Compiler

This page contains a high level breakdown of the different steps needed to compile Mew code.

1. AST Parsing

The parsing step iterates through all source files, and builds a syntax tree for each of them.
The syntax tree represents the code as it was written, maintaining the trivia such as white space, comments etc.

Each node in the AST has a reference to both it's parent and children.

Apart from being the basis for HIR generation, the AST is also used to interact with the source code programatically, i.e. from the LSP server.

2. HIR generation

HIR, short for High-level Intermediate Representation, represents a bound tree, where all types are known.

The HIR references resolved symbols for the different parts of Mew (namespaces, types, functions, parameters, variables etc). For example, two code block that calls a function, will have the same symbol reference to that function.

1. Build symbol table
   1. Namespaces
   2. Types
   3. Free functions
   4. Type members
2. Binding
   1. Types
   2. Free functions
   3. Top level statements

info

HIR might contain errors, represented as error symbols.

3. MIR generation

MIR, short for Medium-level Intermediate Representation, is a lowered HIR, without constructs such as while/loop/if.

All higher level constructs such as loops and conditions been lowered into labels and branches.

Control flow analysis and some optimizations are done here as well.

info

MIR might contain errors, represented as error symbols.

4. LIR generation

LIR, short for Low-level Intermediate Representation, is a lowered MIR, resembling the final byte code that will be emitted.

warning

LIR MUST NOT contain any errors.

5. Emitting

Finally, the LIR is transpiled into C# and compiled to native assembly code using NativeAOT, which in turn can be executed.

note

There are plans in the future to emit CIL directly.
This was done in the early prototype, but turned out to be too cumbersome while the language was in active development.