Brett Language Server & Compiler

Naam student: Brett Deswert
Vak: Programmeren 3 – 2025–2026

Dit project bevat een compiler en een VS Code Language Server Extension voor de zelf ontworpen programmeertaal Brett.

De focus ligt op:
- Diagnostics (syntax & semantiek)
- Code completion
- Een duidelijke grammatica (EBNF)
- Integratie met VS Code via LSP

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Projectstructuur

Compiler Project

``
Compiler/
├─ .idea/
├─ dist/
├─ node_modules/
├─ pictures/
├─ src/
├─ test/
├─ .gitignore
├─ antlr-4.13.2-complete.jar
├─ generate-compiler.js
├─ generate-compiler.ps1
├─ package.json
├─ package-lock.json
├─ README.md
└─ vite.config.js
`

Extension Project

`
EXTENSION/
├─ .vscode/
├─ client/
│ ├─ node_modules/
│ ├─ out/
│ ├─ src/
│ │ └─ test/
│ │ └─ extension.ts
│ ├─ testFixture/
│ ├─ package-lock.json
│ ├─ package.json
│ ├─ tsconfig.json
│ └─ tsconfig.tsbuildinfo
├─ scripts/
│ └─ e2e.sh
├─ server/
│ ├─ node_modules/
│ ├─ out/
│ └─ src/
│ └─ server.ts
├─ .gitignore
├─ eslint.config.mjs
├─ package-lock.json
├─ package.json
├─ tsconfig.json
├─ tsconfig.tsbuildinfo
├─ README.md
└─ tsconfig.json
`


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Build & Run

$3


`bash
cd Compiler
npm ci --include=dev
npm run build
`

Dit voert automatisch uit:
- generatie van de parser via ANTLR (antlrci)
- build van de compiler naar Compiler/dist/

De gegenereerde code wordt gebruikt door de SemanticAnalyserVisitor.

---

$3


`bash
cd Compiler
npm ci --include=dev
npm run antlrci
npm test
`

---

$3

`bash
cd extension
npm install
npm run compile
`
De package.json haalt de package op via npm, en gebruikt de geuploade package.

De package wordt bij elke build automatisch naar npm geupload.

Dit is een link naar de npm package: https://www.npmjs.com/package/brett-compiler

Start daarna de extension via Run Extension in VS Code.

---

Voorbeeldbroncode (alle ondersteunde syntax)

`brett
let count: number = 10;
const isActive: bool = true;
let message: string = "Hallo Brett";

def add(a: number, b: number): number {
return a + b;
}

let result = add(5, 7);

if (result > 10) {
message = "Groter dan tien";
} else {
message = "Tien of kleiner";
}

while (count > 0) {
count--;
}

for (let i: number = 0; i < 5; i = i + 1) {
result = result + i;
}

do {
count++;
} while (count < 3);

switch {
case result == 0 => {
message = "Nul";
}
default => {
message = "Niet nul";
}
}

let numbers = [1, 2, 3];
let person = {
name: "Alice",
age: 30
};

try {
let value = numbers[10];
} catch (err: any) {
message = "Fout opgetreden";
} finally {
message = "Klaar";
}
`

---

Diagnostics

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- Ontbrekende ;
- Foutieve blokstructuur
- Ongeldige expressies

Worden weergegeven als Error diagnostics.

---

$3

- Typefouten
`brett
let x: number = "tekst";
`
- Dubbele declaraties in dezelfde scope
- Ongekende functies of variabelen

---

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- Naamgevingsconventies
`brett
let MyAge: number = 30;
`

Errors en warnings werken rond verschillende semantiek (types, scope, naamgeving).

---

Code Completion

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- Variabelen
- Functies
- Parameters
- Types
- Keywords (let, const, def, return, if, while, …)

$3

- if...else
- def-func

Functies worden automatisch aangevuld met ().

---

Grammatica (EBNF)

`ebnf
program = { statement } ;
block = "{" { statement } "}" ;

statement = variableDeclaration
| functionDeclaration
| ifStatement
| whileStatement
| forStatement
| switchStatement
| returnStatement
| expressionStatement
| block
| breakStatement
| continueStatement
| doWhileStatement
| tryCatchStatement ;

variableDeclaration
= "let" IDENTIFIER [ ":" type ] [ "=" expression ] ";"
| "const" IDENTIFIER ":" type "=" expression ";" ;

functionDeclaration
= "def" IDENTIFIER "(" [ parameterList ] ")" [ ":" type ] block ;

parameterList = parameter { "," parameter } ;
parameter = IDENTIFIER [ ":" type ] ;

ifStatement = "if" "(" expression ")" block [ "else" block ] ;
whileStatement = "while" "(" expression ")" block ;
doWhileStatement = "do" block "while" "(" expression ")" ";" ;
forStatement = "for" "(" [ variableDeclaration | expressionStatement ]
[ expression ] ";" [ expression ] ")" block ;

switchStatement = "switch" "{" { switchCase } [ defaultCase ] "}" ;
switchCase = "case" expression "=>" block ;
defaultCase = "default" "=>" block ;

tryCatchStatement = "try" block "catch" "(" IDENTIFIER [ ":" type ] ")" block
[ "finally" block ] ;

returnStatement = "return" [ expression ] ";" ;
breakStatement = "break" ";" ;
continueStatement = "continue" ";" ;
expressionStatement = expression ";" ;

type = baseType { "[]" } ;
baseType = "string" | "number" | "bool" | "any" | "void" | IDENTIFIER ;

expression = assignment ;
assignment = [ IDENTIFIER "=" ] comparison ;
comparison = term { ( "==" | "!=" | "<" | "<=" | ">" | ">=" ) term } ;
term = factor { ( "+" | "-" ) factor } ;
factor = unary { ( "*" | "/" ) unary } ;
unary = ( "++" | "--" ) unary | postfix ;
postfix = primary { "++" | "--" | "[" expression "]" | "." IDENTIFIER } ;

primary = NUMBER
| STRING
| "true"
| "false"
| "nil"
| IDENTIFIER
| "(" expression ")"
| IDENTIFIER "(" [ argList ] ")"
| arrayLiteral
| objectLiteral
| "new" IDENTIFIER "(" [ argList ] ")" ;

arrayLiteral = "[" [ expression { "," expression } ] "]" ;
objectLiteral = "{" [ property { "," property } ] "}" ;
property = ( IDENTIFIER | STRING ) ":" expression ;
argList = expression { "," expression } ;
`

(Volledige grammatica wordt geïmplementeerd via ANTLR.)

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Compiler-architectuur

- Lexer + Parser: ANTLR
- Opbouw van CST
- Semantische analyse:
- symbol tables
- scope-analyse
- type checking
- Gestructureerde foutafhandeling met locatie-informatie

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VS Code Language Server

- Zet compiler-resultaten om naar:
- Diagnostics in de editor
- Completion items
- Gebruikt vscode-languageserver

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Testing

- Unit tests voor parser (CST)
- Tests voor syntax errors
- End-to-end tests voor semantische analyse
- End-to-end tests voor code completion data

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Code om warnings en errors mee te testen

De volgende code moet geschreven worden in een bestand genaamd index.brett om de verschillende warnings, errors en code completions te testen.

`brett
// ===================================
// SECTION 1: SYNTAX ERRORS
// ===================================

let x: number = 10;
const MyVariable: any = 5;

def calculate(a: number, b: number) {
return a + b;
}

if (true) {
let z = 5;
}



// ===================================
// SECTION 2: SEMANTIC ERRORS
// ===================================

let MyAge: number = 30; // (Warning)

let myValue: number = "hello"; // ERROR 6

def testScope() {
let localVar: number = 1;
let localVar: string = "oops"; // ERROR 7
}

def anotherFunction() {
let result = calculate(10, 20);

// 👇 FOUTEN DIE MOETEN VERSCHIJNEN
let total = sum(1, 2); // Function 'sum' is not found.

total = unknown + 1; // Variable 'unknown' is niet gevonden in deze scope.
}
``

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Screenshots

- error diagnostics
!error diagnostics

- warning diagnostics
!warning diagnostics

- completion popup in VS Code

!code completion popup 2
!code completion popup 1
!code completion popup 3

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