(); // Start method body
-        
-        execute.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
-        new BytecodeGenerator(execute).visitBlockStmt(root);
-        execute.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Z)V", false);
-        
-        execute.visitInsn(RETURN);
-        execute.visitMaxs(0, 0);
-        execute.visitEnd();
+        int exeAcc = Opcodes.ACC_PUBLIC;
+        MethodVisitor executeMethod = classWriter.visitMethod(exeAcc, methodName, description, null, null);
+        executeMethod.visitCode(); // Start method body
+        new MethodBytecodeGenerator(classWriter, generatedClassName, executeMethod, exeAcc, description).generate(root); // Generate bytecode
+        // Finish up method
+        executeMethod.visitInsn(Opcodes.RETURN);
+        executeMethod.visitMaxs(0, 0);
+        executeMethod.visitEnd();
         
         // Finished generating class
         classWriter.visitEnd();
@@ -119,12 +127,31 @@ public class TerraScriptClassGenerator {
         }
     }
     
-    private static class BytecodeGenerator implements Stmt.Visitor<Void>, Expr.Visitor<Void> {
+    private static class MethodBytecodeGenerator implements Stmt.Visitor<Void>, Expr.Visitor<Void> {
+        
+        private final ClassWriter classWriter;
+        
+        private final String className;
         
         private final MethodVisitor method;
         
-        public BytecodeGenerator(MethodVisitor method) {
+        private final String descriptor;
+        
+        private final LocalVariablesSorter lvs;
+        
+        private final Map<String, Integer> lvTable = new HashMap<>();
+        
+        public MethodBytecodeGenerator(ClassWriter classWriter, String className, MethodVisitor method, int access, String descriptor) {
+            this.classWriter = classWriter;
+            this.className = className;
             this.method = method;
+            this.descriptor = descriptor;
+            this.lvs = new LocalVariablesSorter(access, descriptor, method);
+        }
+        
+        public void generate(Block root) {
+            this.visitBlockStmt(root);
+            
         }
         
         @Override
@@ -181,7 +208,14 @@ public class TerraScriptClassGenerator {
                     method.visitInsn(Opcodes.ICONST_0);
                     method.visitLabel(finished);
                 }
-                case ADD -> method.visitInsn(Opcodes.DADD);
+                case ADD -> {
+                    switch(expr.getType()) {
+                        case NUMBER -> method.visitInsn(Opcodes.DADD);
+                        // TODO - Optimize string concatenation
+                        case STRING -> method.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/String", "concat", "(Ljava/lang/String;)Ljava/lang/String;", false);
+                        default -> throw new RuntimeException("Could not generate bytecode for ADD binary operator returning type " + expr.getType());
+                    }
+                }
                 case SUBTRACT -> method.visitInsn(Opcodes.DSUB);
                 case MULTIPLY -> method.visitInsn(Opcodes.DMUL);
                 case DIVIDE -> method.visitInsn(Opcodes.DDIV);
@@ -209,16 +243,43 @@ public class TerraScriptClassGenerator {
         
         @Override
         public Void visitCallExpr(Call expr) {
+            Symbol.Function function = expr.getSymbol();
+            if (TerraScript.BUILTIN_FUNCTIONS.containsKey(expr.identifier)) {
+                if (expr.identifier.equals("print")) { // TODO - remove quick dirty print function call
+                    method.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
+                    expr.arguments.get(0).accept(this);
+                    method.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
+                }
+                return null;
+            }
+            expr.arguments.forEach(a -> a.accept(this));
+            List<Type> parameters = function.parameters.stream().map(Pair::getRight).toList();
+            method.visitMethodInsn(Opcodes.INVOKESTATIC, className, expr.identifier, getFunctionDescriptor(parameters, function.type), false);
             return null;
         }
         
         @Override
         public Void visitVariableExpr(Variable expr) {
+            Type varType = expr.getSymbol().type;
+            method.visitVarInsn(switch(varType) {
+                case NUMBER -> Opcodes.DLOAD;
+                case STRING -> Opcodes.ALOAD;
+                case BOOLEAN -> Opcodes.ILOAD;
+                default -> throw new RuntimeException("Unable to load local variable, unknown parameter type '" + varType + "'");
+            }, lvTable.get(expr.identifier));
             return null;
         }
         
         @Override
         public Void visitAssignmentExpr(Assignment expr) {
+            expr.rValue.accept(this);
+            Type type = expr.lValue.getSymbol().type;
+            method.visitVarInsn(switch(type) {
+                case NUMBER -> Opcodes.DSTORE;
+                case STRING -> Opcodes.ASTORE;
+                case BOOLEAN -> Opcodes.ISTORE;
+                default -> throw new RuntimeException("Unable to assign local variable, unknown parameter type '" + type + "'");
+            }, lvTable.get(expr.lValue.identifier));
             return null;
         }
         
@@ -239,18 +300,77 @@ public class TerraScriptClassGenerator {
             return null;
         }
         
+        private String getFunctionDescriptor(List<Type> parameters, Type returnType) {
+            StringBuilder sb = new StringBuilder().append("(");
+            parameters.stream().map(p -> switch (p) {
+                case NUMBER -> "D";
+                case STRING -> "Ljava/lang/String;";
+                case BOOLEAN -> "Z";
+                default -> throw new RuntimeException("Unable to generate method descriptor, unknown parameter type '" + p + "'");
+            }).forEach(sb::append);
+            sb.append(")");
+            sb.append(switch (returnType) {
+                case NUMBER -> "D";
+                case STRING -> "Ljava/lang/String;";
+                case BOOLEAN -> "Z";
+                case VOID -> "V";
+            });
+            return sb.toString();
+        }
+        
         @Override
         public Void visitFunctionDeclarationStmt(FunctionDeclaration stmt) {
+            int access = Opcodes.ACC_PRIVATE | Opcodes.ACC_STATIC;
+            List<Type> parameterTypes = stmt.parameters.stream().map(Pair::getRight).toList();
+            MethodVisitor method = classWriter.visitMethod(access, stmt.identifier, getFunctionDescriptor(parameterTypes, stmt.type), null, null);
+            
+            method.visitCode(); // Start method body
+            
+            MethodBytecodeGenerator funcGenerator = new MethodBytecodeGenerator(classWriter, className, method, access, descriptor);
+            
+            // Add local variable indexes for each parameter
+            int lvidx = 0;
+            for (Pair<String, Type> parameter : stmt.parameters) {
+                funcGenerator.lvTable.put(parameter.getLeft(), lvidx);
+                lvidx += switch(parameter.getRight()) {
+                    case NUMBER -> 2;
+                    case STRING, BOOLEAN -> 1;
+                    default -> throw new RuntimeException("Unable to register local variable index for parameter, unknown parameter type '" + parameter.getRight() + "'");
+                };
+            }
+            
+            // Generate method bytecode
+            funcGenerator.generate(stmt.body);
+            
+            // Finish up
+            method.visitInsn(Opcodes.RETURN);
+            method.visitMaxs(0, 0);
+            method.visitEnd();
+            
             return null;
         }
         
         @Override
         public Void visitVariableDeclarationStmt(VariableDeclaration stmt) {
+            stmt.value.accept(this);
+            lvTable.put(stmt.identifier, lvs.newLocal(ASMUtil.tsTypeToAsmType(stmt.type)));
+            method.visitVarInsn(switch(stmt.type) {
+                case NUMBER -> Opcodes.DSTORE;
+                case STRING -> Opcodes.ASTORE;
+                case BOOLEAN -> Opcodes.ISTORE;
+                default -> throw new RuntimeException("Unable to declare local variable, unknown parameter type '" + stmt.type + "'");
+            }, lvTable.get(stmt.identifier));
             return null;
         }
         
         @Override
         public Void visitReturnStmt(Return stmt) {
+            stmt.value.accept(this);
+            switch(stmt.getType()) {
+                case NUMBER -> method.visitInsn(Opcodes.DRETURN);
+                case STRING -> method.visitInsn(Opcodes.ARETURN);
+                case BOOLEAN -> method.visitInsn(Opcodes.IRETURN);
+            }
             return null;
         }
         

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/semanticanalysis/FunctionReferenceAnalyzer.java

@@ -63,7 +63,7 @@ public class FunctionReferenceAnalyzer implements Expr.Visitor<Void>, Stmt.Visit
     public Void visitCallExpr(Call expr) {
         String id = expr.identifier;
         try {
-            expr.getEnvironment().getFunction(id);
+            expr.getSymbol();
         } catch(NonexistentSymbolException e) {
             errorHandler.add(
                     new UndefinedReferenceException("No function by the name '" + id + "' is defined in this scope", expr.position));

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/semanticanalysis/ScopeAnalyzer.java

@@ -60,7 +60,7 @@ public class ScopeAnalyzer implements Visitor<Void>, Stmt.Visitor<Void> {
     
     @Override
     public Void visitCallExpr(Call expr) {
-        expr.setEnvironment(currentScope);
+        expr.setSymbol(currentScope.getFunction(expr.identifier));
         expr.arguments.forEach(e -> e.accept(this));
         return null;
     }
@@ -76,7 +76,7 @@ public class ScopeAnalyzer implements Visitor<Void>, Stmt.Visitor<Void> {
         } catch(SymbolTypeMismatchException e) {
             errorHandler.add(new ParseException("Identifier '" + id + "' is not defined as a variable", expr.position));
         }
-        expr.setEnvironment(currentScope);
+        expr.setSymbol(currentScope.getVariable(expr.identifier));
         return null;
     }
     
@@ -136,7 +136,6 @@ public class ScopeAnalyzer implements Visitor<Void>, Stmt.Visitor<Void> {
             errorHandler.add(new IdentifierAlreadyDeclaredException("Name '" + stmt.identifier + "' is already defined in this scope",
                                                                     stmt.position));
         }
-        stmt.setEnvironment(currentScope);
         return null;
     }
     

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/semanticanalysis/TypeChecker.java

@@ -51,8 +51,14 @@ public class TypeChecker implements Visitor<Type>, Stmt.Visitor<Type> {
                 yield Type.BOOLEAN;
             }
             case ADD -> {
-                if(left == Type.NUMBER && right == Type.NUMBER) yield Type.NUMBER;
-                if(left == Type.STRING || right == Type.STRING) yield Type.STRING;
+                if(left == Type.NUMBER && right == Type.NUMBER) {
+                    expr.setType(Type.NUMBER);
+                    yield Type.NUMBER;
+                }
+                if(left == Type.STRING || right == Type.STRING) {
+                    expr.setType(Type.STRING);
+                    yield Type.STRING;
+                }
                 throw new RuntimeException("Addition operands must be either both numbers, or one of type string");
             }
             case SUBTRACT, MULTIPLY, DIVIDE, MODULO -> {
@@ -92,10 +98,10 @@ public class TypeChecker implements Visitor<Type>, Stmt.Visitor<Type> {
     public Type visitCallExpr(Call expr) {
         String id = expr.identifier;
         
-        Environment.Symbol.Function signature = expr.getEnvironment().getFunction(id);
+        Environment.Symbol.Function signature = expr.getSymbol();
         
         List<Type> argumentTypes = expr.arguments.stream().map(a -> a.accept(this)).toList();
-        List<Pair<String, Type>> parameters = signature.parameters;
+        List<Type> parameters = signature.parameters.stream().map(Pair::getRight).toList();
         
         if(argumentTypes.size() != parameters.size())
             errorHandler.add(new ParseException(
@@ -103,7 +109,7 @@ public class TypeChecker implements Visitor<Type>, Stmt.Visitor<Type> {
                     " arguments", expr.position));
         
         for(int i = 0; i < parameters.size(); i++) {
-            Type expectedType = parameters.get(i).getRight();
+            Type expectedType = parameters.get(i);
             Type providedType = argumentTypes.get(i);
             if(expectedType != providedType)
                 errorHandler.add(new InvalidTypeException(
@@ -116,7 +122,7 @@ public class TypeChecker implements Visitor<Type>, Stmt.Visitor<Type> {
     
     @Override
     public Type visitVariableExpr(Variable expr) {
-        return expr.getEnvironment().getVariable(expr.identifier).type;
+        return expr.getSymbol().type;
     }
     
     @Override
@@ -182,7 +188,7 @@ public class TypeChecker implements Visitor<Type>, Stmt.Visitor<Type> {
     
     @Override
     public Type visitReturnStmt(Stmt.Return stmt) {
-        stmt.value.accept(this);
+        stmt.setType(stmt.value.accept(this));
         return Type.VOID;
     }
     

common/addons/structure-terrascript-loader/src/main/java/com/dfsek/terra/addons/terrascript/util/ASMUtil.java

@@ -1,5 +1,8 @@
 package com.dfsek.terra.addons.terrascript.util;
 
+import com.dfsek.terra.addons.terrascript.Type;
+
+
 public class ASMUtil {
     
     /**
@@ -10,4 +13,8 @@ public class ASMUtil {
     public static String dynamicName(Class<?> clazz) {
         return clazz.getCanonicalName().replace('.', '/');
     }
+    
+    public static org.objectweb.asm.Type tsTypeToAsmType(Type type) {
+        return org.objectweb.asm.Type.getType((Class<?>) type.javaType());
+    }
 }

common/addons/structure-terrascript-loader/src/test/java/codegen/CodeGenTest.java

@@ -0,0 +1,77 @@
+package codegen;
+
+import com.dfsek.terra.addons.terrascript.ErrorHandler;
+import com.dfsek.terra.addons.terrascript.ast.Stmt.Block;
+import com.dfsek.terra.addons.terrascript.codegen.TerraScript;
+import com.dfsek.terra.addons.terrascript.codegen.asm.TerraScriptClassGenerator;
+import com.dfsek.terra.addons.terrascript.lexer.Lexer;
+import com.dfsek.terra.addons.terrascript.parser.Parser;
+import com.dfsek.terra.addons.terrascript.semanticanalysis.SemanticAnalyzer;
+
+import org.junit.jupiter.api.Test;
+
+public class CodeGenTest {
+    
+    @Test
+    public void test() {
+        testValid("""
+                  fun retNum(): num {
+                      return 3 + 3;
+                  }
+                  
+                  fun retBool(): bool {
+                      return true;
+                  }
+                  
+                  fun concatThree(a: str, b: str, c: str): str {
+                      return a + b + c;
+                  }
+                  
+                  fun retStr(): str {
+                      fun concatTwo(a: str, b: str): str {
+                          return a + b;
+                      }
+                      str hello = "Hell";
+                      hello = concatTwo(hello, "o");
+                      str world = "world!";
+                      return concatThree(hello, " ", world);
+                  }
+                  
+                  fun takesArgs(a: str, b: num, c: bool): str {
+                      return a;
+                  }
+                  
+                  fun doStuff(a: str, b: str, c: bool) {
+                      print("Doing stuff");
+                      if (c) {
+                          print(concatThree(a, " ", b));
+                      } else {
+                          print("c is false");
+                      }
+                  }
+                  
+                  num a = 1;
+                  num b = 2;
+                  str e = "test";
+                  
+                  retNum();
+                  bool bln = true;
+              
+                  print(takesArgs("test", 3, true));
+                  print(retStr());
+                  
+                  doStuff("Ay0o", "world", true);
+                  """);
+    }
+    
+    private void testValid(String validSource) {
+        try {
+            Block script = Parser.parse(new Lexer(validSource).analyze());
+            SemanticAnalyzer.analyze(script, new ErrorHandler());
+            TerraScript ts = new TerraScriptClassGenerator("./build/codegentest").generate(script);
+            ts.execute();
+        } catch(Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+}