error recovery!

src/loader.ts

@@ -1,27 +1,41 @@
-import { DepCrate } from "./ast";
+import { CrateId, DepCrate } from "./ast";
 import { CrateLoader, GlobalContext } from "./context";
-import { CompilerError, LoadedFile, Span, withErrorPrinter } from "./error";
+import { CompilerError, ErrorEmitted, LoadedFile, Span } from "./error";
 import fs from "fs";
 import path from "path";
 import { tokenize } from "./lexer";
 import { ParseState, parse } from "./parser";
 import { resolve } from "./resolve";
 import { typeck } from "./typeck";
+import { ComplexMap } from "./utils";
+
+export type LoadResult<T> =
+  | {
+      ok: true;
+      value: T;
+    }
+  | {
+      ok: false;
+      err: CompilerError;
+    };
 
 export function loadModuleFile(
   relativeTo: string,
   moduleName: string,
   span: Span,
-): LoadedFile {
+): LoadResult<LoadedFile> {
   let searchDir: string;
   if (relativeTo.endsWith(".mod.nil")) {
     // x/uwu.mod.nil searches in x/
     searchDir = path.dirname(relativeTo);
   } else if (relativeTo.endsWith(".nil")) {
-    throw new CompilerError(
-      `.nil files cannot have submodules. use .mod.nil in a subdirectory`,
-      span,
-    );
+    return {
+      ok: false,
+      err: new CompilerError(
+        `.nil files cannot have submodules. use .mod.nil in a subdirectory`,
+        span,
+      ),
+    };
   } else {
     searchDir = relativeTo;
   }
@@ -41,13 +55,34 @@ export function loadModuleFile(
   });
 
   if (content === undefined || filePath === undefined) {
-    throw new CompilerError(
-      `failed to load ${moduleName}, could not find ${options.join(" or ")}`,
-      span,
-    );
+    return {
+      ok: false,
+      err: new CompilerError(
+        `failed to load ${moduleName}, could not find ${options.join(" or ")}`,
+        span,
+      ),
+    };
   }
 
-  return { content, path: filePath };
+  return { ok: true, value: { content, path: filePath } };
+}
+
+function dummyErrorCrate(
+  id: CrateId,
+  packageName: string,
+  emitted: ErrorEmitted,
+): DepCrate {
+  return {
+    id,
+    packageName,
+    rootItems: [],
+    itemsById: new ComplexMap(),
+    rootFile: { content: "<dummy>" },
+    fatalError: emitted,
+    typeckResults: {
+      main: undefined,
+    },
+  };
 }
 
 export const loadCrate: CrateLoader = (
@@ -65,27 +100,27 @@ export const loadCrate: CrateLoader = (
     return existing;
   }
 
-  return withErrorPrinter(
-    (): DepCrate => {
-      const file = loadModuleFile(".", name, span);
+  const crateId = gcx.crateId.next();
 
-      const crateId = gcx.crateId.next();
+  const file = loadModuleFile(".", name, span);
+  if (!file.ok) {
+    return dummyErrorCrate(crateId, name, gcx.error.emit(file.err));
+  }
 
-      const tokens = tokenize(file);
-      const parseState: ParseState = { tokens, file };
-      const ast = parse(name, parseState, crateId);
-      const resolved = resolve(gcx, ast);
+  const tokens = tokenize(gcx.error, file.value);
+  if (!tokens.ok) {
+    return dummyErrorCrate(crateId, name, tokens.err);
+  }
+  const parseState: ParseState = {
+    tokens: tokens.tokens,
+    file: file.value,
+    gcx,
+  };
+  const ast = parse(name, parseState, crateId);
+  const resolved = resolve(gcx, ast);
 
-      const typecked = typeck(gcx, resolved);
+  const typecked = typeck(gcx, resolved);
 
-      gcx.finalizedCrates.push(typecked);
-      return typecked;
-    },
-    () => {
-      throw new CompilerError(
-        `failed to load crate ${name}: crate contains errors`,
-        span,
-      );
-    },
-  );
+  gcx.finalizedCrates.push(typecked);
+  return typecked;
 };