Fix String adding without needing to add trait machinery (yet).

Cargo.lock

@@ -119,6 +119,13 @@ dependencies = [
  "dvm-lib",
 ]
 
+[[package]]
+name = "dm-core-impl"
+version = "0.1.0"
+dependencies = [
+ "dvm-lib",
+]
+
 [[package]]
 name = "dm-std-lib"
 version = "0.1.0"

Cargo.toml

@@ -1,3 +1,3 @@
 [workspace]
 resolver = "3"
-members = ["dm", "dm-std-lib", "dmc-lib", "dvm-lib", "e2e-tests"]
+members = ["dm", "dm-core-impl", "dm-std-lib", "dmc-lib", "dvm-lib", "e2e-tests"]

dm-core-impl/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "dm-core-impl"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+dvm-lib = { path = "../dvm-lib" }

dm-core-impl/src/error.rs

@@ -0,0 +1,31 @@
+use std::error::Error;
+use std::fmt::{Display, Formatter};
+
+#[derive(Debug)]
+pub struct IllegalArgumentError {
+    message: String,
+}
+
+// Eventually we'll want support for source position, so we can highlight which argument(s)
+// are wrong
+impl IllegalArgumentError {
+    pub fn wrong_type(expected: &str, found: &str) -> Self {
+        Self {
+            message: format!("Expected {} but found {}", expected, found),
+        }
+    }
+
+    pub fn wrong_number(expected: usize, found: usize) -> Self {
+        Self {
+            message: format!("Expected {} argument(s) but found {}", expected, found),
+        }
+    }
+}
+
+impl Display for IllegalArgumentError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "IllegalArgumentError: {}", self.message)
+    }
+}
+
+impl Error for IllegalArgumentError {}

dm-core-impl/src/lib.rs

@@ -0,0 +1,7 @@
+mod error;
+pub mod print;
+pub mod string;
+mod util;
+
+pub use print::*;
+pub use string::*;

dm-core-impl/src/print.rs

@@ -0,0 +1,56 @@
+use crate::error::IllegalArgumentError;
+use dvm_lib::vm::value::Value;
+use std::error::Error;
+use std::ops::Deref;
+
+pub fn core_print(args: &[Value]) -> Result<Value, Box<dyn Error>> {
+    match args.get(0) {
+        None => Err(Box::new(IllegalArgumentError::wrong_number(1, 0))),
+        Some(msg) => {
+            match msg {
+                Value::Object(object) => {
+                    todo!("printing objects")
+                }
+                Value::Int(i) => {
+                    print!("{}", i);
+                }
+                Value::Double(d) => {
+                    print!("{}", d);
+                }
+                Value::String(s) => {
+                    print!("{}", s.deref());
+                }
+                Value::Null => {
+                    print!("Null");
+                }
+            }
+            Ok(Value::Null)
+        }
+    }
+}
+
+pub fn core_println(args: &[Value]) -> Result<Value, Box<dyn Error>> {
+    match args.get(0) {
+        None => Err(Box::new(IllegalArgumentError::wrong_number(1, 0))),
+        Some(msg) => {
+            match msg {
+                Value::Object(object) => {
+                    todo!("printing objects")
+                }
+                Value::Int(i) => {
+                    println!("{}", i);
+                }
+                Value::Double(d) => {
+                    println!("{}", d);
+                }
+                Value::String(s) => {
+                    println!("{}", s.deref());
+                }
+                Value::Null => {
+                    print!("Null");
+                }
+            }
+            Ok(Value::Null)
+        }
+    }
+}

dm-core-impl/src/string.rs

@@ -0,0 +1,21 @@
+use crate::error::IllegalArgumentError;
+use crate::util::value_to_variant_name;
+use dvm_lib::vm::value::Value;
+use std::error::Error;
+
+pub fn core_string_len(args: &[Value]) -> Result<Value, Box<dyn Error>> {
+    let this = args.get(0);
+    match this {
+        None => Err(Box::new(IllegalArgumentError::wrong_number(1, 0))),
+        Some(this) => match this {
+            Value::String(s) => {
+                let len: i64 = s.len().try_into()?;
+                todo!("Long Values")
+            }
+            _ => Err(Box::new(IllegalArgumentError::wrong_type(
+                "String",
+                value_to_variant_name(this),
+            ))),
+        },
+    }
+}

dm-core-impl/src/util.rs

@@ -0,0 +1,11 @@
+use dvm_lib::vm::value::Value;
+
+pub fn value_to_variant_name(value: &Value) -> &'static str {
+    match value {
+        Value::Object(_) => "Object", // todo: lookup class
+        Value::Int(_) => "Int",
+        Value::Double(_) => "Double",
+        Value::String(_) => "String",
+        Value::Null => "Null",
+    }
+}

dm-core/src/lib.dm

@@ -0,0 +1,6 @@
+mod ops
+mod print
+mod string
+
+pub use print::*
+pub use string::*

dm-core/src/ops.dm

@@ -0,0 +1,6 @@
+pub trait Add
+    type Right = Self
+    type Result = Self
+
+    fn add(right: Self::Right) -> Self::Result
+end

dm-core/src/print.dm

@@ -0,0 +1,3 @@
+pub extern fn print(msg: Any) -> Void
+
+pub extern fn println(msg: Any) -> Void

dm-core/src/string.dm

@@ -0,0 +1,5 @@
+pub extern class String
+    pub extern fn len() -> Long
+end
+
+intrinsic impl<T> Add<Right = T> for String end

dm/src/repl.rs

@@ -4,11 +4,14 @@ use codespan_reporting::term::{Config, WriteStyle, emit_to_write_style};
 use dmc_lib::SyntheticFunctionSession;
 use dmc_lib::constants_table::ConstantsTable;
 use dmc_lib::diagnostic::Diagnostics;
+use dmc_lib::intrinsics::add_primitive_symbols_and_type_infos;
 use dmc_lib::parser::parse_statement;
 use dvm_lib::vm::constant::{Constant, StringConstant};
 use dvm_lib::vm::function::Function;
 use dvm_lib::vm::operand::Operand;
+use dvm_lib::vm::value::Value;
 use dvm_lib::vm::{CallStack, DvmContext, loop_instructions, prepare_for_instruction_loop};
+use std::error::Error;
 use std::io::{BufRead, Write};
 
 pub fn repl(
@@ -26,13 +29,26 @@ pub fn repl(
     let mut session = SyntheticFunctionSession::new("__repl");
 
     let analysis_context = session.ctx_mut();
-    analysis_context.push_scope("__repl_root_scope");
+    let root_scope_id = analysis_context.push_scope("__repl_root_scope");
     analysis_context.push_scope("__repl_function_scope");
     analysis_context.push_scope("__repl_body_scope");
 
+    add_primitive_symbols_and_type_infos(analysis_context, root_scope_id);
+
     let mut constants_table = ConstantsTable::new();
 
     let mut dvm_context = DvmContext::new();
+
+    // todo: move this to a core impl crate
+    fn core_string_len(args: &[Value]) -> Result<Value, Box<dyn Error>> {
+        let this = args[0].unwrap_string();
+        let len = this.len();
+        Ok(Value::Int(len as i32))
+    }
+    dvm_context
+        .platform_functions_mut()
+        .insert("core::String::len".into(), core_string_len);
+
     let mut repl_fn_stack_locals: Vec<Operand> = Vec::new();
 
     'repl: loop {

dmc-lib/src/ast/expression.rs

@@ -5,6 +5,7 @@ use crate::ast::double_literal::DoubleLiteral;
 use crate::ast::identifier::Identifier;
 use crate::ast::integer_literal::IntegerLiteral;
 use crate::ast::negative_expression::NegativeExpression;
+use crate::ast::path::Path;
 use crate::ast::string_literal::StringLiteral;
 use crate::source_range::SourceRange;
 
@@ -12,6 +13,7 @@ pub enum Expression {
     Binary(BinaryExpression),
     Negative(NegativeExpression),
     Call(Call),
+    Path(Path),
     Identifier(Identifier),
     Integer(IntegerLiteral),
     Double(DoubleLiteral),
@@ -24,6 +26,7 @@ impl Expression {
             Expression::Binary(binary_expression) => binary_expression.node_id(),
             Expression::Negative(negative_expression) => negative_expression.node_id(),
             Expression::Call(call) => call.node_id(),
+            Expression::Path(path) => path.node_id(),
             Expression::Identifier(identifier) => identifier.node_id(),
             Expression::Integer(integer_literal) => integer_literal.node_id(),
             Expression::Double(double_literal) => double_literal.node_id(),
@@ -36,6 +39,7 @@ impl Expression {
             Expression::Binary(binary_expression) => binary_expression.source_range(),
             Expression::Negative(negative_expression) => negative_expression.source_range(),
             Expression::Call(call) => call.source_range(),
+            Expression::Path(path) => path.source_range(),
             Expression::Identifier(identifier) => identifier.source_range(),
             Expression::Integer(integer_literal) => integer_literal.source_range(),
             Expression::Double(double_literal) => double_literal.source_range(),

dmc-lib/src/ast/mod.rs

@@ -16,6 +16,7 @@ pub mod integer_literal;
 pub mod let_statement;
 pub mod negative_expression;
 pub mod parameter;
+pub mod path;
 pub mod statement;
 pub mod string_literal;
 pub mod type_use;

dmc-lib/src/ast/path.rs

@@ -0,0 +1,43 @@
+use crate::ast::NodeId;
+use crate::ast::expression::Expression;
+use crate::ast::identifier::Identifier;
+use crate::source_range::SourceRange;
+
+pub struct Path {
+    node_id: NodeId,
+    source_range: SourceRange,
+    base: Box<Expression>,
+    identifier: Box<Identifier>,
+}
+
+impl Path {
+    pub fn new(
+        node_id: NodeId,
+        source_range: SourceRange,
+        base: Expression,
+        identifier: Identifier,
+    ) -> Self {
+        Self {
+            node_id,
+            source_range,
+            base: base.into(),
+            identifier: identifier.into(),
+        }
+    }
+
+    pub fn node_id(&self) -> NodeId {
+        self.node_id
+    }
+
+    pub fn source_range(&self) -> &SourceRange {
+        &self.source_range
+    }
+
+    pub fn base(&self) -> &Expression {
+        &self.base
+    }
+
+    pub fn identifier(&self) -> &Identifier {
+        &self.identifier
+    }
+}

dmc-lib/src/intrinsics.rs

@@ -0,0 +1,51 @@
+use crate::semantic_analysis::analysis_context::AnalysisContext;
+use crate::semantic_analysis::scope::ScopeId;
+use crate::semantic_analysis::symbol::{ClassSymbol, FunctionSymbol, Symbol};
+use crate::semantic_analysis::type_info::{FunctionTypeInfo, InstanceTypeInfo, TypeInfo};
+use std::collections::HashMap;
+
+pub fn add_primitive_symbols_and_type_infos(ctx: &mut AnalysisContext, global_scope_id: ScopeId) {
+    let string_len_symbol = Symbol::Function(FunctionSymbol::new(
+        "len".into(),
+        None,
+        "core::String::len".into(),
+        true,
+        true,
+    ));
+    let string_len_symbol_id = ctx
+        .try_insert_symbol_in_scope(string_len_symbol, global_scope_id)
+        .unwrap();
+
+    let mut string_class_methods = HashMap::new();
+    string_class_methods.insert("len".into(), string_len_symbol_id);
+
+    let string_class_symbol = Symbol::Class(ClassSymbol::new(
+        "String".into(),
+        None,
+        "core::String".into(),
+        true,
+        HashMap::new(),
+        string_class_methods,
+    ));
+    let string_class_symbol_id = ctx
+        .try_insert_symbol_in_scope(string_class_symbol, global_scope_id)
+        .unwrap();
+
+    let string_instance_type_info_id = ctx.insert_type_info(TypeInfo::Instance(
+        InstanceTypeInfo::new(string_class_symbol_id),
+    ));
+
+    ctx.associate_symbol_to_type(string_class_symbol_id, string_instance_type_info_id);
+
+    let string_len_return_type_info_id = ctx.insert_type_info(TypeInfo::Int);
+
+    let string_len_type_info = TypeInfo::Function(FunctionTypeInfo::new(
+        vec![],
+        string_len_return_type_info_id,
+        Some(string_instance_type_info_id),
+    ));
+
+    let string_len_type_info_id = ctx.insert_type_info(string_len_type_info);
+
+    ctx.associate_symbol_to_type(string_len_symbol_id, string_len_type_info_id);
+}

dmc-lib/src/lib.rs

@@ -20,6 +20,7 @@ pub mod constants_table;
 pub mod diagnostic;
 mod diagnostic_factories;
 mod error_codes;
+pub mod intrinsics;
 pub mod ir;
 pub mod lexer;
 pub mod lowering;
@@ -104,7 +105,10 @@ impl SyntheticFunctionSession {
             Statement::Let(let_statement) => {
                 let ir_variable_info = IrVariableInfo::new(
                     let_statement.declared_name_owned(),
-                    to_ir_type_info(self.ctx.get_type_info_for_node(let_statement.node_id())),
+                    to_ir_type_info(
+                        &self.ctx,
+                        self.ctx.get_type_info_for_node(let_statement.node_id()),
+                    ),
                 );
                 let ir_stack_frame_variable_id = self
                     .env

dmc-lib/src/lowering/mod.rs

@@ -70,7 +70,7 @@ pub fn lower_to_ir_synthetic_function(
             let type_info_id =
                 session.ctx.nodes_to_type_infos()[&expression_statement.expression().node_id()];
             let type_info = &session.ctx.type_infos()[type_info_id];
-            return_type_info_to_ir_type_info(type_info)
+            return_type_info_to_ir_type_info(session.ctx(), type_info)
         }
     };
 
@@ -275,7 +275,7 @@ fn lower_to_ir_function(function: &Function, ctx: &AnalysisContext) -> IrFunctio
         storage_env.take_parameters(),
         storage_env.ir_stack_frame_variables.clone(),
         storage_env.ir_free_variables.clone(),
-        return_type_info_to_ir_type_info(return_type_info),
+        return_type_info_to_ir_type_info(ctx, return_type_info),
         blocks,
     )
 }
@@ -290,7 +290,7 @@ fn lower_to_ir_parameters(
         let parameter_type_info = &ctx.type_infos()[parameter_type_info_id];
         fn_ctx.storage_env_mut().new_parameter_for(
             parameter.declared_name(),
-            to_ir_type_info(parameter_type_info),
+            to_ir_type_info(ctx, parameter_type_info),
             ctx.nodes_to_symbols()[&parameter.node_id()],
         );
     }
@@ -349,7 +349,7 @@ fn lower_to_ir_let_statement(
         .unwrap_or_else(|| {
             fn_ctx.storage_env_mut().new_free_variable_for(
                 let_statement.declared_name(),
-                to_ir_type_info(type_info),
+                to_ir_type_info(ctx, type_info),
                 symbol_id,
             )
         });
@@ -384,7 +384,7 @@ fn lower_to_ir_expression_statement(
         let result_type_info = &ctx.type_infos()[result_type_info_id];
         let t_var_ir_variable_id = fn_ctx
             .storage_env_mut()
-            .new_t_var(to_ir_type_info(result_type_info));
+            .new_t_var(to_ir_type_info(ctx, result_type_info));
 
         let ir_statement = IrStatement::Assign(IrAssign::new(t_var_ir_variable_id, ir_operation));
         fn_ctx.current_block_statements.push(ir_statement);
@@ -439,6 +439,9 @@ fn lower_expression_to_ir_operation(
             ))
         }
         Expression::Call(call) => IrOperation::Call(lower_to_ir_call(call, ctx, fn_ctx)),
+        Expression::Path(_path) => {
+            todo!()
+        }
         Expression::Identifier(identifier) => {
             let identifier_symbol_id = ctx.nodes_to_symbols()[&identifier.node_id()];
             let identifier_ir_variable =
@@ -479,7 +482,7 @@ fn lower_expression_to_ir_expression(
             let result_type_info = &ctx.type_infos()[result_type_info_id];
             let destination_ir_variable = fn_ctx
                 .storage_env_mut()
-                .new_t_var(to_ir_type_info(result_type_info));
+                .new_t_var(to_ir_type_info(ctx, result_type_info));
 
             // make assign statement to destination temp var
             let ir_assign = IrAssign::new(destination_ir_variable.clone(), ir_operation);
@@ -503,7 +506,7 @@ fn lower_expression_to_ir_expression(
             let result_type_info = &ctx.type_infos()[result_type_info_id];
             let destination_ir_variable = fn_ctx
                 .storage_env_mut()
-                .new_t_var(to_ir_type_info(result_type_info));
+                .new_t_var(to_ir_type_info(ctx, result_type_info));
             let ir_assign = IrAssign::new(destination_ir_variable.clone(), ir_operation);
 
             // push the statement which does the multiply by negative one
@@ -521,7 +524,7 @@ fn lower_expression_to_ir_expression(
             let return_type_info = &ctx.type_infos()[return_type_info_id];
             let t_var_ir_variable = fn_ctx
                 .storage_env_mut()
-                .new_t_var(to_ir_type_info(return_type_info));
+                .new_t_var(to_ir_type_info(ctx, return_type_info));
 
             // assign call to temp var, return temp var expression
             let ir_operation = IrOperation::Call(ir_call);
@@ -533,6 +536,9 @@ fn lower_expression_to_ir_expression(
             // return an expression referencing the temp var
             IrExpression::Variable(t_var_ir_variable)
         }
+        Expression::Path(_path) => {
+            todo!()
+        }
         Expression::Identifier(identifier) => {
             let rhs_symbol_id = ctx.nodes_to_symbols()[&identifier.node_id()];
             if let Some(rhs_ir_variable) =
@@ -565,11 +571,29 @@ fn lower_to_ir_call(
     let callee_symbol = &ctx.symbols()[callee_symbol_id];
     match callee_symbol {
         Symbol::Function(function_symbol) => {
-            let arguments = call
-                .arguments()
-                .iter()
-                .map(|e| lower_expression_to_ir_expression(e, ctx, fn_ctx))
-                .collect();
+            let mut arguments = Vec::new();
+            if function_symbol.is_method() {
+                let this = match call.callee() {
+                    Expression::Path(path) => {
+                        lower_expression_to_ir_expression(path.base(), ctx, fn_ctx)
+                    }
+                    Expression::Identifier(identifier) => {
+                        // A self object, like:
+                        // class Foo
+                        //   fn bar() "hello" end
+                        //   fn greet() bar() end
+                        // end
+                        todo!()
+                    }
+                    _ => panic!(
+                        "Cannot determine method's this expression when not Path or Identifier"
+                    ),
+                };
+                arguments.push(this);
+            }
+            for expression in call.arguments() {
+                arguments.push(lower_expression_to_ir_expression(expression, ctx, fn_ctx));
+            }
             IrCall::new(
                 function_symbol.fqn_owned(),
                 arguments,

dmc-lib/src/lowering/util.rs

@@ -1,24 +1,35 @@
 use crate::ir::ir_type_info::IrTypeInfo;
+use crate::semantic_analysis::analysis_context::AnalysisContext;
 use crate::semantic_analysis::type_info::TypeInfo;
 
-pub fn to_ir_type_info(sa_type_info: &TypeInfo) -> IrTypeInfo {
+pub fn to_ir_type_info(ctx: &AnalysisContext, sa_type_info: &TypeInfo) -> IrTypeInfo {
     match sa_type_info {
-        TypeInfo::String => IrTypeInfo::String,
+        TypeInfo::Instance(instance_type_info) => {
+            let symbol = &ctx.symbols()[instance_type_info.class_symbol_id()];
+            if symbol.unwrap_class_symbol().fqn() == "core::String" {
+                IrTypeInfo::String
+            } else {
+                todo!("Non-string Instance types")
+            }
+        }
         TypeInfo::Int => IrTypeInfo::Int,
         TypeInfo::Double => IrTypeInfo::Double,
         TypeInfo::Void => IrTypeInfo::Void,
         _ => {
-            panic!("BUG! Unknown sa_type_info: {}", sa_type_info);
+            panic!("BUG! Unknown sa_type_info: {:?}", sa_type_info);
         }
     }
 }
 
-pub fn return_type_info_to_ir_type_info(return_type_info: &TypeInfo) -> Option<IrTypeInfo> {
+pub fn return_type_info_to_ir_type_info(
+    ctx: &AnalysisContext,
+    return_type_info: &TypeInfo,
+) -> Option<IrTypeInfo> {
     match return_type_info {
-        TypeInfo::String | TypeInfo::Int | TypeInfo::Double => {
-            Some(to_ir_type_info(return_type_info))
+        TypeInfo::Instance(_) | TypeInfo::Int | TypeInfo::Double => {
+            Some(to_ir_type_info(ctx, return_type_info))
         }
         TypeInfo::Void => None,
-        _ => panic!(),
+        _ => panic!("BUG! Unknown return_type_info: {:?}", return_type_info),
     }
 }

dmc-lib/src/parser.rs

@@ -18,6 +18,7 @@ use crate::ast::integer_literal::IntegerLiteral;
 use crate::ast::let_statement::LetStatement;
 use crate::ast::negative_expression::NegativeExpression;
 use crate::ast::parameter::Parameter;
+use crate::ast::path::Path;
 use crate::ast::statement::Statement;
 use crate::ast::string_literal::StringLiteral;
 use crate::ast::type_use::TypeUse;
@@ -166,21 +167,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn advance_until(&mut self, token_kinds: &[TokenKind]) {
-        while self.current.is_some() {
-            match &self.current {
-                None => {
-                    // reached eoi
-                }
-                Some(current) => {
-                    if token_kinds.contains(&current.kind()) {
-                        break;
-                    }
-                }
-            }
-        }
-    }
-
     fn advance(&mut self) {
         fn fetch(lexer: &mut Lexer, diagnostics: &mut Diagnostics) -> Option<Token> {
             let mut maybe_token: Option<Token> = None;
@@ -1038,6 +1024,21 @@ impl<'a> Parser<'a> {
                     TokenKind::LeftParentheses => {
                         expression = Expression::Call(self.call(expression));
                     }
+                    TokenKind::Dot => {
+                        self.advance(); // .
+                        if let Some(identifier) = self.identifier() {
+                            let source_range = SourceRange::new(
+                                expression.source_range().start(),
+                                identifier.source_range().end(),
+                            );
+                            expression = Expression::Path(Path::new(
+                                self.next_node_id(),
+                                source_range,
+                                expression,
+                                identifier,
+                            ));
+                        }
+                    }
                     _ => break,
                 }
             }
@@ -1047,6 +1048,18 @@ impl<'a> Parser<'a> {
         }
     }
 
+    fn identifier(&mut self) -> Option<Identifier> {
+        if let Some(identifier_token) = self.expect_advance(TokenKind::Identifier) {
+            Some(Identifier::new(
+                self.next_node_id(),
+                self.token_text(&identifier_token),
+                SourceRange::new(identifier_token.start(), identifier_token.end()),
+            ))
+        } else {
+            None
+        }
+    }
+
     fn expression_base(&mut self) -> Option<Expression> {
         let current = match self.current.as_ref() {
             Some(current) => current,
@@ -1350,6 +1363,21 @@ mod smoke_tests {
     fn class_with_generic_param() {
         smoke_test("class Foo<T> end");
     }
+
+    #[test]
+    fn single_member_access() {
+        smoke_test("fn main(foo: Foo) foo.bar end")
+    }
+
+    #[test]
+    fn double_member_access() {
+        smoke_test("fn main(foo: Foo) foo.bar.baz end")
+    }
+
+    #[test]
+    fn call_member() {
+        smoke_test("fn main(s: String) s.len() end")
+    }
 }
 
 #[cfg(test)]

dmc-lib/src/semantic_analysis/analysis_context/helpers.rs

@@ -0,0 +1,21 @@
+use crate::semantic_analysis::analysis_context::AnalysisContext;
+use crate::semantic_analysis::type_info::TypeInfo;
+
+pub fn get_name_for_type<'ctx>(type_info: &TypeInfo, ctx: &'ctx AnalysisContext) -> &'ctx str {
+    match type_info {
+        TypeInfo::Any => "Any",
+        TypeInfo::Function(_function_type_info) => {
+            todo!()
+        }
+        TypeInfo::Instance(instance_type_info) => {
+            let class_symbol_id = instance_type_info.class_symbol_id();
+            let class_symbol = &ctx.symbols()[class_symbol_id];
+            class_symbol.declared_name()
+        }
+        TypeInfo::String => "String",
+        TypeInfo::Int => "Int",
+        TypeInfo::Double => "Double",
+        TypeInfo::Void => "Void",
+        TypeInfo::__Error => panic!("TypeInfo::__Error should never be shown to the user."),
+    }
+}

dmc-lib/src/semantic_analysis/analysis_context/mod.rs

@@ -1,3 +1,5 @@
+pub mod helpers;
+
 use crate::ast::NodeId;
 use crate::diagnostic::Diagnostic;
 use crate::diagnostic_factories::symbol_not_found;
@@ -44,14 +46,6 @@ impl AnalysisContext {
         todo!()
     }
 
-    pub fn scopes(&self) -> &[Scope] {
-        &self.scopes
-    }
-
-    pub fn scopes_mut(&mut self) -> &mut Vec<Scope> {
-        &mut self.scopes
-    }
-
     pub fn symbols(&self) -> &[Symbol] {
         &self.symbols
     }
@@ -86,10 +80,11 @@ impl AnalysisContext {
         fqn.join("::")
     }
 
-    pub fn push_scope(&mut self, _debug_name: &str) {
+    pub fn push_scope(&mut self, _debug_name: &str) -> ScopeId {
         let scope = Scope::new(self.current_scope_id);
         self.scopes.push(scope);
         self.current_scope_id = Some(self.scopes.len() - 1);
+        self.current_scope_id.unwrap()
     }
 
     fn get_scope(&self, scope_id: ScopeId) -> &Scope {
@@ -125,6 +120,11 @@ impl AnalysisContext {
         );
     }
 
+    /// Inserts the given symbol into the Scope corresponding to the given ScopeId. **This is a low
+    /// level operation and alternate methods should be preferred.**
+    ///
+    /// Danger: If a symbol already exists in the corresponding Scope with the same declared name,
+    /// it will be overwritten, leading to dangling symbols/symbol ids.
     fn insert_symbol_in_scope(&mut self, scope_id: ScopeId, symbol: Symbol) -> SymbolId {
         // get declared name
         let declared_name = symbol.declared_name_owned();
@@ -159,14 +159,14 @@ impl AnalysisContext {
         &mut self,
         to_insert: Symbol,
         scope_id: ScopeId,
-    ) -> Result<(), Diagnostic> {
+    ) -> Result<SymbolId, Diagnostic> {
         let scope = self.get_scope(scope_id);
         if let Some(already_declared) = self.get_symbol_in_scope(scope, to_insert.declared_name()) {
             Err(symbol_already_declared(already_declared, &to_insert))
         } else {
-            self.insert_symbol_in_scope(scope_id, to_insert);
+            let symbol_id = self.insert_symbol_in_scope(scope_id, to_insert);
             // no associated node, so no need to update self.nodes_to_symbols
-            Ok(())
+            Ok(symbol_id)
         }
     }
 
@@ -261,12 +261,16 @@ impl AnalysisContext {
             .insert(node_id, self.type_infos.len() - 1);
     }
 
+    pub fn associate_symbol_to_type(&mut self, symbol_id: SymbolId, type_info_id: TypeInfoId) {
+        self.symbols_to_type_infos.insert(symbol_id, type_info_id);
+    }
+
     pub fn associate_node_and_symbol_to_type(&mut self, node_id: NodeId, type_info_id: TypeInfoId) {
         let symbol_id = self
             .nodes_to_symbols
             .get(&node_id)
             .expect(&format!("node_id {} has no associated symbol", node_id));
-        self.symbols_to_type_infos.insert(*symbol_id, type_info_id);
+        self.associate_symbol_to_type(*symbol_id, type_info_id);
         self.nodes_to_type_infos.insert(node_id, type_info_id);
     }
 
@@ -305,4 +309,25 @@ impl AnalysisContext {
         ));
         *symbol_type_info_id
     }
+
+    pub fn find_symbol_by_fqn(&self, fqn: &str) -> Option<SymbolId> {
+        // This is quite naive and probably very slow; we will certainly use trees of HashMaps (or
+        // structs with a HashMap and children) to represent the fqn hierarchy.
+        for (id, symbol) in self.symbols.iter().enumerate() {
+            match symbol {
+                Symbol::Class(class_symbol) => {
+                    if class_symbol.fqn() == fqn {
+                        return Some(id);
+                    }
+                }
+                Symbol::Function(function_symbol) => {
+                    if function_symbol.fqn() == fqn {
+                        return Some(id);
+                    }
+                }
+                _ => {}
+            }
+        }
+        None
+    }
 }

dmc-lib/src/semantic_analysis/collect_scopes.rs

@@ -9,11 +9,10 @@ use crate::ast::function::Function;
 use crate::ast::identifier::Identifier;
 use crate::ast::let_statement::LetStatement;
 use crate::ast::negative_expression::NegativeExpression;
+use crate::ast::path::Path;
 use crate::ast::statement::Statement;
 use crate::semantic_analysis::analysis_context::AnalysisContext;
 
-/// N.b.: the parent_scope_id refers to the **parent** of the compilation unit scope, and must
-/// be a valid (non-panicking) index of `scopes`.
 pub fn collect_scopes_compilation_unit(
     compilation_unit: &CompilationUnit,
     ctx: &mut AnalysisContext,
@@ -112,6 +111,9 @@ fn collect_scopes_expression(expression: &Expression, ctx: &mut AnalysisContext)
         Expression::Call(call) => {
             collect_scopes_call(call, ctx);
         }
+        Expression::Path(path) => {
+            collect_scopes_path(path, ctx);
+        }
         Expression::Identifier(identifier) => {
             collect_scopes_identifier(identifier, ctx);
         }
@@ -143,6 +145,11 @@ fn collect_scopes_call(call: &Call, ctx: &mut AnalysisContext) {
     collect_scopes_expression(call.callee(), ctx);
 }
 
+fn collect_scopes_path(path: &Path, ctx: &mut AnalysisContext) {
+    collect_scopes_expression(path.base(), ctx);
+    // do not need to collect a scope for the identifier, since that is looked up via the base
+}
+
 fn collect_scopes_identifier(identifier: &Identifier, ctx: &mut AnalysisContext) {
     ctx.associate_node_to_current_scope(identifier.node_id());
 }

dmc-lib/src/semantic_analysis/collect_symbols.rs

@@ -38,6 +38,7 @@ fn collect_symbols_function(
         Some(function.declared_name_source_range()),
         fqn,
         false,
+        false,
     ));
 
     // insert
@@ -70,6 +71,7 @@ fn collect_symbols_extern_function(
         Some(extern_function.declared_name_source_range()),
         fqn,
         true,
+        false,
     ));
 
     // insert function symbol

dmc-lib/src/semantic_analysis/collect_types.rs

@@ -21,23 +21,30 @@ fn collect_types_function(function: &Function, ctx: &mut AnalysisContext) {
 
     let return_type_info = match function.return_type() {
         None => TypeInfo::Void,
-        Some(type_use) => declared_name_to_type_info(type_use.declared_name()),
+        Some(type_use) => declared_name_to_type_info(ctx, type_use.declared_name()),
     };
     let return_type_info_id = ctx.insert_type_info(return_type_info);
 
     let function_type_info = TypeInfo::Function(FunctionTypeInfo::new(
         parameter_type_info_ids,
         return_type_info_id,
+        None,
     ));
     let function_type_info_id = ctx.insert_type_info(function_type_info);
 
     ctx.associate_node_and_symbol_to_type(function.node_id(), function_type_info_id);
 }
 
-fn declared_name_to_type_info(declared_name: &str) -> TypeInfo {
+fn declared_name_to_type_info(ctx: &AnalysisContext, declared_name: &str) -> TypeInfo {
     match declared_name {
         "Any" => TypeInfo::Any,
-        "String" => TypeInfo::String,
+        "String" => {
+            // todo: resolve this like a normal instance type
+            let symbol_id = ctx
+                .find_symbol_by_fqn("core::String")
+                .expect("Missing core::String from ctx");
+            ctx.type_infos()[symbol_id].clone()
+        }
         "Int" => TypeInfo::Int,
         "Double" => TypeInfo::Double,
         "Void" => TypeInfo::Void,
@@ -51,7 +58,7 @@ fn collect_and_get_parameter_type_info_ids(
 ) -> Vec<TypeInfoId> {
     let mut parameter_type_info_ids: Vec<TypeInfoId> = Vec::new();
     for parameter in parameters {
-        let type_info = declared_name_to_type_info(parameter.type_use().declared_name());
+        let type_info = declared_name_to_type_info(ctx, parameter.type_use().declared_name());
         let type_info_id = ctx.insert_type_info(type_info);
         parameter_type_info_ids.push(type_info_id);
 
@@ -66,12 +73,13 @@ fn collect_types_extern_function(extern_function: &ExternFunction, ctx: &mut Ana
         collect_and_get_parameter_type_info_ids(extern_function.parameters(), ctx);
 
     let return_type_info =
-        declared_name_to_type_info(extern_function.return_type().declared_name());
+        declared_name_to_type_info(ctx, extern_function.return_type().declared_name());
     let return_type_info_id = ctx.insert_type_info(return_type_info);
 
     let function_type_info = TypeInfo::Function(FunctionTypeInfo::new(
         parameter_type_info_ids,
         return_type_info_id,
+        None,
     ));
 
     let function_type_info_id = ctx.insert_type_info(function_type_info);

dmc-lib/src/semantic_analysis/resolve_names.rs

@@ -10,6 +10,7 @@ use crate::ast::identifier::Identifier;
 use crate::ast::let_statement::LetStatement;
 use crate::ast::negative_expression::NegativeExpression;
 use crate::ast::parameter::Parameter;
+use crate::ast::path::Path;
 use crate::ast::statement::Statement;
 use crate::diagnostic::Diagnostics;
 use crate::semantic_analysis::analysis_context::AnalysisContext;
@@ -195,6 +196,9 @@ fn resolve_names_expression(
         Expression::Call(call) => {
             resolve_names_call(call, ctx, diagnostics, phase);
         }
+        Expression::Path(path) => {
+            resolve_names_path(path, ctx, diagnostics, phase);
+        }
         Expression::Identifier(identifier) => {
             resolve_names_identifier(identifier, ctx, diagnostics, phase);
         }
@@ -235,6 +239,18 @@ fn resolve_names_call(
     resolve_names_expression(call.callee(), ctx, diagnostics, phase);
 }
 
+fn resolve_names_path(
+    path: &Path,
+    ctx: &mut AnalysisContext,
+    diagnostics: &mut Diagnostics,
+    phase: ExpressionResolutionPhase,
+) {
+    // resolve base (left part)
+    resolve_names_expression(path.base(), ctx, diagnostics, phase);
+    // We cannot yet determine if the path's identifier (right part) is a valid memeber of the left,
+    // since we don't have type information yet. Therefore, it is deferred until type-checking.
+}
+
 fn resolve_names_identifier(
     identifier: &Identifier,
     ctx: &mut AnalysisContext,

dmc-lib/src/semantic_analysis/resolve_types/mod.rs

@@ -10,14 +10,16 @@ use crate::ast::identifier::Identifier;
 use crate::ast::let_statement::LetStatement;
 use crate::ast::negative_expression::NegativeExpression;
 use crate::ast::parameter::Parameter;
+use crate::ast::path::Path;
 use crate::ast::statement::Statement;
 use crate::diagnostic::{Diagnostic, Diagnostics};
 use crate::error_codes::BINARY_INCOMPATIBLE_TYPES;
 use crate::semantic_analysis::analysis_context::AnalysisContext;
+use crate::semantic_analysis::analysis_context::helpers::get_name_for_type;
 use crate::semantic_analysis::resolve_types::type_analysis::{
     are_binary_op_compatible, binary_op_result, can_assign_right_to_left, can_negate, negate_result,
 };
-use crate::semantic_analysis::type_info::TypeInfo;
+use crate::semantic_analysis::type_info::{InstanceTypeInfo, TypeInfo};
 
 pub struct ResolveTypesResult(pub Diagnostics);
 
@@ -109,10 +111,12 @@ fn resolve_types_assign_statement(
     let destination_type_info =
         ctx.get_type_info_for_node(assign_statement.destination().node_id());
 
-    if !can_assign_right_to_left(destination_type_info, value_type_info) {
+    if !can_assign_right_to_left(destination_type_info, value_type_info, ctx) {
+        let destination_type_name = get_name_for_type(destination_type_info, ctx);
+        let value_type_name = get_name_for_type(value_type_info, ctx);
         let message = format!(
             "Incompatible types: cannot assign {} from {}",
-            destination_type_info, value_type_info
+            destination_type_name, value_type_name
         );
         let diagnostic = Diagnostic::new(
             &message,
@@ -138,6 +142,9 @@ fn resolve_types_expression(
         Expression::Call(call) => {
             resolve_types_call(call, ctx, diagnostics);
         }
+        Expression::Path(path) => {
+            resolve_types_path(path, ctx, diagnostics);
+        }
         Expression::Identifier(identifier) => {
             resolve_types_identifier(identifier, ctx);
         }
@@ -148,7 +155,13 @@ fn resolve_types_expression(
             ctx.insert_type_info_for_node(TypeInfo::Double, double_literal.node_id());
         }
         Expression::String(string_literal) => {
-            ctx.insert_type_info_for_node(TypeInfo::String, string_literal.node_id());
+            let string_class_symbol_id = ctx
+                .find_symbol_by_fqn("core::String")
+                .expect("core::String is missing from ctx.");
+            ctx.insert_type_info_for_node(
+                TypeInfo::Instance(InstanceTypeInfo::new(string_class_symbol_id)),
+                string_literal.node_id(),
+            );
         }
     }
 }
@@ -164,9 +177,9 @@ fn resolve_types_binary_expression(
     let lhs_type_info = ctx.get_type_info_for_node(binary_expression.lhs().node_id());
     let rhs_type_info = ctx.get_type_info_for_node(binary_expression.rhs().node_id());
 
-    if are_binary_op_compatible(binary_expression.op(), lhs_type_info, rhs_type_info) {
+    if are_binary_op_compatible(ctx, binary_expression.op(), lhs_type_info, rhs_type_info) {
         let result_type_info =
-            binary_op_result(binary_expression.op(), lhs_type_info, rhs_type_info);
+            binary_op_result(ctx, binary_expression.op(), lhs_type_info, rhs_type_info);
         ctx.insert_type_info_for_node(result_type_info, binary_expression.node_id());
     } else {
         let op_name = match binary_expression.op() {
@@ -181,9 +194,11 @@ fn resolve_types_binary_expression(
             BinaryOperation::BitwiseXor => "bitwise xor",
             BinaryOperation::BitwiseOr => "bitwise or",
         };
+        let lhs_type_name = get_name_for_type(lhs_type_info, ctx);
+        let rhs_type_name = get_name_for_type(rhs_type_info, ctx);
         let message = format!(
             "Incompatible types: cannot {} {} and {}",
-            op_name, lhs_type_info, rhs_type_info
+            op_name, lhs_type_name, rhs_type_name
         );
         let diagnostic = Diagnostic::new(
             &message,
@@ -211,7 +226,8 @@ fn resolve_types_negative_expression(
         let result_type_info = negate_result(operand_type_info);
         ctx.insert_type_info_for_node(result_type_info, negative_expression.node_id());
     } else {
-        let message = format!("Incompatible type: cannot negate {}", operand_type_info);
+        let operand_type_name = get_name_for_type(operand_type_info, ctx);
+        let message = format!("Incompatible type: cannot negate {}", operand_type_name);
         let diagnostic = Diagnostic::new(
             &message,
             negative_expression.source_range().start(),
@@ -255,25 +271,26 @@ fn resolve_types_call(call: &Call, ctx: &mut AnalysisContext, diagnostics: &mut
                 // of the function
             }
 
-            // check argument types
+            // check argument types, but only if we have the right number of arguments
             let parameter_type_ids = function_type_info.parameter_type_ids();
-            for i in 0..parameter_type_ids.len() {
-                let argument_type_info = ctx.get_type_info_for_node(arguments[i].node_id());
-                let parameter_type_info = ctx.get_type_info_by_id(parameter_type_ids[i]); // n.b. different method
-                if !can_assign_right_to_left(parameter_type_info, argument_type_info) {
-                    let message = format!(
-                        "Incompatible types: cannot assign {} to {}",
-                        argument_type_info, parameter_type_info
-                    );
-                    let diagnostic = Diagnostic::new(
-                        &message,
-                        arguments[i].source_range().start(),
-                        arguments[i].source_range().end(),
-                    );
-                    diagnostics.push(diagnostic);
-
-                    // do not push an error type because the result of the whole call is the return type
-                    // of the function
+            if arguments.len() == parameter_type_ids.len() {
+                for i in 0..parameter_type_ids.len() {
+                    let argument_type_info = ctx.get_type_info_for_node(arguments[i].node_id());
+                    let parameter_type_info = ctx.get_type_info_by_id(parameter_type_ids[i]); // n.b. different method
+                    if !can_assign_right_to_left(parameter_type_info, argument_type_info, ctx) {
+                        let parameter_type_name = get_name_for_type(parameter_type_info, ctx);
+                        let argument_type_name = get_name_for_type(argument_type_info, ctx);
+                        let message = format!(
+                            "Incompatible types: cannot assign {} to {}",
+                            argument_type_name, parameter_type_name
+                        );
+                        let diagnostic = Diagnostic::new(
+                            &message,
+                            arguments[i].source_range().start(),
+                            arguments[i].source_range().end(),
+                        );
+                        diagnostics.push(diagnostic);
+                    }
                 }
             }
 
@@ -286,7 +303,8 @@ fn resolve_types_call(call: &Call, ctx: &mut AnalysisContext, diagnostics: &mut
             ctx.insert_type_info_for_node(TypeInfo::__Error, call.node_id());
         }
         _ => {
-            let message = format!("Incompatible type: cannot call type {}", callee_type_info);
+            let callee_type_name = get_name_for_type(callee_type_info, ctx);
+            let message = format!("Incompatible type: cannot call type {}", callee_type_name);
             let diagnostic = Diagnostic::new(
                 &message,
                 call.callee().source_range().start(),
@@ -300,6 +318,73 @@ fn resolve_types_call(call: &Call, ctx: &mut AnalysisContext, diagnostics: &mut
     }
 }
 
+fn resolve_types_path(path: &Path, ctx: &mut AnalysisContext, diagnostics: &mut Diagnostics) {
+    resolve_types_expression(path.base(), ctx, diagnostics);
+    let base_type_info = ctx.get_type_info_for_node(path.base().node_id());
+    match base_type_info {
+        TypeInfo::Instance(instance_type_info) => {
+            let class_symbol_id = instance_type_info.class_symbol_id();
+            let class_symbol = ctx.symbols()[class_symbol_id].unwrap_class_symbol();
+            // try methods and then fields
+            let maybe_symbol_id = class_symbol
+                .field_symbol_ids()
+                .get(path.identifier().name())
+                .or_else(|| {
+                    class_symbol
+                        .method_symbol_ids()
+                        .get(path.identifier().name())
+                });
+            match maybe_symbol_id {
+                Some(member_symbol_id) => {
+                    // here, we can perform logic such as visibility checking
+                    // for now, we set the node's symbol and type to the appropriate values
+                    let type_info_id = ctx.symbols_to_type_infos()[member_symbol_id];
+                    let type_info = ctx.get_type_info_by_id(type_info_id).clone();
+                    ctx.associate_node_to_symbol(path.node_id(), *member_symbol_id);
+                    ctx.insert_type_info_for_node(type_info, path.node_id());
+                }
+                None => {
+                    let base_type_name = get_name_for_type(base_type_info, ctx);
+                    let message = format!(
+                        "Type {} has no such member: {}",
+                        base_type_name,
+                        path.identifier().name()
+                    );
+                    let diagnostic = Diagnostic::new(
+                        &message,
+                        path.identifier().source_range().start(),
+                        path.identifier().source_range().end(),
+                    );
+                    diagnostics.push(diagnostic);
+
+                    // bubble it up:
+                    ctx.insert_type_info_for_node(TypeInfo::__Error, path.node_id());
+                }
+            }
+        }
+        TypeInfo::__Error => {
+            // bubble it up
+            ctx.insert_type_info_for_node(TypeInfo::__Error, path.node_id());
+        }
+        _ => {
+            let base_type_name = get_name_for_type(base_type_info, ctx);
+            let message = format!(
+                "Impossible operation: type {} does not have members to access",
+                base_type_name
+            );
+            let diagnostic = Diagnostic::new(
+                &message,
+                path.source_range().start(),
+                path.source_range().end(),
+            );
+            diagnostics.push(diagnostic);
+
+            // bubble it up
+            ctx.insert_type_info_for_node(TypeInfo::__Error, path.node_id());
+        }
+    }
+}
+
 fn resolve_types_identifier(identifier: &Identifier, ctx: &mut AnalysisContext) {
     let type_info_id = ctx.lookup_type_for_node_via_symbol(identifier.node_id());
     ctx.associate_node_to_type(identifier.node_id(), type_info_id);

dmc-lib/src/semantic_analysis/resolve_types/type_analysis.rs

@@ -1,13 +1,19 @@
 use crate::ast::binary_expression::BinaryOperation;
+use crate::semantic_analysis::analysis_context::AnalysisContext;
 use crate::semantic_analysis::type_info::TypeInfo;
 
-pub fn are_binary_op_compatible(op: &BinaryOperation, left: &TypeInfo, right: &TypeInfo) -> bool {
+pub fn are_binary_op_compatible(
+    ctx: &AnalysisContext,
+    op: &BinaryOperation,
+    left: &TypeInfo,
+    right: &TypeInfo,
+) -> bool {
     match op {
         BinaryOperation::Multiply
         | BinaryOperation::Divide
         | BinaryOperation::Modulo
         | BinaryOperation::Subtract => are_numbers(left, right),
-        BinaryOperation::Add => are_numbers_or_strings(left, right),
+        BinaryOperation::Add => are_numbers_or_strings(ctx, left, right),
         BinaryOperation::LeftShift
         | BinaryOperation::RightShift
         | BinaryOperation::BitwiseAnd
@@ -24,21 +30,35 @@ fn are_numbers(t0: &TypeInfo, t1: &TypeInfo) -> bool {
     is_number(t0) && is_number(t1)
 }
 
-fn are_numbers_or_strings(t0: &TypeInfo, t1: &TypeInfo) -> bool {
-    (is_number(t0) || matches!(t0, TypeInfo::String))
-        && (is_number(t1) || matches!(t1, TypeInfo::String))
+fn are_numbers_or_strings(ctx: &AnalysisContext, t0: &TypeInfo, t1: &TypeInfo) -> bool {
+    (is_number(t0) || is_string(ctx, t0)) && (is_number(t1) || is_string(ctx, t1))
+}
+
+fn is_string(ctx: &AnalysisContext, type_info: &TypeInfo) -> bool {
+    match type_info {
+        TypeInfo::Instance(instance_type_info) => {
+            let class_symbol = &ctx.symbols()[instance_type_info.class_symbol_id()];
+            class_symbol.unwrap_class_symbol().fqn() == "core::String"
+        }
+        _ => false,
+    }
 }
 
 fn are_ints(t0: &TypeInfo, t1: &TypeInfo) -> bool {
     matches!(t0, TypeInfo::Int) && matches!(t1, TypeInfo::Int)
 }
 
-pub fn binary_op_result(op: &BinaryOperation, left: &TypeInfo, right: &TypeInfo) -> TypeInfo {
+pub fn binary_op_result(
+    ctx: &AnalysisContext,
+    op: &BinaryOperation,
+    left: &TypeInfo,
+    right: &TypeInfo,
+) -> TypeInfo {
     match op {
         BinaryOperation::Multiply => numbers_binary_result(left, right),
         BinaryOperation::Divide => TypeInfo::Double, // okay for now
         BinaryOperation::Modulo => numbers_binary_result(left, right), // same properties as multiplication
-        BinaryOperation::Add => add_result(left, right),
+        BinaryOperation::Add => add_result(ctx, left, right),
         BinaryOperation::Subtract => numbers_binary_result(left, right),
         BinaryOperation::LeftShift
         | BinaryOperation::RightShift
@@ -66,22 +86,40 @@ fn numbers_binary_result(left: &TypeInfo, right: &TypeInfo) -> TypeInfo {
     }
 }
 
-fn add_result(left: &TypeInfo, right: &TypeInfo) -> TypeInfo {
+fn add_result(ctx: &AnalysisContext, left: &TypeInfo, right: &TypeInfo) -> TypeInfo {
     match left {
+        TypeInfo::Instance(left_instance_type_info) => {
+            if is_string(ctx, left) {
+                TypeInfo::Instance(left_instance_type_info.clone())
+            } else {
+                todo!("Adding with non-String, non-number types")
+            }
+        }
         TypeInfo::Int => match right {
+            TypeInfo::Instance(right_instance_type_info) => {
+                if is_string(ctx, right) {
+                    TypeInfo::Instance(right_instance_type_info.clone())
+                } else {
+                    todo!("Adding with non-String, non-number types")
+                }
+            }
             TypeInfo::Int => TypeInfo::Int,
             TypeInfo::Double => TypeInfo::Double,
-            TypeInfo::String => TypeInfo::String,
             TypeInfo::__Error => TypeInfo::__Error,
             _ => panic!(),
         },
         TypeInfo::Double => match right {
+            TypeInfo::Instance(right_instance_type_info) => {
+                if is_string(ctx, right) {
+                    TypeInfo::Instance(right_instance_type_info.clone())
+                } else {
+                    todo!("Adding with non-String, non-number types")
+                }
+            }
             TypeInfo::Int | TypeInfo::Double => TypeInfo::Double,
-            TypeInfo::String => TypeInfo::String,
             TypeInfo::__Error => TypeInfo::__Error,
             _ => panic!(),
         },
-        TypeInfo::String => TypeInfo::String,
         TypeInfo::__Error => TypeInfo::__Error,
         _ => panic!(),
     }
@@ -103,12 +141,18 @@ pub fn negate_result(operand: &TypeInfo) -> TypeInfo {
     }
 }
 
-pub fn can_assign_right_to_left(left: &TypeInfo, right: &TypeInfo) -> bool {
+pub fn can_assign_right_to_left(left: &TypeInfo, right: &TypeInfo, ctx: &AnalysisContext) -> bool {
     match left {
         TypeInfo::Any => true,
         TypeInfo::Function(_) => {
             panic!()
         }
+        TypeInfo::Instance(left_instance_type_info) => match right {
+            TypeInfo::Instance(right_instance_type_info) => {
+                left_instance_type_info.can_assign_from(right_instance_type_info, ctx)
+            }
+            _ => false,
+        },
         TypeInfo::String => match right {
             TypeInfo::String => true,
             _ => false,

dmc-lib/src/semantic_analysis/symbol.rs

@@ -1,10 +1,14 @@
+use crate::semantic_analysis::analysis_context::AnalysisContext;
 use crate::source_range::SourceRange;
+use std::collections::HashMap;
 use std::rc::Rc;
 
 pub type SymbolId = usize;
 
 #[derive(Debug)]
 pub enum Symbol {
+    Class(ClassSymbol),
+    Field(FieldSymbol),
     Function(FunctionSymbol),
     Parameter(ParameterSymbol),
     Variable(VariableSymbol),
@@ -13,6 +17,8 @@ pub enum Symbol {
 impl Symbol {
     pub fn declared_name(&self) -> &str {
         match self {
+            Symbol::Class(class_symbol) => class_symbol.declared_name(),
+            Symbol::Field(field_symbol) => &field_symbol.declared_name(),
             Symbol::Function(function_symbol) => function_symbol.declared_name(),
             Symbol::Parameter(parameter_symbol) => parameter_symbol.declared_name(),
             Symbol::Variable(variable_symbol) => variable_symbol.declared_name(),
@@ -21,6 +27,8 @@ impl Symbol {
 
     pub fn declared_name_owned(&self) -> Rc<str> {
         match self {
+            Symbol::Class(class_symbol) => class_symbol.declared_name_owned(),
+            Symbol::Field(field_symbol) => field_symbol.declared_name_owned(),
             Symbol::Function(function_symbol) => function_symbol.declared_name_owned(),
             Symbol::Parameter(parameter_symbol) => parameter_symbol.declared_name_owned(),
             Symbol::Variable(variable_symbol) => variable_symbol.declared_name_owned(),
@@ -29,11 +37,105 @@ impl Symbol {
 
     pub fn source_range(&self) -> Option<&SourceRange> {
         match self {
+            Symbol::Class(class_symbol) => class_symbol.source_range(),
+            Symbol::Field(field_symbol) => field_symbol.source_range(),
             Symbol::Function(function_symbol) => function_symbol.source_range(),
             Symbol::Parameter(parameter_symbol) => parameter_symbol.source_range(),
             Symbol::Variable(variable_symbol) => variable_symbol.source_range(),
         }
     }
+
+    pub fn unwrap_class_symbol(&self) -> &ClassSymbol {
+        match self {
+            Symbol::Class(class_symbol) => class_symbol,
+            _ => panic!("Attempt to unwrap {:?} as ClassSymbol", self),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct ClassSymbol {
+    declared_name: Rc<str>,
+    source_range: Option<SourceRange>,
+    fqn: Rc<str>,
+    is_extern: bool,
+    field_symbol_ids: HashMap<Rc<str>, SymbolId>,
+    method_symbol_ids: HashMap<Rc<str>, SymbolId>,
+}
+
+impl ClassSymbol {
+    pub fn new(
+        declared_name: Rc<str>,
+        source_range: Option<SourceRange>,
+        fqn: Rc<str>,
+        is_extern: bool,
+        field_symbol_ids: HashMap<Rc<str>, SymbolId>,
+        method_symbol_ids: HashMap<Rc<str>, SymbolId>,
+    ) -> Self {
+        Self {
+            declared_name,
+            source_range,
+            fqn,
+            is_extern,
+            field_symbol_ids,
+            method_symbol_ids,
+        }
+    }
+
+    pub fn declared_name(&self) -> &str {
+        &self.declared_name
+    }
+
+    pub fn declared_name_owned(&self) -> Rc<str> {
+        self.declared_name.clone()
+    }
+
+    pub fn source_range(&self) -> Option<&SourceRange> {
+        self.source_range.as_ref()
+    }
+
+    pub fn fqn(&self) -> &str {
+        &self.fqn
+    }
+
+    pub fn can_assign_from(&self, right: &ClassSymbol, _ctx: &AnalysisContext) -> bool {
+        self.fqn == right.fqn // eventually, this will check inheritance logic, etc.
+    }
+
+    pub fn field_symbol_ids(&self) -> &HashMap<Rc<str>, SymbolId> {
+        &self.field_symbol_ids
+    }
+
+    pub fn method_symbol_ids(&self) -> &HashMap<Rc<str>, SymbolId> {
+        &self.method_symbol_ids
+    }
+}
+
+#[derive(Debug)]
+pub struct FieldSymbol {
+    declared_name: Rc<str>,
+    declared_name_source_range: Option<SourceRange>,
+}
+
+impl FieldSymbol {
+    pub fn new(declared_name: Rc<str>, source_range: Option<SourceRange>) -> Self {
+        Self {
+            declared_name,
+            declared_name_source_range: source_range,
+        }
+    }
+
+    pub fn declared_name(&self) -> &str {
+        &self.declared_name
+    }
+
+    pub fn declared_name_owned(&self) -> Rc<str> {
+        self.declared_name.clone()
+    }
+
+    pub fn source_range(&self) -> Option<&SourceRange> {
+        self.declared_name_source_range.as_ref()
+    }
 }
 
 #[derive(Debug)]
@@ -42,6 +144,7 @@ pub struct FunctionSymbol {
     declared_name_source_range: Option<SourceRange>,
     fqn: Rc<str>,
     is_extern: bool,
+    is_method: bool,
 }
 
 impl FunctionSymbol {
@@ -50,12 +153,14 @@ impl FunctionSymbol {
         declared_name_source_range: Option<SourceRange>,
         fqn: Rc<str>,
         is_extern: bool,
+        is_method: bool,
     ) -> Self {
         Self {
             declared_name,
             declared_name_source_range,
             fqn,
             is_extern,
+            is_method,
         }
     }
 
@@ -82,6 +187,10 @@ impl FunctionSymbol {
     pub fn is_extern(&self) -> bool {
         self.is_extern
     }
+
+    pub fn is_method(&self) -> bool {
+        self.is_method
+    }
 }
 
 #[derive(Debug)]

dmc-lib/src/semantic_analysis/type_info.rs

@@ -1,4 +1,5 @@
-use std::fmt::{Display, Formatter};
+use crate::semantic_analysis::analysis_context::AnalysisContext;
+use crate::semantic_analysis::symbol::SymbolId;
 
 pub type TypeInfoId = usize;
 
@@ -6,6 +7,7 @@ pub type TypeInfoId = usize;
 pub enum TypeInfo {
     Any,
     Function(FunctionTypeInfo),
+    Instance(InstanceTypeInfo),
     String,
     Int,
     Double,
@@ -13,35 +15,23 @@ pub enum TypeInfo {
     __Error,
 }
 
-impl Display for TypeInfo {
-    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(
-            f,
-            "{}",
-            match self {
-                TypeInfo::Any => "Any",
-                TypeInfo::Function(_) => "Function",
-                TypeInfo::String => "String",
-                TypeInfo::Int => "Int",
-                TypeInfo::Double => "Double",
-                TypeInfo::Void => "Void",
-                TypeInfo::__Error => panic!("This should never be shown to a user."),
-            }
-        )
-    }
-}
-
 #[derive(Clone, Debug)]
 pub struct FunctionTypeInfo {
     parameter_type_info_ids: Vec<TypeInfoId>,
     return_type_info_id: TypeInfoId,
+    self_type_info_id: Option<TypeInfoId>,
 }
 
 impl FunctionTypeInfo {
-    pub fn new(parameter_type_info_ids: Vec<TypeInfoId>, return_type_info_id: TypeInfoId) -> Self {
+    pub fn new(
+        parameter_type_info_ids: Vec<TypeInfoId>,
+        return_type_info_id: TypeInfoId,
+        self_type_info_id: Option<TypeInfoId>,
+    ) -> Self {
         Self {
             parameter_type_info_ids,
             return_type_info_id,
+            self_type_info_id,
         }
     }
 
@@ -52,4 +42,29 @@ impl FunctionTypeInfo {
     pub fn return_type_id(&self) -> TypeInfoId {
         self.return_type_info_id
     }
+
+    pub fn self_type_id(&self) -> Option<TypeInfoId> {
+        self.self_type_info_id
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct InstanceTypeInfo {
+    class_symbol_id: SymbolId,
+}
+
+impl InstanceTypeInfo {
+    pub fn new(class_symbol_id: SymbolId) -> Self {
+        Self { class_symbol_id }
+    }
+
+    pub fn class_symbol_id(&self) -> SymbolId {
+        self.class_symbol_id
+    }
+
+    pub fn can_assign_from(&self, right: &InstanceTypeInfo, ctx: &AnalysisContext) -> bool {
+        let self_class_symbol = ctx.symbols()[self.class_symbol_id].unwrap_class_symbol();
+        let right_class_symbol = ctx.symbols()[right.class_symbol_id].unwrap_class_symbol();
+        self_class_symbol.can_assign_from(right_class_symbol, ctx)
+    }
 }

e2e-tests/src/lib.rs

@@ -3,10 +3,12 @@ mod e2e_tests {
     use dmc_lib::compile_compilation_unit;
     use dmc_lib::constants_table::ConstantsTable;
     use dmc_lib::diagnostic::{Diagnostic, Diagnostics};
+    use dmc_lib::intrinsics::add_primitive_symbols_and_type_infos;
     use dmc_lib::semantic_analysis::analysis_context::AnalysisContext;
     use dvm_lib::vm::constant::{Constant, StringConstant};
     use dvm_lib::vm::value::Value;
     use dvm_lib::vm::{DvmContext, call};
+    use std::error::Error;
     use std::rc::Rc;
 
     const REGISTER_COUNT: usize = 16;
@@ -25,6 +27,9 @@ mod e2e_tests {
 
     fn prepare_context(input: &str) -> Result<DvmContext, Diagnostics> {
         let mut ctx = AnalysisContext::new();
+        let global_scope_id = ctx.push_scope("global");
+        add_primitive_symbols_and_type_infos(&mut ctx, global_scope_id);
+
         let mut constants_table = ConstantsTable::new();
 
         let compile_compilation_unit_result =
@@ -224,4 +229,31 @@ mod e2e_tests {
         assert_eq!(o.fields()[0].unwrap_int(), 42);
         Ok(())
     }
+
+    #[test]
+    fn string_len() -> Result<(), Diagnostics> {
+        fn core_string_len(args: &[Value]) -> Result<Value, Box<dyn Error>> {
+            let this = args[0].unwrap_string();
+            let len = this.len();
+            Ok(Value::Int(len.try_into()?))
+        }
+
+        let mut context = prepare_context(
+            "
+            fn main() -> Int
+                \"Hello, World!\".len()
+            end
+        ",
+        )?;
+
+        context
+            .platform_functions_mut()
+            .insert("core::String::len".into(), core_string_len);
+        let result = get_result(&context, "main", &vec![]);
+
+        assert!(result.is_some());
+        let value = result.unwrap();
+        assert!(matches!(value, Value::Int(13)));
+        Ok(())
+    }
 }