Refactor codegen into interchangeable passes

src/bin/bolt.ts

@@ -14,7 +14,7 @@ import { Checker } from "../checker"
 import { SourceFile, TextFile } from "../cst"
 import { parseSourceFile } from ".."
 import { Analyser } from "../analysis"
-import { Program } from "../program"
+import { Program, TargetType } from "../program"
 
 function debug(value: any) {
   console.error(util.inspect(value, { colors: true, depth: Infinity }));
@@ -37,7 +37,6 @@ yargs
       const cwd = args.C;
       const filename = path.resolve(cwd, args.file);
 
-      const diagnostics = new ConsoleDiagnostics();
       const program = new Program([ filename ]);
       if (program.diagnostics.hasError) {
         process.exit(1);
@@ -46,7 +45,7 @@ yargs
       if (program.diagnostics.hasError) {
         process.exit(1);
       }
-      program.emit();
+      program.emit({ type: TargetType.JS });
       if (program.diagnostics.hasError) {
         process.exit(1);
       }

src/codegen.ts

@@ -1,82 +0,0 @@
-
-import { CBuiltinType, CBuiltinTypeKind, CCallExpr, CConstExpr, CDecl, CDir, CExpr, CExprStmt, CFuncDecl, CIncDir, CProgram, CRefExpr, CStmt } from "./cast";
-import { Expression, SourceFile, Syntax, SyntaxKind } from "./cst";
-import { assert } from "./util";
-
-interface Context {
-  body: CStmt[];
-}
-
-export function generateCode(sourceFile: SourceFile): CProgram {
-
-  const intType = new CBuiltinType(CBuiltinTypeKind.Int);
-
-  const decls: (CDecl | CDir)[] = [];
-
-  decls.push(new CIncDir("runtime.h"));
-
-  const mainBody: CStmt[] = [];
-
-  decls.push(
-    new CFuncDecl(
-      intType,
-      'main',
-      [],
-      mainBody
-    )
-  );
-
-  visit(sourceFile, { body: mainBody });
-
-  return new CProgram(decls);
-
-  function visit(node: Syntax, context: Context): void {
-
-    switch (node.kind) {
-
-      case SyntaxKind.SourceFile:
-      {
-        for (const element of node.elements) {
-          visit(element, context);
-        }
-        break;
-      }
-
-      case SyntaxKind.ExpressionStatement:
-      {
-        context.body.push(
-          new CExprStmt(
-            visitExpression(node.expression, context)
-          )
-        );
-        break;
-      }
-
-      case SyntaxKind.LetDeclaration:
-      {
-        // TODO
-        break;
-      }
-
-    }
-
-  }
-
-  function visitExpression(node: Expression, context: Context): CExpr {
-    switch (node.kind) {
-      case SyntaxKind.ReferenceExpression:
-        assert(node.modulePath.length === 0);
-        return new CRefExpr(node.name.text);
-      case SyntaxKind.CallExpression:
-        const operator = visitExpression(node.func, context);
-        const args = node.args.map(arg => visitExpression(arg, context));
-        return new CCallExpr(operator, args);
-      case SyntaxKind.ConstantExpression:
-        return new CConstExpr(node.token.getValue());
-      default:
-        throw new Error(`Unexpected ${node}`);
-    }
-  }
-
-}
-

src/js.ts

@@ -0,0 +1,196 @@
+
+import type stream from "stream"
+import { IndentWriter } from "./util";
+
+export const enum JSNodeKind {
+
+  // Patterns
+  BindPattern,
+  ArrayPattern,
+  ObjectPattern,
+
+  // Expressions
+  ReferenceExpression,
+  CallExpression,
+  FunctionExpression,
+  MemberExpression,
+  IndexExpression,
+
+  // Statements
+  ExpressionStatement,
+  ReturnStatement,
+
+  // Declarations
+  FunctionDeclaration,
+  VariableDeclaration,
+
+  // Other nodes
+  Program,
+}
+
+abstract class JSNodeBase {
+
+  public abstract readonly kind: JSNodeKind;
+
+  public emit(out: stream.Writable): void {
+    const emitter = new JSEmitter(out);
+    emitter.emit(this as unknown as JSNode);
+  }
+
+}
+
+export class JSBindPattern extends JSNodeBase {
+
+  public readonly kind = JSNodeKind.BindPattern;
+
+  public constructor(
+    public name: string,
+  ) {
+    super();
+  }
+
+}
+
+export type JSPattern
+  = JSBindPattern
+
+export class JSReferenceExpression extends JSNodeBase {
+
+  public kind = JSNodeKind.ReferenceExpression;
+
+  public constructor(
+    public name: string,
+  ) {
+    super();
+  }
+
+}
+
+export class JSCallExpression extends JSNodeBase {
+
+  public readonly kind = JSNodeKind.CallExpression;
+
+  public constructor(
+    public operator: JSExpression,
+    public args: JSExpression[],
+  ) {
+    super();
+  }
+
+}
+
+export type JSExpression
+  = JSReferenceExpression
+  | JSCallExpression
+
+export class JSExpressionStatement extends JSNodeBase {
+
+  public readonly kind = JSNodeKind.ExpressionStatement;
+
+  public constructor(
+    public expression: JSExpression,
+  ) {
+    super();
+  }
+
+}
+
+export class JSReturnStatement extends JSNodeBase {
+
+  public readonly kind = JSNodeKind.ReturnStatement;
+
+  public constructor(
+    public value: JSExpression | null,
+  ) {
+    super();
+  }
+
+}
+
+export type JSStatement
+  = JSExpressionStatement
+  | JSReturnStatement
+
+export const enum JSDeclarationFlags {
+  IsExported = 1,
+}
+
+export type JSFunctionElement
+  = JSDeclaration
+  | JSStatement
+
+export class JSFunctionDeclaration extends JSNodeBase {
+
+  public readonly kind = JSNodeKind.FunctionDeclaration;
+
+  public constructor(
+    public flags: JSDeclarationFlags,
+    public name: string,
+    public params: JSPattern[],
+    public body: JSFunctionElement[],
+  ) {
+    super();
+  }
+
+}
+
+export enum JSVarType {
+  Var,
+  Const,
+  Let,
+}
+
+export class JSVariableDeclaration extends JSNodeBase {
+
+  public readonly kind = JSNodeKind.VariableDeclaration;
+
+  public constructor(
+    public flags: JSDeclarationFlags,
+    public varType: JSVarType,
+    public pattern: JSPattern,
+    public value: JSExpression | null,
+  ) {
+    super();
+  }
+
+}
+
+export type JSDeclaration
+  = JSFunctionDeclaration
+  | JSVariableDeclaration
+
+export type JSSourceElement
+  = JSStatement
+  | JSDeclaration
+
+export class JSProgram extends JSNodeBase {
+  
+  public readonly kind = JSNodeKind.Program;
+
+  public constructor(
+    public elements: JSSourceElement[],
+  ) {
+    super();
+  }
+
+}
+
+export type JSNode
+  = JSStatement
+  | JSDeclaration
+  | JSExpression
+  | JSPattern
+  | JSProgram
+
+export class JSEmitter {
+
+  private writer: IndentWriter;
+
+  public constructor(out: stream.Writable) {
+    this.writer = new IndentWriter(out);
+  }
+
+  public emit(node: JSNode) {
+  }
+
+}

src/passes/BoltToC.ts

@@ -0,0 +1,90 @@
+
+import { CBuiltinType, CBuiltinTypeKind, CCallExpr, CConstExpr, CDecl, CDir, CExpr, CExprStmt, CFuncDecl, CIncDir, CNode, CProgram, CRefExpr, CStmt } from "../c";
+import { Expression, Syntax, SyntaxKind } from "../cst";
+import { Pass } from "../types";
+import { assert } from "../util";
+
+interface Context {
+  body: CStmt[];
+}
+
+class BoltToC implements Pass<Syntax, CNode> {
+
+  public apply(input: Syntax): CNode {
+
+    assert(input.kind === SyntaxKind.SourceFile);
+
+    const intType = new CBuiltinType(CBuiltinTypeKind.Int);
+
+    const decls: (CDecl | CDir)[] = [];
+
+    decls.push(new CIncDir("runtime.h"));
+
+    const mainBody: CStmt[] = [];
+
+    decls.push(
+      new CFuncDecl(
+        intType,
+        'main',
+        [],
+        mainBody
+      )
+    );
+
+    visit(input, { body: mainBody });
+
+    return new CProgram(decls);
+
+    function visit(node: Syntax, context: Context): void {
+
+      switch (node.kind) {
+
+        case SyntaxKind.SourceFile:
+        {
+          for (const element of node.elements) {
+            visit(element, context);
+          }
+          break;
+        }
+
+        case SyntaxKind.ExpressionStatement:
+        {
+          context.body.push(
+            new CExprStmt(
+              visitExpression(node.expression, context)
+            )
+          );
+          break;
+        }
+
+        case SyntaxKind.LetDeclaration:
+        {
+          // TODO
+          break;
+        }
+
+      }
+
+    }
+
+    function visitExpression(node: Expression, context: Context): CExpr {
+      switch (node.kind) {
+        case SyntaxKind.ReferenceExpression:
+          assert(node.modulePath.length === 0);
+          return new CRefExpr(node.name.text);
+        case SyntaxKind.CallExpression:
+          const operator = visitExpression(node.func, context);
+          const args = node.args.map(arg => visitExpression(arg, context));
+          return new CCallExpr(operator, args);
+        case SyntaxKind.ConstantExpression:
+          return new CConstExpr(node.token.getValue());
+        default:
+          throw new Error(`Unexpected ${node}`);
+      }
+    }
+
+  }
+
+}
+
+export default BoltToC;

src/passes/BoltToJS.ts

@@ -0,0 +1,14 @@
+import { Syntax } from "../cst";
+import { JSNode, JSProgram } from "../js";
+import { Pass } from "../types";
+
+export class BoltToJS implements Pass<Syntax, JSNode> {
+
+  public apply(input: Syntax): JSNode {
+    return new JSProgram([]);
+  }
+
+}
+
+export default BoltToJS;
+

src/program.ts

@@ -5,8 +5,39 @@ import { SourceFile, TextFile } from "./cst";
 import { ConsoleDiagnostics, Diagnostics } from "./diagnostics";
 import { Checker } from "./checker";
 import { Analyser } from "./analysis";
-import { generateCode } from "./codegen";
-import { CEmitter } from "./cast";
+import { Newable, Pass } from "./types";
+import BoltToC from "./passes/BoltToC";
+import BoltToJS from "./passes/BoltToJS";
+
+type AnyPass = Pass<any, any>;
+
+export enum TargetType {
+  C,
+  JS,
+  WebAssembly,
+  LLVM,
+}
+
+interface TargetSpec {
+  type: TargetType;
+}
+
+export class PassManager {
+
+  private registeredPasses: AnyPass[] = [];
+
+  public add(pass: Newable<AnyPass>) {
+    this.registeredPasses.push(new pass());
+  }
+
+  public apply<In>(input: In): unknown {
+    for (const pass of this.registeredPasses) {
+      input = pass.apply(input);
+    }
+    return input;
+  }
+
+}
 
 export class Program {
 
@@ -41,11 +72,23 @@ export class Program {
     }
   }
 
-  public emit(): void {
+  public emit(target: TargetSpec): void {
+    let suffix;
+    const passes = new PassManager();
+    switch (target.type) {
+      case TargetType.C:
+        suffix = '.c';
+        passes.add(BoltToC);
+        break;
+      case TargetType.JS:
+        suffix = '.js'
+        passes.add(BoltToJS);
+        break;
+    }
     for (const [filePath, sourceFile] of this.sourceFilesByPath) {
-      const file = fs.createWriteStream(stripExtension(filePath) + '.c', 'utf-8'); 
-      const emitter = new CEmitter(file);
-      emitter.emit(generateCode(sourceFile));
+      const code = passes.apply(sourceFile) as any;
+      const file = fs.createWriteStream(stripExtension(filePath) + suffix, 'utf-8'); 
+      code.emit(file);
     }
   }
 

src/types.ts

@@ -0,0 +1,8 @@
+
+export interface Pass<In, Out> {
+  apply(input: In): Out;
+}
+
+export interface Newable<T> {
+  new (...args: any[]): T;
+}