Improve symbol resolution algorithms in type checker

src/ast-spec.txt

@@ -277,7 +277,7 @@ node BoltPlainImportSymbol > BoltImportSymbol {
 
 node BoltImportDirective > BoltSourceElement {
   modifiers: BoltModifiers,
-  file: String,
+  file: BoltStringLiteral,
   symbols: Vec<BoltImportSymbol>,
 }
 

src/ast.d.ts

@@ -1,8 +1,28 @@
 
+import { Type } from "./types"
+import { ScopeInfo } from "./checker"
 import { Package } from "./common"
+import { TextSpan } from "./text"
+
+export function setParents(node: Syntax): void;
+
+export type SyntaxRange = [Syntax, Syntax];
 
 export function isSyntax(value: any): value is Syntax;
 
+interface SyntaxBase<K extends SyntaxKind> {
+  id: number;
+  _scope?: ScopeInfo;
+  kind: K;
+  parentNode: ParentTypesOf<K> | null;
+  span: TextSpan | null;
+  getChildNodes(): IterableIterator<ChildTypesOf<K>>,
+  findAllChildrenOfKind<K1 extends SyntaxKind>(kind: K1): IterableIterator<ResolveSyntaxKind<K1>>;
+}
+
+export type ResolveSyntaxKind<K extends SyntaxKind> = Extract<Syntax, { kind: K }>;
+
+
 
 export const enum SyntaxKind {
   EndOfFile = 2,
@@ -158,25 +178,6 @@ export const enum SyntaxKind {
   JSSourceFile = 182,
 }
 
-
-
-import { TextSpan } from "./text"
-
-export function setParents(node: Syntax): void;
-
-export type SyntaxRange = [Syntax, Syntax];
-
-interface SyntaxBase<K extends SyntaxKind> {
-  id: number;
-  kind: K;
-  parentNode: ParentTypesOf<K> | null;
-  span: TextSpan | null;
-  getChildNodes(): IterableIterator<ChildTypesOf<K>>,
-  findAllChildrenOfKind<K1 extends SyntaxKind>(kind: K1): IterableIterator<ResolveSyntaxKind<K1>>;
-}
-
-export type ResolveSyntaxKind<K extends SyntaxKind> = Extract<Syntax, { kind: K }>;
-
 export interface EndOfFile extends SyntaxBase<SyntaxKind.EndOfFile> {
   kind: SyntaxKind.EndOfFile;
 }
@@ -824,7 +825,7 @@ export interface BoltPlainImportSymbol extends SyntaxBase<SyntaxKind.BoltPlainIm
 export interface BoltImportDirective extends SyntaxBase<SyntaxKind.BoltImportDirective> {
   kind: SyntaxKind.BoltImportDirective;
   modifiers: BoltModifiers;
-  file: string;
+  file: BoltStringLiteral;
   symbols: BoltImportSymbol[];
 }
 
@@ -1705,7 +1706,7 @@ export function createBoltModule(modifiers: BoltModifiers, name: BoltQualName, e
 export function createBoltFunctionDeclaration(modifiers: BoltModifiers, target: string, name: BoltSymbol, params: BoltParameter[], returnType: BoltTypeExpression | null, typeParams: BoltTypeParameter[] | null, body: BoltFunctionBodyElement[], span?: TextSpan | null): BoltFunctionDeclaration;
 export function createBoltVariableDeclaration(modifiers: BoltModifiers, bindings: BoltPattern, type: BoltTypeExpression | null, value: BoltExpression | null, span?: TextSpan | null): BoltVariableDeclaration;
 export function createBoltPlainImportSymbol(name: BoltQualName, span?: TextSpan | null): BoltPlainImportSymbol;
-export function createBoltImportDirective(modifiers: BoltModifiers, file: string, symbols: BoltImportSymbol[], span?: TextSpan | null): BoltImportDirective;
+export function createBoltImportDirective(modifiers: BoltModifiers, file: BoltStringLiteral, symbols: BoltImportSymbol[], span?: TextSpan | null): BoltImportDirective;
 export function createBoltExportSymbol(span?: TextSpan | null): BoltExportSymbol;
 export function createBoltPlainExportSymbol(name: BoltQualName, span?: TextSpan | null): BoltPlainExportSymbol;
 export function createBoltExportDirective(file: string, symbols: BoltExportSymbol[] | null, span?: TextSpan | null): BoltExportDirective;

src/bin/bolt.ts

@@ -36,11 +36,6 @@ function pushAll<T>(array: T[], elements: T[]) {
   }
 }
 
-function stripExtension(filepath: string) {
-  const i = filepath.lastIndexOf('.');
-  return i !== -1 ? filepath.substring(0, i) : filepath
-}
-
 function flatMap<T>(array: T[], proc: (element: T) => T[]) {
   let out: T[] = []
   for (const element of array) {
@@ -123,6 +118,7 @@ function loadPackageMetadata(rootDir: string) {
 }
 
 function loadPackage(rootDir: string): Package {
+  rootDir = path.resolve(rootDir);
   const data = loadPackageMetadata(rootDir);
   const pkg = new Package(rootDir, data.name, data.version, []);
   for (const filepath of globSync(path.join(rootDir, '**/*.bolt'))) {
@@ -132,13 +128,14 @@ function loadPackage(rootDir: string): Package {
 }
 
 function loadPackagesAndSourceFiles(filenames: string[], cwd = '.'): Package[] {
+  cwd = path.resolve(cwd);
   const anonPkg = new Package(cwd, null, null, []);
   const pkgs = [ anonPkg ];
   for (const filename of filenames) {
     if (fs.statSync(filename).isDirectory()) {
       pkgs.push(loadPackage(filename));
     } else {
-      anonPkg.addSourceFile(parseSourceFile(filename, anonPkg, 0));
+      anonPkg.addSourceFile(parseSourceFile(filename, anonPkg));
     }
   }
   return pkgs;

src/checker.ts

@@ -42,9 +42,12 @@ import {
   isBoltStatement,
   isBoltDeclaration,
   isSourceFile,
-  BoltReferenceTypeExpression
+  BoltReferenceTypeExpression,
+  isBoltTypeDeclaration,
+  SourceFile,
+  BoltModifiers
 } from "./ast";
-import {FastStringMap, memoize, assert, verbose} from "./util";
+import {FastStringMap, countDigits, assert, verbose} from "./util";
 import {
   DiagnosticPrinter,
   E_TYPES_NOT_ASSIGNABLE,
@@ -52,157 +55,90 @@ import {
   E_TOO_FEW_ARGUMENTS_FOR_FUNCTION_CALL,
   E_TYPE_DECLARATION_NOT_FOUND,
   E_DECLARATION_NOT_FOUND,
-  E_INVALID_ARGUMENTS
+  E_INVALID_ARGUMENTS,
+  E_FILE_NOT_FOUND,
 } from "./diagnostics";
 import { createAnyType, isOpaqueType, createOpaqueType, Type, createVoidType, createVariantType, isVoidType } from "./types";
-import { getReturnStatementsInFunctionBody, isAutoImported, toDeclarationPath, createDeclarationPath, hasRelativeModulePath, hasAbsoluteModulePath, DeclarationPath, getModulePath, getSymbolNameOfDeclarationPath } from "./common";
+import { getReturnStatementsInFunctionBody, Package } from "./common";
 import {emit} from "./emitter";
+import {Program} from "./program";
+import {type} from "os";
 
-const PACKAGE_SCOPE_ID = 0;
+// TODO
+const GLOBAL_SCOPE_ID = 0;
+
+class SymbolPath {
+
+  constructor(
+    private parents: string[],
+    public isAbsolute: boolean,
+    public name: string
+  ) {
+
+  }
+
+  public hasParents(): boolean {
+    return this.parents.length > 0;
+  }
+
+  public getParents() {
+    return this.parents;
+  }
 
-interface SymbolInfo<N extends Syntax> {
-  declarations: N[];
 }
 
-function introducesNewScope(kind: SyntaxKind): boolean {
+function nodeToSymbolPath(node: BoltSyntax): SymbolPath {
-  return kind === SyntaxKind.BoltSourceFile
+  switch (node.kind) {
-      || kind === SyntaxKind.BoltModule
+    case SyntaxKind.BoltIdentifier:
-      || kind === SyntaxKind.BoltFunctionDeclaration
+      return new SymbolPath([], false, emit(node));
-      || kind === SyntaxKind.BoltBlockExpression;
+    case SyntaxKind.BoltQualName:
+      const name = emit(node.name);
+      if (node.modulePath === null) {
+        return new SymbolPath([], false, name);
+      }
+      return new SymbolPath(node.modulePath.map(id => id.text), false, name);
+    default:
+      throw new Error(`Could not extract a symbol path from the given node.`);
+  }
 }
 
-function introducesNewTypeScope(kind: SyntaxKind): boolean {
+enum SymbolKind {
-  return kind === SyntaxKind.BoltModule
+  Type     = 0x1,
-      || kind === SyntaxKind.BoltSourceFile;
+  Variable = 0x2,
+  Module   = 0x4,
 }
 
-type Scope = unknown;
+function* getAllSymbolKindsInMask(symbolKindMask: SymbolKind) {
-type TypeScope = unknown;
+  const n = countDigits(symbolKindMask, 2);
-
+  for (let i = 1; i <= n; i++) {
-function getScopeId(scope: Scope | TypeScope) {
+    if ((symbolKindMask & i) > 0) {
-  if (isSyntax(scope)) {
+      yield i;
-    return scope.id;
+    }
   }
-  return PACKAGE_SCOPE_ID;
 }
 
-function createSymbol(node: BoltDeclaration): SymbolInfo {
+export interface ScopeInfo {
-  return { declarations: [ node ] };
+  id: number;
+  declaration: BoltSyntax | Package;
+  parentScope?: ScopeInfo;
+  kind: SymbolKind,
 }
 
-class SymbolResolver<N extends Syntax> {
+interface SymbolInfo {
-
+  kind: SymbolKind;
-  private symbols = new FastStringMap<string, SymbolInfo<N>>();
+  declarations: BoltSyntax[];
-
-  constructor(private introducesNewScope: (kind: SyntaxKind) => boolean) {
-
-  }
-
-  public addSymbol(name: string, node: N): void {
-    const scope = this.getScopeSurroundingNode(node)
-    verbose(`Adding symbol ${name} in scope #${getScopeId(scope)}`);
-    const sym = { declarations: [ node ] };
-    this.symbols.set(`${name}@${getScopeId(scope)}`, sym);
-  }
-
-  public getParentScope(scope: Scope): Scope | null {
-    if (!isSyntax(scope)) {
-      // Scope is the global package scope
-      return null;
-    }
-    if (scope.kind === SyntaxKind.BoltSourceFile) {
-      return scope.package;
-    }
-    return this.getScopeForNode(scope.parentNode!)
-  }
-
-  public getScopeSurroundingNode(node: Syntax): Scope {
-    assert(node.parentNode !== null);
-    return this.getScopeForNode(node.parentNode!);
-  }
-
-  public getScopeForNode(node: Syntax): Scope {
-    let currNode = node;
-    while (!this.introducesNewScope(currNode.kind)) {
-      if (currNode.kind === SyntaxKind.BoltSourceFile) {
-        return currNode.package;
-      }
-      currNode = currNode.parentNode!;
-    }
-    return currNode;
-  }
-
-  private lookupSymbolInScope(name: string, scope: Scope): SymbolInfo<N> | null {
-    const key = `${name}@${getScopeId(scope)}`;
-    if (!this.symbols.has(key)) {
-      return null;
-    }
-    return this.symbols.get(key);
-  }
-
-  public findSymbolInScopeOf(name: string, scope: Scope): SymbolInfo<N> | null {
-    while (true) {
-      const sym = this.lookupSymbolInScope(name, scope);
-      if (sym !== null) {
-        return sym;
-      }
-      const parentScope = this.getParentScope(scope);
-      if (parentScope === null) {
-        break;
-      }
-      scope = parentScope;
-    }
-    return null;
-  }
-
-  public resolve(path: DeclarationPath, node: BoltSyntax): BoltSyntax | null {
-    let scope = this.getScopeSurroundingNode(node);
-    if (hasAbsoluteModulePath(path)) {
-      // TODO
-    } else if (hasRelativeModulePath(path)) {
-      while (true) {
-        let shouldSearchParentScopes = false;
-        let currScope = scope;
-        for (const name of getModulePath(path)) {
-          const sym = this.lookupSymbolInScope(name, currScope);
-          if (sym === null) {
-            shouldSearchParentScopes = true;
-            break;
-          }
-          if (sym.declarations[0].kind !== SyntaxKind.BoltModule) {
-            shouldSearchParentScopes = true;
-            break;
-          }
-          currScope = this.getScopeForNode(sym.declarations[0]);
-        }
-        if (!shouldSearchParentScopes) {
-          scope = currScope;
-          break;
-        }
-        const parentScope = this.getParentScope(scope);
-        if (parentScope === null) {
-          return null;
-        }
-        scope = parentScope;
-      }
-    }
-    const sym = this.findSymbolInScopeOf(getSymbolNameOfDeclarationPath(path), scope);
-    if (sym === null) {
-      return null;
-    }
-    return sym.declarations[0]!;
-  }
-
 }
 
 export class TypeChecker {
 
-  constructor(private diagnostics: DiagnosticPrinter) {
+  constructor(
+    private diagnostics: DiagnosticPrinter,
+    private program: Program
+  ) {
 
   }
 
-  private varResolver = new SymbolResolver<BoltDeclaration>(introducesNewScope);
+  private symbols = new FastStringMap<string, SymbolInfo>();
-  private typeResolver = new SymbolResolver<BoltTypeDeclaration>(introducesNewTypeScope);
 
   public checkSourceFile(node: BoltSourceFile): void {
 
@@ -314,14 +250,6 @@ export class TypeChecker {
 
       switch (node.kind) {
 
-        case SyntaxKind.BoltModule:
-        {
-          for (const element of node.elements) {
-            visitSourceElement(element);
-          }
-          break;
-        }
-
         case SyntaxKind.BoltRecordDeclaration:
         {
           if (node.members !== null) {
@@ -460,16 +388,15 @@ export class TypeChecker {
 
   }
 
-  private resolveType(name: string, node: BoltSyntax): Type | null {
+  private resolveTypeName(name: string, node: BoltSyntax): Type | null {
-    const sym = this.typeResolver.findSymbolInScopeOf(name, this.typeResolver.getScopeSurroundingNode(node))
+    const sym = this.findSymbolInScopeOf(name, this.getScopeSurroundingNode(node));
     if (sym === null) {
       return null;
     }
     return this.getTypeOfNode(sym.declarations[0]);
   }
 
-  @memoize(node => node.id)
+  private createType(node: BoltSyntax): Type {
-  private getTypeOfNode(node: BoltSyntax): Type {
     switch (node.kind) {
       case SyntaxKind.BoltReferenceTypeExpression:
       {
@@ -504,18 +431,18 @@ export class TypeChecker {
       }
       case SyntaxKind.BoltConstantExpression:
       {
-        let type;
+        return node.value.getType();
-        if (typeof node.value === 'string') {
+        //if (typeof node.value === 'string') {
-          type = this.resolveType('String', node)!;
+        //  type = this.resolveTypeName('String', node)!;
-        } else if (typeof node.value === 'boolean') {
+        //} else if (typeof node.value === 'boolean') {
-          type = this.resolveType('bool', node)!;
+        //  type = this.resolveTypeName('bool', node)!;
-        } else if (typeof node.value === 'bigint') {
+        //} else if (typeof node.value === 'bigint') {
-          type = this.resolveType('i32', node)!;
+        //  type = this.resolveTypeName('i32', node)!;
-        } else {
+        //} else {
-          throw new Error(`Could not derive type of constant expression.`);
+        //  throw new Error(`Could not derive type of constant expression.`);
-        }
+        //}
-        assert(type !== null);
+        //assert(type !== null);
-        return type;
+        //return type;
       }
       case SyntaxKind.BoltMatchExpression:
       {
@@ -526,6 +453,15 @@ export class TypeChecker {
     }
   }
 
+  private getTypeOfNode(node: BoltSyntax): Type {
+    if (node._type !== undefined) {
+      return node._type;
+    }
+    const type = this.createType(node);
+    node._type = type;
+    return type;
+  }
+
   private isTypeAssignableTo(left: Type, right: Type): boolean {
     if (isOpaqueType(left) &&  isOpaqueType(right)) {
       return left === right;
@@ -574,43 +510,316 @@ export class TypeChecker {
   }
 
   public registerSourceFile(node: BoltSourceFile): void {
-    this.addAllSymbolsInNode(node);
-  }
 
-  private addAllSymbolsInNode(node: BoltSyntax): void {
+    const self = this;
+
+    addAllSymbolsToScope(
+      node,
+      this.getScopeForNode(node, SymbolKind.Variable),
+      this.getScopeForNode(node, SymbolKind.Type),
+      this.getScopeForNode(node, SymbolKind.Module)
+    );
+
+    function addAllSymbolsToScope(node: BoltSyntax, variableScope: ScopeInfo, typeScope: ScopeInfo, moduleScope: ScopeInfo, allowDuplicates = false): void {
 
       switch (node.kind) {
 
+        case SyntaxKind.BoltImportDirective:
+        {
+          if (node.symbols !== null) {
+            for (const importSymbol of node.symbols) {
+              // TODO
+            }
+          } else {
+            const sourceFile = self.program.resolveToSourceFile(node.file.value, node) as BoltSourceFile;
+            if (sourceFile === null) {
+              self.diagnostics.add({
+                severity: 'error',
+                message: E_FILE_NOT_FOUND,
+                args: { filename: node.file.value },
+                node: node.file,
+              });
+            } else {
+              for (const exportedNode of self.getAllExportedNodes(sourceFile)) {
+                addAllSymbolsToScope(exportedNode, variableScope, typeScope, moduleScope, true);
+              }
+            }
+          }
+          break;
+        }
+
         case SyntaxKind.BoltSourceFile:
         case SyntaxKind.BoltModule:
         {
           for (const element of node.elements) {
-          this.addAllSymbolsInNode(element);
+            addAllSymbolsToScope(element, variableScope, typeScope, moduleScope);
           }
           break;
         }
 
         case SyntaxKind.BoltFunctionDeclaration:
         {
-        this.varResolver.addSymbol(emit(node.name), node);
+          const symbolName = emit(node.name);
+          const sym = self.lookupSymbolInScope(symbolName, variableScope, SymbolKind.Variable)
+          if (sym !== null) {
+            if (!allowDuplicates) {
+              throw new Error(`Symbol '${name}' is already defined.`);
+            }
+            if (sym.declarations.indexOf(node) === -1) {
+              throw new Error(`Different symbols imported under the same name.`);
+            }
+          } else {
+            self.addSymbolToScope(symbolName, node, variableScope, SymbolKind.Variable);
+          }
           break;
         }
 
         case SyntaxKind.BoltRecordDeclaration:
         {
-        this.typeResolver.addSymbol(node.name.text, node);
+          const symbolName = emit(node.name);
+          const sym = self.lookupSymbolInScope(symbolName, typeScope, SymbolKind.Type)
+          if (sym !== null) {
+            if (!allowDuplicates) {
+              throw new Error(`Symbol '${name}' is already defined.`);
+            }
+            if (sym.declarations.indexOf(node) === -1) {
+              throw new Error(`Different symbols imported under the same name.`);
+            }
+          } else {
+            self.addSymbolToScope(node.name.text, node, typeScope, SymbolKind.Type);
+          }
+          break;
         }
 
       }
 
     }
 
+  }
+
+  private getAllExportedNodes(node: BoltSyntax): BoltSyntax[] {
+
+    const nodes: BoltSyntax[] = [];
+    visit(node);
+    return nodes;
+
+    function visit(node: BoltSyntax) {
+      if (isBoltDeclaration(node) || isBoltTypeDeclaration(node)) {
+        if ((node.modifiers & BoltModifiers.IsPublic) > 0) {
+          nodes.push(node);
+        }
+      }
+      switch (node.kind) {
+        case SyntaxKind.BoltFunctionDeclaration:
+        case SyntaxKind.BoltRecordDeclaration:
+        case SyntaxKind.BoltTypeAliasDeclaration:
+          nodes.push(node);
+          break;
+        case SyntaxKind.BoltModule:
+        case SyntaxKind.BoltSourceFile:
+          for (const element of node.elements) {
+            visit(element);
+          }
+          break;
+      }
+    }
+
+  }
+
   private resolveReferenceExpression(node: BoltReferenceExpression): BoltDeclaration | null {
-    return this.varResolver.resolve(createDeclarationPath(node.name), node);
+    const symbolPath = nodeToSymbolPath(node.name)
+    return this.resolveSymbolPath(symbolPath, node, SymbolKind.Variable);
   }
 
   private resolveTypeReferenceExpression(node: BoltReferenceTypeExpression): BoltTypeDeclaration | null {
-    return this.typeResolver.resolve(createDeclarationPath(node.name), node);
+    const symbolPath = nodeToSymbolPath(node.name);
+    const scope = this.getScopeForNode(node, SymbolKind.Type);
+    return this.resolveSymbolPath(symbolPath, scope, SymbolKind.Type);
+  }
+
+  public addSymbol(name: string, node: BoltSyntax, kind: SymbolKind): void {
+    const scope = this.getScopeSurroundingNode(node, kind);
+    this.addSymbolToScope(name, node, scope, kind)
+  }
+
+  public addSymbolToScope(name: string, node: BoltSyntax, scope: ScopeInfo, symbolKindMask: SymbolKind): void {
+    verbose(`Adding symbol ${name} in scope #${scope.id}`);
+    const sym = { kind: symbolKindMask, declarations: [ node ] } as SymbolInfo;
+    for (const symbolKind of getAllSymbolKindsInMask(symbolKindMask)) {
+      this.symbols.set(`${symbolKind}:${name}:${scope.id}`, sym);
+    }
+  }
+
+  public getParentScope(scope: ScopeInfo, kind: SymbolKind): ScopeInfo | null {
+
+    // We might have already calculcated this scope's parent scope before;;
+    if (scope.parentScope !== undefined) {
+      return scope.parentScope;
+    }
+
+    if (isSyntax(scope.declaration)) {
+
+      // Edge case where there are no parent nodes left to traverse
+      if (scope.declaration.kind === SyntaxKind.BoltSourceFile) {
+        const pkg = (scope.declaration as BoltSourceFile).package;
+        return {
+          id: pkg.id,
+          declaration: pkg,
+        } as ScopeInfo;
+      }
+
+      return this.getScopeForNode(scope.declaration.parentNode!, kind)
+    }
+
+    // If the declaration was not an AST node, it can only be a package
+    return null;
+  }
+
+  public getScopeSurroundingNode(node: Syntax, kind: SymbolKind): ScopeInfo {
+    assert(node.parentNode !== null);
+    return this.getScopeForNode(node.parentNode!, kind);
+  }
+
+  public getScopeForNode(node: BoltSyntax, kind: SymbolKind): ScopeInfo {
+
+    let currNode = node;
+
+    while (true) {
+
+      // We might have created a scope for this node before,
+      // or saved the relevant scope for efficiency.
+      if (node._scope !== undefined) {
+        return node._scope;
+      }
+
+      // When we've reached a node that introduces a new scope according
+      // to the rules of the SymbolKind, we may continue.
+      if (this.introducesNewScope(currNode.kind, kind)) {
+        break;
+      }
+
+      assert(currNode.parentNode !== null);
+      currNode = currNode.parentNode!;
+    }
+
+    return {
+      id: currNode.id,
+      declaration: currNode,
+    } as ScopeInfo;
+  }
+
+  private lookupSymbolInScope(name: string, scope: ScopeInfo, symbolKindMask: SymbolKind): SymbolInfo | null {
+    for (const symbolKind of getAllSymbolKindsInMask(symbolKindMask)) {
+      const key = `${symbolKind}:${name}:${scope.id}`;
+      if (this.symbols.has(key)) {
+        return this.symbols.get(key);
+      }
+    }
+    return null;
+  }
+
+  private findSymbolInScopeOf(name: string, scope: ScopeInfo, kind: SymbolKind): SymbolInfo | null {
+    while (true) {
+
+      // Attempt to look up the symbol in the scope that was either passed to this
+      // method or one of its parents. If we found one, we're done.
+      const sym = this.lookupSymbolInScope(name, scope, kind);
+      if (sym !== null) {
+        return sym;
+      }
+
+      const parentScope = this.getParentScope(scope, kind);
+
+      // Failing to find a parent scope means that none of the enclosing
+      // scopes had the given variable. If this is the case, jump to the
+      // error handling logic.
+      if (parentScope === null) {
+        break;
+      }
+
+      scope = parentScope;
+    }
+
+    return null;
+  }
+
+  public resolveSymbolPath(path: SymbolPath, scope: ScopeInfo, kind: SymbolKind): BoltSyntax | null {
+
+    if (path.hasParents()) {
+
+      if (path.isAbsolute) {
+
+        // TODO
+
+      } else {
+
+        // We will keep looping until we are at the topmost module of
+        // the package corresponding to `node`.
+        while (true) {
+
+          let shouldSearchParentScopes = false;
+          let currScope = scope;
+
+          // Go through each of the parent names in normal order, resolving to the module
+          // that declared the name, and mark when we failed to look up the inner module.
+          for (const name of path.getParents()) {
+            const sym = this.lookupSymbolInScope(name, currScope, SymbolKind.Module);
+            if (sym === null) {
+              shouldSearchParentScopes = true;
+              break;
+            }
+            if (sym.declarations[0].kind !== SyntaxKind.BoltModule) {
+              shouldSearchParentScopes = true;
+              break;
+            }
+            currScope = this.getScopeForNode(sym.declarations[0], SymbolKind.Module);
+          }
+
+          // If the previous loop did not fail, we are done.
+          if (!shouldSearchParentScopes) {
+            scope = currScope;
+            break;
+          }
+
+          // We continue the outer loop by getting the parent module, which should be
+          // equivalent to getting the parent module scope.
+          const parentScope = this.getParentScope(scope, SymbolKind.Module);
+          if (parentScope === null) {
+            return null;
+          }
+          scope = parentScope;
+        }
+
+      }
+
+    }
+
+    // Once we've handled any module path that might have been present,
+    // we resolve the actual symbol using a helper method.
+
+    const sym = this.findSymbolInScopeOf(path.name, scope, kind);
+
+    if (sym === null) {
+      return null;
+    }
+
+    return sym.declarations[0]!;
+  }
+
+  private introducesNewScope(nodeKind: SyntaxKind, symbolKind: SymbolKind) {
+    switch (symbolKind) {
+      case SymbolKind.Variable:
+        return nodeKind === SyntaxKind.BoltSourceFile
+            || nodeKind === SyntaxKind.BoltModule
+            || nodeKind === SyntaxKind.BoltFunctionDeclaration
+            || nodeKind === SyntaxKind.BoltBlockExpression;
+      case SymbolKind.Type:
+        return nodeKind === SyntaxKind.BoltModule
+            || nodeKind === SyntaxKind.BoltSourceFile;
+      case SymbolKind.Module:
+        return nodeKind === SyntaxKind.BoltModule
+            || nodeKind === SyntaxKind.BoltSourceFile;
+    }
   }
 
 }

src/common.ts

@@ -10,16 +10,37 @@ import {
   isBoltPunctuated,
   SourceFile,
   BoltSourceFile,
-  BoltSourceFileModifiers
+  BoltSourceFileModifiers,
+  isSourceFile
 } from "./ast";
 import { BOLT_SUPPORTED_LANGUAGES } from "./constants"
 import {emit} from "./emitter";
-import {FastStringMap, enumerate, escapeChar} from "./util";
+import {FastStringMap, enumerate, escapeChar, assert} from "./util";
 import {TextSpan, TextPos, TextFile} from "./text";
 import {Scanner} from "./scanner";
 
+export function getSourceFile(node: Syntax) {
+  while (true) {
+    if (isSourceFile(node)) {
+      return node
+    }
+    assert(node.parentNode !== null);
+    node = node.parentNode;
+  }
+}
+
+export function getPackage(node: Syntax) {
+  const sourceFile = getSourceFile(node);
+  assert(sourceFile.kind === SyntaxKind.BoltSourceFile);
+  return (sourceFile as BoltSourceFile).package;
+}
+
+let nextPackageId = 1;
+
 export class Package {
 
+  public id = nextPackageId++;
+
   constructor(
     public rootDir: string,
     public name: string | null,
@@ -328,37 +349,3 @@ export function describeKind(kind: SyntaxKind): string {
   }
 }
 
-export type DeclarationPath = unknown;
-
-type DeclarationPathInfo = {
-  modulePath: string[],
-  isAbsolute: boolean,
-  name: string
-};
-
-export function getModulePath(path: DeclarationPath): string[] {
-  return (path as DeclarationPathInfo).modulePath;
-}
-
-export function hasAbsoluteModulePath(path: DeclarationPath): boolean {
-  return (path as DeclarationPathInfo).modulePath.length > 0 
-      && (path as DeclarationPathInfo).isAbsolute;
-}
-
-export function hasRelativeModulePath(path: DeclarationPath): boolean {
-  return (path as DeclarationPathInfo).modulePath.length > 0
-     && !(path as DeclarationPathInfo).isAbsolute;
-}
-
-export function getSymbolNameOfDeclarationPath(path: DeclarationPath): string {
-  return (path as DeclarationPathInfo).name;
-}
-
-export function createDeclarationPath(node: BoltQualName): DeclarationPath {
-  const name = emit(node.name);
-  if (node.modulePath === null) {
-    return { modulePath: [], isAbsolute: false, name };
-  }
-  return { modulePath: node.modulePath.map(id => id.text), isAbsolute: false, name };
-}
-

src/diagnostics.ts

@@ -1,8 +1,9 @@
 
 import chalk from "chalk"
 import {Syntax} from "./ast";
-import {format, MapLike, FormatArg} from "./util";
+import {format, MapLike, FormatArg, countDigits} from "./util";
 
+export const E_FILE_NOT_FOUND = "A file named {filename} was not found.";
 export const E_FIELD_HAS_INVALID_VERSION_NUMBER = "Field '{name}' contains an invalid version nunmber."
 export const E_FIELD_MUST_BE_STRING = "Field '{name}' must be a string."
 export const E_FIELD_NOT_PRESENT = "Field '{name}' is not present."
@@ -22,13 +23,6 @@ export interface Diagnostic {
   node?: Syntax;
 }
 
-export function countDigits(num: number) {
-  if (num === 0) {
-    return 1
-  }
-  return Math.ceil(Math.log10(num+1))
-}
-
 function firstIndexOfNonEmpty(str: string) {
   let j = 0;
   for (; j < str.length; j++) {

src/frontend.ts

@@ -70,11 +70,7 @@ export class Frontend {
 
   constructor() {
     this.diagnostics = new DiagnosticPrinter();
-    this.checker = new TypeChecker(this.diagnostics);
-    this.evaluator = new Evaluator(this.checker);
     this.timing = new Timing();
-    this.container.bindSelf(this.evaluator);
-    this.container.bindSelf(this.checker);
   }
 
   @memoize
@@ -89,16 +85,25 @@ export class Frontend {
   }
 
   public typeCheck(program: Program) {
+    const checker = new TypeChecker(this.diagnostics, program);
     for (const sourceFile of program.getAllSourceFiles()) {
-      this.checker.registerSourceFile(sourceFile as BoltSourceFile);
+      checker.registerSourceFile(sourceFile as BoltSourceFile);
     }
     for (const sourceFile of program.getAllSourceFiles()) {
-      this.checker.checkSourceFile(sourceFile as BoltSourceFile);
+      checker.checkSourceFile(sourceFile as BoltSourceFile);
     }
   }
 
   public compile(program: Program, target: string) {
 
+    // FIXME type checker should be shared across multple different method invocations
+    const checker = new TypeChecker(this.diagnostics, program);
+
+    const container = new Container();
+
+    //container.bindSelf(evaluator);
+    container.bindSelf(checker);
+
     switch (target) {
 
       case "JS":

src/parser.ts

@@ -337,15 +337,14 @@ export class Parser {
 
     const t1 = tokens.get();
     assertToken(t1, SyntaxKind.BoltStringLiteral);
-    const filename = (t1 as BoltStringLiteral).value;
 
-    const symbols: BoltImportSymbol[] = [];
+    const symbols: BoltImportSymbol[] = null;
     const t2 = tokens.get();
     if (t2.kind === SyntaxKind.BoltParenthesized) {
       // TODO implement grammar and parsing logic for symbols
     }
 
-    const node = createBoltImportDirective(modifiers, filename, symbols);
+    const node = createBoltImportDirective(modifiers, t1 as BoltStringLiteral, symbols);
     setOrigNodeRange(node, t0, t1);
     return node;
   }

src/program.ts

@@ -1,32 +1,70 @@
 
-import { Package } from "./common"
+import * as path from "path"
-import { SourceFile } from "./ast"
+import { Package, getPackage } from "./common"
-import { FastStringMap } from "./util";
+import { SourceFile, Syntax } from "./ast"
+import { FastStringMap, assert, isInsideDirectory, stripExtensions } from "./util";
 
 export class Program {
 
-  private transformed = new FastStringMap<string, SourceFile>();
+  private packagesByName = new FastStringMap<string, Package>();
+
+  private sourceFilesByFilePath = new FastStringMap<string, SourceFile>();
 
   constructor(
     pkgs: Package[]
   ) {
     for (const pkg of pkgs) {
       for (const sourceFile of pkg.sourceFiles) {
-        this.transformed.set(sourceFile.span!.file.fullPath, sourceFile);
+        this.sourceFilesByFilePath.set(stripExtensions(sourceFile.span!.file.fullPath), sourceFile);
       }
     }
   }
 
   public getAllSourceFiles() {
-    return this.transformed.values();
+    return this.sourceFilesByFilePath.values();
+  }
+
+  public getSourceFile(filepath: string): SourceFile | null {
+    assert(path.isAbsolute(filepath));
+    if (!this.sourceFilesByFilePath.has(filepath)) {
+      return null;
+    }
+    return this.sourceFilesByFilePath.get(filepath);
+  }
+
+  public getPackageNamed(name: string): Package {
+    return this.packagesByName.get(name);
+  }
+
+  public resolveToSourceFile(importPath: string, fromNode: Syntax): SourceFile | null {
+    let resolvedFilePath: string;
+    if (importPath.startsWith('.')) {
+      const pkg = getPackage(fromNode);
+      resolvedFilePath = path.join(pkg.rootDir, importPath.substring(2));
+      assert(isInsideDirectory(resolvedFilePath, pkg.rootDir));
+    } else {
+      const elements = importPath.split('/');
+      const pkg = this.getPackageNamed(elements[0]);
+      let filename: string;
+      if (elements.length === 1) {
+        filename = 'lib';
+      } else {
+        assert(elements.length > 0);
+        assert(!elements.slice(1).some(element => element.startsWith('.')));
+        filename = elements.slice(1).join(path.sep);
+      }
+      resolvedFilePath = path.join(pkg.rootDir, filename)
+      assert(isInsideDirectory(resolvedFilePath, pkg.rootDir));
+    }
+    return this.getSourceFile(resolvedFilePath);
   }
 
   public updateSourceFile(oldSourceFile: SourceFile, newSourceFile: SourceFile): void {
-    if (!this.transformed.has(oldSourceFile.span!.file.fullPath)) {
+    if (!this.sourceFilesByFilePath.has(oldSourceFile.span!.file.fullPath)) {
       throw new Error(`Could not update ${oldSourceFile.span!.file.origPath} because it was not found in this program.`);
     }
-    this.transformed.delete(oldSourceFile.span!.file.fullPath);
+    this.sourceFilesByFilePath.delete(oldSourceFile.span!.file.fullPath);
-    this.transformed.set(newSourceFile.span!.file.fullPath, newSourceFile);
+    this.sourceFilesByFilePath.set(newSourceFile.span!.file.fullPath, newSourceFile);
   }
 
 }

src/treegen/ast.dts.template

@@ -0,0 +1,25 @@
+
+import { Type } from "./types"
+import { ScopeInfo } from "./checker"
+import { Package } from "./common"
+import { TextSpan } from "./text"
+
+export function setParents(node: Syntax): void;
+
+export type SyntaxRange = [Syntax, Syntax];
+
+export function isSyntax(value: any): value is Syntax;
+
+interface SyntaxBase<K extends SyntaxKind> {
+  id: number;
+  _scope?: ScopeInfo;
+  kind: K;
+  parentNode: ParentTypesOf<K> | null;
+  span: TextSpan | null;
+  getChildNodes(): IterableIterator<ChildTypesOf<K>>,
+  findAllChildrenOfKind<K1 extends SyntaxKind>(kind: K1): IterableIterator<ResolveSyntaxKind<K1>>;
+}
+
+export type ResolveSyntaxKind<K extends SyntaxKind> = Extract<Syntax, { kind: K }>;
+
+

src/treegen/index.ts

@@ -98,12 +98,7 @@ export function generateAST(decls: Declaration[]) {
 
   // Write corresponding TypeScript declarations
 
-
+  dtsFile.write(fs.readFileSync(path.join(PACKAGE_ROOT, 'src', 'treegen', 'ast.dts.template'), 'utf8'));
-  // FIXME These imports are specific to our project and should somehow
-  //       form part of the user specification.
-  dtsFile.write('\nimport { Package } from "./common"\n\n');
-
-  dtsFile.write('export function isSyntax(value: any): value is Syntax;\n\n');
 
   dtsFile.write(`\nexport const enum SyntaxKind {\n`);
   for (const decl of leafNodes) {
@@ -111,27 +106,6 @@ export function generateAST(decls: Declaration[]) {
   }
   dtsFile.write(`}\n\n`);
 
-  dtsFile.write(`
-
-import { TextSpan } from "./text"
-
-export function setParents(node: Syntax): void;
-
-export type SyntaxRange = [Syntax, Syntax];
-
-interface SyntaxBase<K extends SyntaxKind> {
-  id: number;
-  kind: K;
-  parentNode: ParentTypesOf<K> | null;
-  span: TextSpan | null;
-  getChildNodes(): IterableIterator<ChildTypesOf<K>>,
-  findAllChildrenOfKind<K1 extends SyntaxKind>(kind: K1): IterableIterator<ResolveSyntaxKind<K1>>;
-}
-
-export type ResolveSyntaxKind<K extends SyntaxKind> = Extract<Syntax, { kind: K }>;
-
-`);
-
   for (const decl of decls) {
     if (decl.type === 'NodeDeclaration') {
       if (isLeafNode(decl.name)) {

src/util.ts

@@ -14,6 +14,18 @@ export interface JsonArray extends Array<Json> {  };
 export interface JsonObject { [key: string]: Json }
 export type Json = null | string | boolean | number | JsonArray | JsonObject;
 
+export function isInsideDirectory(filepath: string, rootDir: string): boolean {
+  const relPath = path.relative(rootDir, filepath)
+  return !relPath.startsWith('..');
+}
+
+export function stripExtensions(filepath: string) {
+  const i = filepath.indexOf('.')
+  return i !== -1
+    ? filepath.substring(0, i)
+    : filepath;
+}
+
 export function isString(value: any): boolean {
   return typeof value === 'string';
 }
@@ -22,6 +34,13 @@ export function hasOwnProperty<T extends object, K extends PropertyKey>(obj: T,
   return Object.prototype.hasOwnProperty.call(obj, key);
 }
 
+export function countDigits(x: number, base: number = 10) {
+  if (x === 0) {
+    return 1
+  }
+  return Math.ceil(Math.log(x+1) / Math.log(base))
+}
+
 export function uniq<T>(elements: T[]): T[] {
   const out: T[] = [];
   const visited = new Set<T>();