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43 lines
2.4 KiB
Markdown
43 lines
2.4 KiB
Markdown
# Architecture of `ergc`
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## 1. Scan an Erg script (.er) and generate a `TokenStream` (parser/lex.rs)
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* parser/lexer/Lexer generates `TokenStream` (this is an iterator of `Token`, `TokenStream` can be generated by `Lexer::collect()`)
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* `Lexer` is constructed from `Lexer::new` or `Lexer::from_str`, where `Lexer::new` reads the code from a file or command option.
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* `Lexer` can generate tokens sequentially as an iterator; if you want to get a `TokenStream` all at once, use `Lexer::lex`.
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* `Lexer` outputs `LexError`s as errors, but `LexError` does not have enough information to display itself. If you want to display the error, use the `LexerRunner` to convert the error.
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* `LexerRunner` can also be used if you want to use `Lexer` as standalone; `Lexer` is just an iterator and does not implement the `Runnable` trait.
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* `Runnable` is implemented by `LexerRunner`, `ParserRunner`, `Compiler`, and `DummyVM`.
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## 2. Convert `TokenStream` -> `AST` (parser/parse.rs)
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* `Parser`, like `Lexer`, has two constructors, `Parser::new` and `Parser::from_str`, and `Parser::parse` will give the `AST`.
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* `AST` is the wrapper type of `Vec<Expr>`. It is for "Abstract Syntax Tree".
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### 2.1 Desugaring `AST`
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* expand nested vars (`Desugarer::desugar_nest_vars_pattern`)
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* desugar multiple pattern definition syntax (`Desugarer::desugar_multiple_pattern_def`)
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### 2.2 Reordering & Linking `AST`
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* Sort variables according to dependencies and link class methods to class definitions (`Linker::link`)
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## 3. Type checking & inference, Convert `AST` -> `HIR` (compiler/lower.rs)
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* `HIR` has every variable's type information. It is for "High-level Intermediate Representation".
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* `ASTLowerer` can be constructed in the same way as `Parser` and `Lexer`.
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* `ASTLowerer::lower` will output a tuple of `HIR` and `CompileWarnings` if no errors occur.
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* `ASTLowerer` is owned by `Compiler`. Unlike conventional structures, `ASTLowerer` handles code contexts and is not a one-time disposable.
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* If the result of type inference is incomplete (if there is an unknown type variable), an error will occur during name resolution.
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## 4. Check side-effects (compiler/effectcheck.rs)
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## 4. Check ownerships (compiler/memcheck.rs)
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## 5. Generate Bytecode (`CodeObj`) from `HIR` (compiler/codegen.rs)
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## (6. (Future plans) Convert Bytecode -> LLVM IR)
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* Bytecode is stack-based, whereas LLVM IR is register-based.
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There will be several more layers of intermediate processes for this conversion process.
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