feat: add --no-check option (#6456)

This commit adds a "--no-check" option to following subcommands:
- "deno cache"
- "deno info"
- "deno run"
- "deno test"

The "--no-check" options allows to skip type checking step and instead 
directly transpiles TS sources to JS sources. 

This solution uses `ts.transpileModule()` API and is just an interim
solution before implementing it fully in Rust.

78 files changed, 567 insertions, 200 deletions

diff --git a/cli/flags.rs b/cli/flags.rs
index 4cacb01e4..eb98c6032 100644
--- a/cli/flags.rs
+++ b/cli/flags.rs
@@ -106,6 +106,7 @@ pub struct Flags {
   pub lock_write: bool,
   pub log_level: Option<Level>,
   pub net_allowlist: Vec<String>,
+  pub no_check: bool,
   pub no_prompts: bool,
   pub no_remote: bool,
   pub read_allowlist: Vec<PathBuf>,
@@ -453,6 +454,7 @@ fn eval_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
 fn info_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   ca_file_arg_parse(flags, matches);
   unstable_arg_parse(flags, matches);
+  no_check_arg_parse(flags, matches);
 
   flags.subcommand = DenoSubcommand::Info {
     file: matches.value_of("file").map(|f| f.to_string()),
@@ -464,6 +466,7 @@ fn cache_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   lock_args_parse(flags, matches);
   importmap_arg_parse(flags, matches);
   config_arg_parse(flags, matches);
+  no_check_arg_parse(flags, matches);
   no_remote_arg_parse(flags, matches);
   ca_file_arg_parse(flags, matches);
   unstable_arg_parse(flags, matches);
@@ -492,6 +495,7 @@ fn run_test_args_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   importmap_arg_parse(flags, matches);
   config_arg_parse(flags, matches);
   v8_flags_arg_parse(flags, matches);
+  no_check_arg_parse(flags, matches);
   no_remote_arg_parse(flags, matches);
   permission_args_parse(flags, matches);
   ca_file_arg_parse(flags, matches);
@@ -818,6 +822,7 @@ TypeScript compiler cache: Subdirectory containing TS compiler output.",
     )
     .arg(Arg::with_name("file").takes_value(true).required(false))
     .arg(ca_file_arg())
+    .arg(no_check_arg())
     .arg(unstable_arg())
 }
 
@@ -829,6 +834,7 @@ fn cache_subcommand<'a, 'b>() -> App<'a, 'b> {
     .arg(importmap_arg())
     .arg(unstable_arg())
     .arg(config_arg())
+    .arg(no_check_arg())
     .arg(no_remote_arg())
     .arg(
       Arg::with_name("file")
@@ -1040,6 +1046,7 @@ fn run_test_args<'a, 'b>(app: App<'a, 'b>) -> App<'a, 'b> {
     .arg(config_arg())
     .arg(lock_arg())
     .arg(lock_write_arg())
+    .arg(no_check_arg())
     .arg(no_remote_arg())
     .arg(v8_flags_arg())
     .arg(ca_file_arg())
@@ -1314,6 +1321,18 @@ fn v8_flags_arg_parse(flags: &mut Flags, matches: &ArgMatches) {
   }
 }
 
+fn no_check_arg<'a, 'b>() -> Arg<'a, 'b> {
+  Arg::with_name("no-check")
+    .long("no-check")
+    .help("Skip type checking modules")
+}
+
+fn no_check_arg_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
+  if matches.is_present("no-check") {
+    flags.no_check = true;
+  }
+}
+
 fn no_remote_arg<'a, 'b>() -> Arg<'a, 'b> {
   Arg::with_name("no-remote")
     .long("no-remote")
@@ -2442,6 +2461,22 @@ mod tests {
   */
 
   #[test]
+  fn no_check() {
+    let r =
+      flags_from_vec_safe(svec!["deno", "run", "--no-check", "script.ts"]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Run {
+          script: "script.ts".to_string(),
+        },
+        no_check: true,
+        ..Flags::default()
+      }
+    );
+  }
+
+  #[test]
   fn no_remote() {
     let r =
       flags_from_vec_safe(svec!["deno", "run", "--no-remote", "script.ts"]);
diff --git a/cli/global_state.rs b/cli/global_state.rs
index cd04d03e6..e9988f4b5 100644
--- a/cli/global_state.rs
+++ b/cli/global_state.rs
@@ -170,17 +170,24 @@ impl GlobalState {
     let allow_js = should_allow_js(&module_graph_files);
 
     if should_compile {
-      self
-        .ts_compiler
-        .compile(
-          self.clone(),
-          &out,
-          target_lib,
-          permissions,
-          module_graph,
-          allow_js,
-        )
-        .await?;
+      if self.flags.no_check {
+        self
+          .ts_compiler
+          .transpile(self.clone(), permissions, module_graph)
+          .await?;
+      } else {
+        self
+          .ts_compiler
+          .compile(
+            self.clone(),
+            &out,
+            target_lib,
+            permissions,
+            module_graph,
+            allow_js,
+          )
+          .await?;
+      }
     }
 
     if let Some(ref lockfile) = self.lockfile {
diff --git a/cli/js/buffer.ts b/cli/js/buffer.ts
index 6a5105908..5c304c127 100644
--- a/cli/js/buffer.ts
+++ b/cli/js/buffer.ts
@@ -4,7 +4,7 @@
 // Copyright 2009 The Go Authors. All rights reserved. BSD license.
 // https://github.com/golang/go/blob/master/LICENSE
 
-import { Reader, Writer, ReaderSync, WriterSync } from "./io.ts";
+import type { Reader, Writer, ReaderSync, WriterSync } from "./io.ts";
 import { assert } from "./util.ts";
 
 // MIN_READ is the minimum ArrayBuffer size passed to a read call by
diff --git a/cli/js/compiler.ts b/cli/js/compiler.ts
index 500716a64..fc75a7c10 100644
--- a/cli/js/compiler.ts
+++ b/cli/js/compiler.ts
@@ -14,10 +14,10 @@
 import "./ts_global.d.ts";
 
 import { bold, cyan, yellow } from "./colors.ts";
-import { CompilerOptions } from "./compiler_options.ts";
-import { Diagnostic, DiagnosticItem } from "./diagnostics.ts";
+import type { CompilerOptions } from "./compiler_options.ts";
+import type { Diagnostic, DiagnosticItem } from "./diagnostics.ts";
 import { fromTypeScriptDiagnostic } from "./diagnostics_util.ts";
-import { TranspileOnlyResult } from "./ops/runtime_compiler.ts";
+import type { TranspileOnlyResult } from "./ops/runtime_compiler.ts";
 import { bootstrapWorkerRuntime } from "./runtime_worker.ts";
 import { assert, log, notImplemented } from "./util.ts";
 import { core } from "./core.ts";
@@ -47,6 +47,8 @@ const TS_BUILD_INFO = "cache:///tsbuildinfo.json";
 // TODO(Bartlomieju): this check should be done in Rust
 const IGNORED_COMPILER_OPTIONS: readonly string[] = [
   "allowSyntheticDefaultImports",
+  "allowUmdGlobalAccess",
+  "assumeChangesOnlyAffectDirectDependencies",
   "baseUrl",
   "build",
   "composite",
@@ -60,13 +62,13 @@ const IGNORED_COMPILER_OPTIONS: readonly string[] = [
   "esModuleInterop",
   "extendedDiagnostics",
   "forceConsistentCasingInFileNames",
+  "generateCpuProfile",
   "help",
   "importHelpers",
   "incremental",
   "inlineSourceMap",
   "inlineSources",
   "init",
-  "isolatedModules",
   "listEmittedFiles",
   "listFiles",
   "mapRoot",
@@ -139,10 +141,18 @@ const DEFAULT_COMPILE_OPTIONS: ts.CompilerOptions = {
   jsx: ts.JsxEmit.React,
   module: ts.ModuleKind.ESNext,
   outDir: OUT_DIR,
-  resolveJsonModule: true,
   sourceMap: true,
   strict: true,
-  stripComments: true,
+  removeComments: true,
+  target: ts.ScriptTarget.ESNext,
+};
+
+const DEFAULT_TRANSPILE_OPTIONS: ts.CompilerOptions = {
+  esModuleInterop: true,
+  inlineSourceMap: true,
+  jsx: ts.JsxEmit.React,
+  module: ts.ModuleKind.ESNext,
+  removeComments: true,
   target: ts.ScriptTarget.ESNext,
 };
 
@@ -172,16 +182,23 @@ interface CompilerHostOptions {
   incremental?: boolean;
 }
 
-interface IncrementalCompilerHostOptions extends CompilerHostOptions {
+type IncrementalCompilerHostOptions = Omit<
+  CompilerHostOptions,
+  "incremental"
+> & {
   rootNames?: string[];
   buildInfo?: string;
-}
+};
 
-interface ConfigureResponse {
+interface HostConfigureResponse {
   ignoredOptions?: string[];
   diagnostics?: ts.Diagnostic[];
 }
 
+interface ConfigureResponse extends HostConfigureResponse {
+  options: ts.CompilerOptions;
+}
+
 // Warning! The values in this enum are duplicated in `cli/msg.rs`
 // Update carefully!
 enum MediaType {
@@ -238,6 +255,37 @@ const SOURCE_FILE_CACHE: Map<string, SourceFile> = new Map();
  */
 const RESOLVED_SPECIFIER_CACHE: Map<string, Map<string, string>> = new Map();
 
+function configure(
+  defaultOptions: ts.CompilerOptions,
+  source: string,
+  path: string,
+  cwd: string
+): ConfigureResponse {
+  const { config, error } = ts.parseConfigFileTextToJson(path, source);
+  if (error) {
+    return { diagnostics: [error], options: defaultOptions };
+  }
+  const { options, errors } = ts.convertCompilerOptionsFromJson(
+    config.compilerOptions,
+    cwd
+  );
+  const ignoredOptions: string[] = [];
+  for (const key of Object.keys(options)) {
+    if (
+      IGNORED_COMPILER_OPTIONS.includes(key) &&
+      (!(key in defaultOptions) || options[key] !== defaultOptions[key])
+    ) {
+      ignoredOptions.push(key);
+      delete options[key];
+    }
+  }
+  return {
+    options: Object.assign({}, defaultOptions, options),
+    ignoredOptions: ignoredOptions.length ? ignoredOptions : undefined,
+    diagnostics: errors.length ? errors : undefined,
+  };
+}
+
 class SourceFile {
   extension!: ts.Extension;
   filename!: string;
@@ -314,7 +362,7 @@ function getAssetInternal(filename: string): SourceFile {
 }
 
 class Host implements ts.CompilerHost {
-  protected _options = DEFAULT_COMPILE_OPTIONS;
+  #options = DEFAULT_COMPILE_OPTIONS;
   readonly #target: CompilerHostTarget;
   readonly #writeFile: WriteFileCallback;
   /* Deno specific APIs */
@@ -330,12 +378,12 @@ class Host implements ts.CompilerHost {
     this.#writeFile = writeFile;
     if (bundle) {
       // options we need to change when we are generating a bundle
-      Object.assign(this._options, DEFAULT_BUNDLER_OPTIONS);
+      Object.assign(this.#options, DEFAULT_BUNDLER_OPTIONS);
     } else if (incremental) {
-      Object.assign(this._options, DEFAULT_INCREMENTAL_COMPILE_OPTIONS);
+      Object.assign(this.#options, DEFAULT_INCREMENTAL_COMPILE_OPTIONS);
     }
     if (unstable) {
-      this._options.lib = [
+      this.#options.lib = [
         target === CompilerHostTarget.Worker
           ? "lib.deno.worker.d.ts"
           : "lib.deno.window.d.ts",
@@ -345,47 +393,28 @@ class Host implements ts.CompilerHost {
   }
 
   get options(): ts.CompilerOptions {
-    return this._options;
+    return this.#options;
   }
 
   configure(
     cwd: string,
     path: string,
     configurationText: string
-  ): ConfigureResponse {
+  ): HostConfigureResponse {
     log("compiler::host.configure", path);
-    assert(configurationText);
-    const { config, error } = ts.parseConfigFileTextToJson(
+    const { options, ...result } = configure(
+      this.#options,
+      configurationText,
       path,
-      configurationText
-    );
-    if (error) {
-      return { diagnostics: [error] };
-    }
-    const { options, errors } = ts.convertCompilerOptionsFromJson(
-      config.compilerOptions,
       cwd
     );
-    const ignoredOptions: string[] = [];
-    for (const key of Object.keys(options)) {
-      if (
-        IGNORED_COMPILER_OPTIONS.includes(key) &&
-        (!(key in this._options) || options[key] !== this._options[key])
-      ) {
-        ignoredOptions.push(key);
-        delete options[key];
-      }
-    }
-    Object.assign(this._options, options);
-    return {
-      ignoredOptions: ignoredOptions.length ? ignoredOptions : undefined,
-      diagnostics: errors.length ? errors : undefined,
-    };
+    this.#options = options;
+    return result;
   }
 
   mergeOptions(...options: ts.CompilerOptions[]): ts.CompilerOptions {
-    Object.assign(this._options, ...options);
-    return Object.assign({}, this._options);
+    Object.assign(this.#options, ...options);
+    return Object.assign({}, this.#options);
   }
 
   /* TypeScript CompilerHost APIs */
@@ -400,7 +429,7 @@ class Host implements ts.CompilerHost {
 
   getCompilationSettings(): ts.CompilerOptions {
     log("compiler::host.getCompilationSettings()");
-    return this._options;
+    return this.#options;
   }
 
   getCurrentDirectory(): string {
@@ -522,7 +551,7 @@ class IncrementalCompileHost extends Host {
   readonly #buildInfo?: string;
 
   constructor(options: IncrementalCompilerHostOptions) {
-    super(options);
+    super({ ...options, incremental: true });
     const { buildInfo } = options;
     if (buildInfo) {
       this.#buildInfo = buildInfo;
@@ -735,10 +764,11 @@ interface BundleWriteFileState {
 // Update carefully!
 enum CompilerRequestType {
   Compile = 0,
-  Bundle = 1,
-  RuntimeCompile = 2,
-  RuntimeBundle = 3,
-  RuntimeTranspile = 4,
+  Transpile = 1,
+  Bundle = 2,
+  RuntimeCompile = 3,
+  RuntimeBundle = 4,
+  RuntimeTranspile = 5,
 }
 
 function createBundleWriteFile(state: BundleWriteFileState): WriteFileCallback {
@@ -943,16 +973,29 @@ function performanceStart(): void {
   ts.performance.enable();
 }
 
-function performanceProgram(program: ts.Program | ts.BuilderProgram): void {
-  if ("getProgram" in program) {
-    program = program.getProgram();
+function performanceProgram({
+  program,
+  fileCount,
+}: {
+  program?: ts.Program | ts.BuilderProgram;
+  fileCount?: number;
+}): void {
+  if (program) {
+    if ("getProgram" in program) {
+      program = program.getProgram();
+    }
+    stats.push({ key: "Files", value: program.getSourceFiles().length });
+    stats.push({ key: "Nodes", value: program.getNodeCount() });
+    stats.push({ key: "Identifiers", value: program.getIdentifierCount() });
+    stats.push({ key: "Symbols", value: program.getSymbolCount() });
+    stats.push({ key: "Types", value: program.getTypeCount() });
+    stats.push({
+      key: "Instantiations",
+      value: program.getInstantiationCount(),
+    });
+  } else if (fileCount != null) {
+    stats.push({ key: "Files", value: fileCount });
   }
-  stats.push({ key: "Files", value: program.getSourceFiles().length });
-  stats.push({ key: "Nodes", value: program.getNodeCount() });
-  stats.push({ key: "Identifiers", value: program.getIdentifierCount() });
-  stats.push({ key: "Symbols", value: program.getSymbolCount() });
-  stats.push({ key: "Types", value: program.getTypeCount() });
-  stats.push({ key: "Instantiations", value: program.getInstantiationCount() });
   const programTime = ts.performance.getDuration("Program");
   const bindTime = ts.performance.getDuration("Bind");
   const checkTime = ts.performance.getDuration("Check");
@@ -976,7 +1019,7 @@ function performanceEnd(): Stats {
 
 // TODO(Bartlomieju): this check should be done in Rust; there should be no
 function processConfigureResponse(
-  configResult: ConfigureResponse,
+  configResult: HostConfigureResponse,
   configPath: string
 ): ts.Diagnostic[] | undefined {
   const { ignoredOptions, diagnostics } = configResult;
@@ -1209,6 +1252,20 @@ interface CompileRequest {
   buildInfo?: string;
 }
 
+interface TranspileRequest {
+  type: CompilerRequestType.Transpile;
+  config?: string;
+  configPath?: string;
+  cwd?: string;
+  performance: boolean;
+  sourceFiles: TranspileSourceFile[];
+}
+
+interface TranspileSourceFile {
+  sourceCode: string;
+  fileName: string;
+}
+
 /** Used when "deno bundle" is invoked */
 interface BundleRequest {
   type: CompilerRequestType.Bundle;
@@ -1252,6 +1309,7 @@ interface RuntimeTranspileRequest {
 
 type CompilerRequest =
   | CompileRequest
+  | TranspileRequest
   | BundleRequest
   | RuntimeCompileRequest
   | RuntimeBundleRequest
@@ -1264,6 +1322,12 @@ interface CompileResponse {
   stats?: Stats;
 }
 
+interface TranspileResponse {
+  emitMap: Record<string, EmittedSource>;
+  diagnostics: Diagnostic;
+  stats?: Stats;
+}
+
 interface BundleResponse {
   bundleOutput?: string;
   diagnostics: Diagnostic;
@@ -1310,7 +1374,6 @@ function compile({
     bundle: false,
     target,
     unstable,
-    incremental: true,
     writeFile: createCompileWriteFile(state),
     rootNames,
     buildInfo,
@@ -1364,7 +1427,7 @@ function compile({
       // without casting.
       diagnostics = emitResult.diagnostics;
     }
-    performanceProgram(program);
+    performanceProgram({ program });
   }
 
   log("<<< compile end", { rootNames, type: CompilerRequestType[type] });
@@ -1378,21 +1441,81 @@ function compile({
   };
 }
 
+function transpile({
+  config: configText,
+  configPath,
+  cwd,
+  performance,
+  sourceFiles,
+}: TranspileRequest): TranspileResponse {
+  if (performance) {
+    performanceStart();
+  }
+  log(">>> transpile start");
+  let compilerOptions: ts.CompilerOptions;
+  if (configText && configPath && cwd) {
+    const { options, ...response } = configure(
+      DEFAULT_TRANSPILE_OPTIONS,
+      configText,
+      configPath,
+      cwd
+    );
+    const diagnostics = processConfigureResponse(response, configPath);
+    if (diagnostics && diagnostics.length) {
+      return {
+        diagnostics: fromTypeScriptDiagnostic(diagnostics),
+        emitMap: {},
+      };
+    }
+    compilerOptions = options;
+  } else {
+    compilerOptions = Object.assign({}, DEFAULT_TRANSPILE_OPTIONS);
+  }
+  const emitMap: Record<string, EmittedSource> = {};
+  let diagnostics: ts.Diagnostic[] = [];
+  for (const { sourceCode, fileName } of sourceFiles) {
+    const {
+      outputText,
+      sourceMapText,
+      diagnostics: diags,
+    } = ts.transpileModule(sourceCode, {
+      fileName,
+      compilerOptions,
+      reportDiagnostics: true,
+    });
+    if (diags) {
+      diagnostics = diagnostics.concat(...diags);
+    }
+    emitMap[`${fileName}.js`] = { filename: fileName, contents: outputText };
+    // currently we inline source maps, but this is good logic to have if this
+    // ever changes
+    if (sourceMapText) {
+      emitMap[`${fileName}.map`] = {
+        filename: fileName,
+        contents: sourceMapText,
+      };
+    }
+  }
+  performanceProgram({ fileCount: sourceFiles.length });
+  const stats = performance ? performanceEnd() : undefined;
+  log("<<< transpile end");
+  return { diagnostics: fromTypeScriptDiagnostic(diagnostics), emitMap, stats };
+}
+
 function bundle({
-  type,
   config,
   configPath,
   rootNames,
   target,
   unstable,
-  performance,
   cwd,
   sourceFileMap,
+  type,
 }: BundleRequest): BundleResponse {
   if (performance) {
     performanceStart();
   }
-  log(">>> start start", {
+  log(">>> bundle start", {
     rootNames,
     type: CompilerRequestType[type],
   });
@@ -1447,7 +1570,7 @@ function bundle({
       diagnostics = emitResult.diagnostics;
     }
     if (performance) {
-      performanceProgram(program);
+      performanceProgram({ program });
     }
   }
 
@@ -1655,6 +1778,11 @@ async function tsCompilerOnMessage({
       globalThis.postMessage(result);
       break;
     }
+    case CompilerRequestType.Transpile: {
+      const result = transpile(request);
+      globalThis.postMessage(result);
+      break;
+    }
     case CompilerRequestType.Bundle: {
       const result = bundle(request);
       globalThis.postMessage(result);
diff --git a/cli/js/compiler_api.ts b/cli/js/compiler_api.ts
index 0f4aec887..8a50e0b3d 100644
--- a/cli/js/compiler_api.ts
+++ b/cli/js/compiler_api.ts
@@ -3,11 +3,11 @@
 // This file contains the runtime APIs which will dispatch work to the internal
 // compiler within Deno.
 
-import { DiagnosticItem } from "./diagnostics.ts";
+import type { DiagnosticItem } from "./diagnostics.ts";
 import * as util from "./util.ts";
 import * as runtimeCompilerOps from "./ops/runtime_compiler.ts";
-import { TranspileOnlyResult } from "./ops/runtime_compiler.ts";
-import { CompilerOptions } from "./compiler_options.ts";
+import type { TranspileOnlyResult } from "./ops/runtime_compiler.ts";
+import type { CompilerOptions } from "./compiler_options.ts";
 
 function checkRelative(specifier: string): string {
   return specifier.match(/^([\.\/\\]|https?:\/{2}|file:\/{2})/)
diff --git a/cli/js/deno.ts b/cli/js/deno.ts
index 6570042af..878df8fb4 100644
--- a/cli/js/deno.ts
+++ b/cli/js/deno.ts
@@ -27,16 +27,15 @@ export {
   stderr,
   seek,
   seekSync,
-  OpenOptions,
 } from "./files.ts";
+export type { OpenOptions } from "./files.ts";
 export { read, readSync, write, writeSync } from "./ops/io.ts";
-export { FsEvent, watchFs } from "./ops/fs_events.ts";
+export { watchFs } from "./ops/fs_events.ts";
+export type { FsEvent } from "./ops/fs_events.ts";
 export { internalSymbol as internal } from "./internals.ts";
-export {
-  copy,
-  iter,
-  iterSync,
-  SeekMode,
+export { copy, iter, iterSync } from "./io.ts";
+export { SeekMode } from "./io.ts";
+export type {
   Reader,
   ReaderSync,
   Writer,
@@ -49,30 +48,39 @@ export {
   makeTempDir,
   makeTempFileSync,
   makeTempFile,
-  MakeTempOptions,
 } from "./ops/fs/make_temp.ts";
-export { metrics, Metrics } from "./ops/runtime.ts";
-export { mkdirSync, mkdir, MkdirOptions } from "./ops/fs/mkdir.ts";
-export { connect, listen, Listener, Conn } from "./net.ts";
+export type { MakeTempOptions } from "./ops/fs/make_temp.ts";
+export { metrics } from "./ops/runtime.ts";
+export type { Metrics } from "./ops/runtime.ts";
+export { mkdirSync, mkdir } from "./ops/fs/mkdir.ts";
+export type { MkdirOptions } from "./ops/fs/mkdir.ts";
+export { connect, listen } from "./net.ts";
+export type { Listener, Conn } from "./net.ts";
 export { env, exit, execPath } from "./ops/os.ts";
-export { run, RunOptions, Process, ProcessStatus } from "./process.ts";
-export { DirEntry, readDirSync, readDir } from "./ops/fs/read_dir.ts";
+export { Process, run } from "./process.ts";
+export type { RunOptions, ProcessStatus } from "./process.ts";
+export { readDirSync, readDir } from "./ops/fs/read_dir.ts";
+export type { DirEntry } from "./ops/fs/read_dir.ts";
 export { readFileSync, readFile } from "./read_file.ts";
 export { readTextFileSync, readTextFile } from "./read_text_file.ts";
 export { readLinkSync, readLink } from "./ops/fs/read_link.ts";
 export { realPathSync, realPath } from "./ops/fs/real_path.ts";
-export { removeSync, remove, RemoveOptions } from "./ops/fs/remove.ts";
+export { removeSync, remove } from "./ops/fs/remove.ts";
+export type { RemoveOptions } from "./ops/fs/remove.ts";
 export { renameSync, rename } from "./ops/fs/rename.ts";
 export { resources, close } from "./ops/resources.ts";
-export { FileInfo, statSync, lstatSync, stat, lstat } from "./ops/fs/stat.ts";
+export { statSync, lstatSync, stat, lstat } from "./ops/fs/stat.ts";
+export type { FileInfo } from "./ops/fs/stat.ts";
 export { connectTls, listenTls } from "./tls.ts";
 export { truncateSync, truncate } from "./ops/fs/truncate.ts";
 export { isatty } from "./ops/tty.ts";
 export { version } from "./version.ts";
-export { writeFileSync, writeFile, WriteFileOptions } from "./write_file.ts";
+export { writeFileSync, writeFile } from "./write_file.ts";
+export type { WriteFileOptions } from "./write_file.ts";
 export { writeTextFileSync, writeTextFile } from "./write_text_file.ts";
 export const args: string[] = [];
-export { TestDefinition, test } from "./testing.ts";
+export { test } from "./testing.ts";
+export type { TestDefinition } from "./testing.ts";
 
 // These are internal Deno APIs.  We are marking them as internal so they do not
 // appear in the runtime type library.
diff --git a/cli/js/deno_unstable.ts b/cli/js/deno_unstable.ts
index e7a0510be..8744abba4 100644
--- a/cli/js/deno_unstable.ts
+++ b/cli/js/deno_unstable.ts
@@ -15,20 +15,16 @@ export { signal, signals, Signal, SignalStream } from "./signals.ts";
 export { setRaw } from "./ops/tty.ts";
 export { utimeSync, utime } from "./ops/fs/utime.ts";
 export { ftruncateSync, ftruncate } from "./ops/fs/truncate.ts";
-export { ShutdownMode, shutdown } from "./net.ts";
+export { shutdown, ShutdownMode } from "./net.ts";
 export { listen, listenDatagram, connect } from "./net_unstable.ts";
 export { startTls } from "./tls.ts";
 export { kill } from "./ops/process.ts";
-export {
-  permissions,
-  PermissionName,
-  PermissionState,
-  PermissionStatus,
-  Permissions,
-} from "./permissions.ts";
-export {
+export { permissions, Permissions } from "./permissions.ts";
+export { PermissionStatus } from "./permissions.ts";
+export type { PermissionName, PermissionState } from "./permissions.ts";
+export { DiagnosticCategory } from "./diagnostics.ts";
+export type {
   Diagnostic,
-  DiagnosticCategory,
   DiagnosticItem,
   DiagnosticMessageChain,
 } from "./diagnostics.ts";
diff --git a/cli/js/files.ts b/cli/js/files.ts
index 3dc48420d..3afcb4878 100644
--- a/cli/js/files.ts
+++ b/cli/js/files.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import {
+import type {
   Reader,
   Writer,
   Seeker,
@@ -19,7 +19,7 @@ import {
   openSync as opOpenSync,
   OpenOptions,
 } from "./ops/fs/open.ts";
-export { OpenOptions } from "./ops/fs/open.ts";
+export type { OpenOptions } from "./ops/fs/open.ts";
 
 export function openSync(
   path: string | URL,
diff --git a/cli/js/globals.ts b/cli/js/globals.ts
index 5746b224f..c73a2a6ab 100644
--- a/cli/js/globals.ts
+++ b/cli/js/globals.ts
@@ -7,7 +7,7 @@ import * as abortSignal from "./web/abort_signal.ts";
 import * as blob from "./web/blob.ts";
 import * as consoleTypes from "./web/console.ts";
 import * as csprng from "./ops/get_random_values.ts";
-import * as promiseTypes from "./web/promise.ts";
+import type * as promiseTypes from "./web/promise.ts";
 import * as customEvent from "./web/custom_event.ts";
 import * as domException from "./web/dom_exception.ts";
 import * as domFile from "./web/dom_file.ts";
diff --git a/cli/js/net.ts b/cli/js/net.ts
index e5e6af7bd..a4aad0254 100644
--- a/cli/js/net.ts
+++ b/cli/js/net.ts
@@ -1,12 +1,13 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { errors } from "./errors.ts";
-import { Reader, Writer, Closer } from "./io.ts";
+import type { Reader, Writer, Closer } from "./io.ts";
 import { read, write } from "./ops/io.ts";
 import { close } from "./ops/resources.ts";
 import * as netOps from "./ops/net.ts";
-import { Addr } from "./ops/net.ts";
-export { ShutdownMode, shutdown, NetAddr, UnixAddr } from "./ops/net.ts";
+import type { Addr } from "./ops/net.ts";
+export type { ShutdownMode, NetAddr, UnixAddr } from "./ops/net.ts";
+export { shutdown } from "./ops/net.ts";
 
 export interface DatagramConn extends AsyncIterable<[Uint8Array, Addr]> {
   receive(p?: Uint8Array): Promise<[Uint8Array, Addr]>;
diff --git a/cli/js/ops/errors.ts b/cli/js/ops/errors.ts
index c6c26b8ba..002ca699e 100644
--- a/cli/js/ops/errors.ts
+++ b/cli/js/ops/errors.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { DiagnosticItem } from "../diagnostics.ts";
+import type { DiagnosticItem } from "../diagnostics.ts";
 import { sendSync } from "./dispatch_json.ts";
 
 export function formatDiagnostics(items: DiagnosticItem[]): string {
diff --git a/cli/js/ops/fs/seek.ts b/cli/js/ops/fs/seek.ts
index 2e23e084b..8fd3964fd 100644
--- a/cli/js/ops/fs/seek.ts
+++ b/cli/js/ops/fs/seek.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { sendSync, sendAsync } from "../dispatch_json.ts";
-import { SeekMode } from "../../io.ts";
+import type { SeekMode } from "../../io.ts";
 
 export function seekSync(
   rid: number,
diff --git a/cli/js/ops/permissions.ts b/cli/js/ops/permissions.ts
index dfe8c4834..74b9ba0f0 100644
--- a/cli/js/ops/permissions.ts
+++ b/cli/js/ops/permissions.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { sendSync } from "./dispatch_json.ts";
-import { PermissionState } from "../permissions.ts";
+import type { PermissionState } from "../permissions.ts";
 
 interface PermissionRequest {
   name: string;
diff --git a/cli/js/ops/runtime_compiler.ts b/cli/js/ops/runtime_compiler.ts
index 5a89983ee..671585118 100644
--- a/cli/js/ops/runtime_compiler.ts
+++ b/cli/js/ops/runtime_compiler.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { sendAsync } from "./dispatch_json.ts";
-import { DiagnosticItem } from "../diagnostics.ts";
+import type { DiagnosticItem } from "../diagnostics.ts";
 
 interface CompileRequest {
   rootName: string;
diff --git a/cli/js/process.ts b/cli/js/process.ts
index 6f45081dc..ee32eac3d 100644
--- a/cli/js/process.ts
+++ b/cli/js/process.ts
@@ -2,7 +2,7 @@
 
 import { File } from "./files.ts";
 import { close } from "./ops/resources.ts";
-import { Closer, Reader, Writer } from "./io.ts";
+import type { Closer, Reader, Writer } from "./io.ts";
 import { readAll } from "./buffer.ts";
 import { kill, runStatus as runStatusOp, run as runOp } from "./ops/process.ts";
 
diff --git a/cli/js/web/body.ts b/cli/js/web/body.ts
index 3bcda0634..69aca459f 100644
--- a/cli/js/web/body.ts
+++ b/cli/js/web/body.ts
@@ -2,7 +2,7 @@
 
 import * as blob from "./blob.ts";
 import * as encoding from "./text_encoding.ts";
-import * as domTypes from "./dom_types.d.ts";
+import type * as domTypes from "./dom_types.d.ts";
 import { ReadableStreamImpl } from "./streams/readable_stream.ts";
 import { isReadableStreamDisturbed } from "./streams/internals.ts";
 import { Buffer } from "../buffer.ts";
diff --git a/cli/js/web/event.ts b/cli/js/web/event.ts
index b57c0f901..556d403a6 100644
--- a/cli/js/web/event.ts
+++ b/cli/js/web/event.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import * as domTypes from "./dom_types.d.ts";
+import type * as domTypes from "./dom_types.d.ts";
 import { defineEnumerableProps, requiredArguments } from "./util.ts";
 import { assert } from "../util.ts";
 
diff --git a/cli/js/web/event_target.ts b/cli/js/web/event_target.ts
index 1a560dfbe..6f6897425 100644
--- a/cli/js/web/event_target.ts
+++ b/cli/js/web/event_target.ts
@@ -6,7 +6,7 @@
 // and impossible logic branches based on what Deno currently supports.
 
 import { DOMExceptionImpl as DOMException } from "./dom_exception.ts";
-import * as domTypes from "./dom_types.d.ts";
+import type * as domTypes from "./dom_types.d.ts";
 import {
   EventImpl as Event,
   EventPath,
diff --git a/cli/js/web/fetch.ts b/cli/js/web/fetch.ts
index 33cf12069..543560c8d 100644
--- a/cli/js/web/fetch.ts
+++ b/cli/js/web/fetch.ts
@@ -2,12 +2,13 @@
 
 import { notImplemented } from "../util.ts";
 import { isTypedArray } from "./util.ts";
-import * as domTypes from "./dom_types.d.ts";
+import type * as domTypes from "./dom_types.d.ts";
 import { TextEncoder } from "./text_encoding.ts";
 import { DenoBlob, bytesSymbol as blobBytesSymbol } from "./blob.ts";
 import { read } from "../ops/io.ts";
 import { close } from "../ops/resources.ts";
-import { fetch as opFetch, FetchResponse } from "../ops/fetch.ts";
+import { fetch as opFetch } from "../ops/fetch.ts";
+import type { FetchResponse } from "../ops/fetch.ts";
 import * as Body from "./body.ts";
 import { getHeaderValueParams } from "./util.ts";
 import { ReadableStreamImpl } from "./streams/readable_stream.ts";
diff --git a/cli/js/web/request.ts b/cli/js/web/request.ts
index 7ea6a9ecd..f65b6a363 100644
--- a/cli/js/web/request.ts
+++ b/cli/js/web/request.ts
@@ -1,7 +1,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import * as body from "./body.ts";
-import * as domTypes from "./dom_types.d.ts";
+import type * as domTypes from "./dom_types.d.ts";
 import { ReadableStreamImpl } from "./streams/readable_stream.ts";
 
 function byteUpperCase(s: string): string {
diff --git a/cli/js/web/streams/internals.ts b/cli/js/web/streams/internals.ts
index 3fbfb7735..f6b20ccaf 100644
--- a/cli/js/web/streams/internals.ts
+++ b/cli/js/web/streams/internals.ts
@@ -12,7 +12,7 @@ import { ReadableStreamDefaultControllerImpl } from "./readable_stream_default_c
 import { ReadableStreamDefaultReaderImpl } from "./readable_stream_default_reader.ts";
 import { ReadableStreamImpl } from "./readable_stream.ts";
 import * as sym from "./symbols.ts";
-import { TransformStreamImpl } from "./transform_stream.ts";
+import type { TransformStreamImpl } from "./transform_stream.ts";
 import { TransformStreamDefaultControllerImpl } from "./transform_stream_default_controller.ts";
 import { WritableStreamDefaultControllerImpl } from "./writable_stream_default_controller.ts";
 import { WritableStreamDefaultWriterImpl } from "./writable_stream_default_writer.ts";
diff --git a/cli/js/web/streams/readable_byte_stream_controller.ts b/cli/js/web/streams/readable_byte_stream_controller.ts
index cbef64357..65409dc1e 100644
--- a/cli/js/web/streams/readable_byte_stream_controller.ts
+++ b/cli/js/web/streams/readable_byte_stream_controller.ts
@@ -20,7 +20,7 @@ import {
   readableStreamCreateReadResult,
   setFunctionName,
 } from "./internals.ts";
-import { ReadableStreamImpl } from "./readable_stream.ts";
+import type { ReadableStreamImpl } from "./readable_stream.ts";
 import * as sym from "./symbols.ts";
 import { assert } from "../../util.ts";
 import { customInspect } from "../console.ts";
diff --git a/cli/js/web/streams/readable_stream.ts b/cli/js/web/streams/readable_stream.ts
index 27a733d9d..3191c0859 100644
--- a/cli/js/web/streams/readable_stream.ts
+++ b/cli/js/web/streams/readable_stream.ts
@@ -19,9 +19,9 @@ import {
   setUpReadableStreamDefaultControllerFromUnderlyingSource,
   validateAndNormalizeHighWaterMark,
 } from "./internals.ts";
-import { ReadableByteStreamControllerImpl } from "./readable_byte_stream_controller.ts";
+import type { ReadableByteStreamControllerImpl } from "./readable_byte_stream_controller.ts";
 import { ReadableStreamAsyncIteratorPrototype } from "./readable_stream_async_iterator.ts";
-import { ReadableStreamDefaultControllerImpl } from "./readable_stream_default_controller.ts";
+import type { ReadableStreamDefaultControllerImpl } from "./readable_stream_default_controller.ts";
 import * as sym from "./symbols.ts";
 import { customInspect } from "../console.ts";
 import { AbortSignalImpl } from "../abort_signal.ts";
diff --git a/cli/js/web/streams/readable_stream_default_controller.ts b/cli/js/web/streams/readable_stream_default_controller.ts
index 0755e7765..47cb719c7 100644
--- a/cli/js/web/streams/readable_stream_default_controller.ts
+++ b/cli/js/web/streams/readable_stream_default_controller.ts
@@ -20,7 +20,7 @@ import {
   SizeAlgorithm,
   setFunctionName,
 } from "./internals.ts";
-import { ReadableStreamImpl } from "./readable_stream.ts";
+import type { ReadableStreamImpl } from "./readable_stream.ts";
 import * as sym from "./symbols.ts";
 import { customInspect } from "../console.ts";
 
diff --git a/cli/js/web/streams/readable_stream_default_reader.ts b/cli/js/web/streams/readable_stream_default_reader.ts
index a0d5901dc..01b679cd3 100644
--- a/cli/js/web/streams/readable_stream_default_reader.ts
+++ b/cli/js/web/streams/readable_stream_default_reader.ts
@@ -11,7 +11,7 @@ import {
   readableStreamReaderGenericRelease,
   setFunctionName,
 } from "./internals.ts";
-import { ReadableStreamImpl } from "./readable_stream.ts";
+import type { ReadableStreamImpl } from "./readable_stream.ts";
 import * as sym from "./symbols.ts";
 import { customInspect } from "../console.ts";
 
diff --git a/cli/js/web/streams/transform_stream.ts b/cli/js/web/streams/transform_stream.ts
index ac08fea3f..548a20b38 100644
--- a/cli/js/web/streams/transform_stream.ts
+++ b/cli/js/web/streams/transform_stream.ts
@@ -11,10 +11,10 @@ import {
   setUpTransformStreamDefaultControllerFromTransformer,
   validateAndNormalizeHighWaterMark,
 } from "./internals.ts";
-import { ReadableStreamImpl } from "./readable_stream.ts";
+import type { ReadableStreamImpl } from "./readable_stream.ts";
 import * as sym from "./symbols.ts";
-import { TransformStreamDefaultControllerImpl } from "./transform_stream_default_controller.ts";
-import { WritableStreamImpl } from "./writable_stream.ts";
+import type { TransformStreamDefaultControllerImpl } from "./transform_stream_default_controller.ts";
+import type { WritableStreamImpl } from "./writable_stream.ts";
 import { customInspect, inspect } from "../console.ts";
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
diff --git a/cli/js/web/streams/transform_stream_default_controller.ts b/cli/js/web/streams/transform_stream_default_controller.ts
index 2fc8d2160..78beaf879 100644
--- a/cli/js/web/streams/transform_stream_default_controller.ts
+++ b/cli/js/web/streams/transform_stream_default_controller.ts
@@ -10,9 +10,9 @@ import {
   transformStreamDefaultControllerError,
   transformStreamDefaultControllerTerminate,
 } from "./internals.ts";
-import { ReadableStreamDefaultControllerImpl } from "./readable_stream_default_controller.ts";
+import type { ReadableStreamDefaultControllerImpl } from "./readable_stream_default_controller.ts";
 import * as sym from "./symbols.ts";
-import { TransformStreamImpl } from "./transform_stream.ts";
+import type { TransformStreamImpl } from "./transform_stream.ts";
 import { customInspect } from "../console.ts";
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
diff --git a/cli/js/web/streams/writable_stream.ts b/cli/js/web/streams/writable_stream.ts
index 4bbf339da..8a31f512d 100644
--- a/cli/js/web/streams/writable_stream.ts
+++ b/cli/js/web/streams/writable_stream.ts
@@ -16,8 +16,8 @@ import {
   validateAndNormalizeHighWaterMark,
 } from "./internals.ts";
 import * as sym from "./symbols.ts";
-import { WritableStreamDefaultControllerImpl } from "./writable_stream_default_controller.ts";
-import { WritableStreamDefaultWriterImpl } from "./writable_stream_default_writer.ts";
+import type { WritableStreamDefaultControllerImpl } from "./writable_stream_default_controller.ts";
+import type { WritableStreamDefaultWriterImpl } from "./writable_stream_default_writer.ts";
 import { customInspect } from "../console.ts";
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
diff --git a/cli/js/web/streams/writable_stream_default_controller.ts b/cli/js/web/streams/writable_stream_default_controller.ts
index 040d0eefc..b957c2c8f 100644
--- a/cli/js/web/streams/writable_stream_default_controller.ts
+++ b/cli/js/web/streams/writable_stream_default_controller.ts
@@ -13,7 +13,7 @@ import {
   writableStreamDefaultControllerError,
 } from "./internals.ts";
 import * as sym from "./symbols.ts";
-import { WritableStreamImpl } from "./writable_stream.ts";
+import type { WritableStreamImpl } from "./writable_stream.ts";
 import { customInspect } from "../console.ts";
 
 export class WritableStreamDefaultControllerImpl<W>
diff --git a/cli/js/web/streams/writable_stream_default_writer.ts b/cli/js/web/streams/writable_stream_default_writer.ts
index 444a77aa9..09b47c69f 100644
--- a/cli/js/web/streams/writable_stream_default_writer.ts
+++ b/cli/js/web/streams/writable_stream_default_writer.ts
@@ -16,7 +16,7 @@ import {
   writableStreamDefaultWriterWrite,
 } from "./internals.ts";
 import * as sym from "./symbols.ts";
-import { WritableStreamImpl } from "./writable_stream.ts";
+import type { WritableStreamImpl } from "./writable_stream.ts";
 import { customInspect } from "../console.ts";
 import { assert } from "../../util.ts";
 
diff --git a/cli/msg.rs b/cli/msg.rs
index 3e5000296..5c50c96ab 100644
--- a/cli/msg.rs
+++ b/cli/msg.rs
@@ -55,10 +55,11 @@ pub fn enum_name_media_type(mt: MediaType) -> &'static str {
 #[derive(Clone, Copy, PartialEq, Debug)]
 pub enum CompilerRequestType {
   Compile = 0,
-  Bundle = 1,
-  RuntimeCompile = 2,
-  RuntimeBundle = 3,
-  RuntimeTranspile = 4,
+  Transpile = 1,
+  Bundle = 2,
+  RuntimeCompile = 3,
+  RuntimeBundle = 4,
+  RuntimeTranspile = 5,
 }
 
 impl Serialize for CompilerRequestType {
@@ -68,10 +69,11 @@ impl Serialize for CompilerRequestType {
   {
     let value: i32 = match self {
       CompilerRequestType::Compile => 0 as i32,
-      CompilerRequestType::Bundle => 1 as i32,
-      CompilerRequestType::RuntimeCompile => 2 as i32,
-      CompilerRequestType::RuntimeBundle => 3 as i32,
-      CompilerRequestType::RuntimeTranspile => 4 as i32,
+      CompilerRequestType::Transpile => 1 as i32,
+      CompilerRequestType::Bundle => 2 as i32,
+      CompilerRequestType::RuntimeCompile => 3 as i32,
+      CompilerRequestType::RuntimeBundle => 4 as i32,
+      CompilerRequestType::RuntimeTranspile => 5 as i32,
     };
     Serialize::serialize(&value, serializer)
   }
diff --git a/cli/tests/error_no_check.ts b/cli/tests/error_no_check.ts
new file mode 100644
index 000000000..db9257a1d
--- /dev/null
+++ b/cli/tests/error_no_check.ts
@@ -0,0 +1 @@
+export { AnInterface, isAnInterface } from "./subdir/type_and_code.ts";
diff --git a/cli/tests/error_no_check.ts.out b/cli/tests/error_no_check.ts.out
new file mode 100644
index 000000000..5890d1db8
--- /dev/null
+++ b/cli/tests/error_no_check.ts.out
@@ -0,0 +1 @@
+error: Uncaught SyntaxError: The requested module './subdir/type_and_code.ts' does not provide an export named 'AnInterface'
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index 562c25de2..9acb4ed3f 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -16,6 +16,7 @@ use tempfile::TempDir;
 fn std_tests() {
   let dir = TempDir::new().expect("tempdir fail");
   let std_path = util::root_path().join("std");
+  let std_config = std_path.join("tsconfig_test.json");
   let status = util::deno_cmd()
     .env("DENO_DIR", dir.path())
     .current_dir(std_path) // TODO(ry) change this to root_path
@@ -23,6 +24,8 @@ fn std_tests() {
     .arg("--unstable")
     .arg("--seed=86") // Some tests rely on specific random numbers.
     .arg("-A")
+    .arg("--config")
+    .arg(std_config.to_str().unwrap())
     // .arg("-Ldebug")
     .spawn()
     .unwrap()
@@ -1832,6 +1835,12 @@ itest!(error_025_tab_indent {
   exit_code: 1,
 });
 
+itest!(error_no_check {
+  args: "run --reload --no-check error_no_check.ts",
+  output: "error_no_check.ts.out",
+  exit_code: 1,
+});
+
 itest!(error_syntax {
   args: "run --reload error_syntax.js",
   exit_code: 1,
@@ -1890,6 +1899,12 @@ itest!(main_module {
   output: "main_module.ts.out",
 });
 
+itest!(no_check {
+  args: "run --quiet --reload --no-check 006_url_imports.ts",
+  output: "006_url_imports.ts.out",
+  http_server: true,
+});
+
 itest!(lib_ref {
   args: "run --quiet --unstable --reload lib_ref.ts",
   output: "lib_ref.ts.out",
diff --git a/cli/tests/subdir/type_and_code.ts b/cli/tests/subdir/type_and_code.ts
new file mode 100644
index 000000000..b14713419
--- /dev/null
+++ b/cli/tests/subdir/type_and_code.ts
@@ -0,0 +1,7 @@
+export interface AnInterface {
+  a: string;
+}
+
+export function isAnInterface(value: unknown): value is AnInterface {
+  return value && typeof value === "object" && "a" in value;
+}
diff --git a/cli/tsc.rs b/cli/tsc.rs
index 9f8216e52..2a1307432 100644
--- a/cli/tsc.rs
+++ b/cli/tsc.rs
@@ -302,6 +302,13 @@ impl CompiledFileMetadata {
   }
 }
 
+#[derive(Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+struct TranspileSourceFile {
+  pub source_code: String,
+  pub file_name: String,
+}
+
 /// Emit a SHA256 hash based on source code, deno version and TS config.
 /// Used to check if a recompilation for source code is needed.
 fn source_code_version_hash(
@@ -376,6 +383,13 @@ struct CompileResponse {
   build_info: Option<String>,
   stats: Option<Vec<Stat>>,
 }
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct TranspileResponse {
+  diagnostics: Diagnostic,
+  emit_map: HashMap<String, EmittedSource>,
+  stats: Option<Vec<Stat>>,
+}
 
 // TODO(bartlomieju): possible deduplicate once TS refactor is stabilized
 #[derive(Deserialize)]
@@ -704,6 +718,72 @@ impl TsCompiler {
     Ok(output)
   }
 
+  pub async fn transpile(
+    &self,
+    global_state: GlobalState,
+    permissions: Permissions,
+    module_graph: ModuleGraph,
+  ) -> Result<(), ErrBox> {
+    let mut source_files: Vec<TranspileSourceFile> = Vec::new();
+    for (_, value) in module_graph.iter() {
+      let url = Url::parse(&value.url).expect("Filename is not a valid url");
+      if !value.url.ends_with(".d.ts")
+        && (!self.use_disk_cache || !self.has_compiled_source(&url))
+      {
+        source_files.push(TranspileSourceFile {
+          source_code: value.source_code.clone(),
+          file_name: value.url.clone(),
+        });
+      }
+    }
+    if source_files.is_empty() {
+      return Ok(());
+    }
+
+    let source_files_json =
+      serde_json::to_value(source_files).expect("Filed to serialize data");
+    let compiler_config = self.config.clone();
+    let cwd = std::env::current_dir().unwrap();
+    let performance = match global_state.flags.log_level {
+      Some(Level::Debug) => true,
+      _ => false,
+    };
+    let j = match (compiler_config.path, compiler_config.content) {
+      (Some(config_path), Some(config_data)) => json!({
+        "config": str::from_utf8(&config_data).unwrap(),
+        "configPath": config_path,
+        "cwd": cwd,
+        "performance": performance,
+        "sourceFiles": source_files_json,
+        "type": msg::CompilerRequestType::Transpile,
+      }),
+      _ => json!({
+        "performance": performance,
+        "sourceFiles": source_files_json,
+        "type": msg::CompilerRequestType::Transpile,
+      }),
+    };
+
+    let req_msg = j.to_string().into_boxed_str().into_boxed_bytes();
+
+    let msg =
+      execute_in_same_thread(global_state.clone(), permissions, req_msg)
+        .await?;
+
+    let json_str = std::str::from_utf8(&msg).unwrap();
+
+    let transpile_response: TranspileResponse = serde_json::from_str(json_str)?;
+
+    if !transpile_response.diagnostics.items.is_empty() {
+      return Err(ErrBox::from(transpile_response.diagnostics));
+    }
+
+    maybe_log_stats(transpile_response.stats);
+
+    self.cache_emitted_files(transpile_response.emit_map)?;
+    Ok(())
+  }
+
   /// Get associated `CompiledFileMetadata` for given module if it exists.
   fn get_metadata(&self, url: &Url) -> Option<CompiledFileMetadata> {
     // Try to load cached version:
@@ -1575,6 +1655,75 @@ mod tests {
   }
 
   #[tokio::test]
+  async fn test_transpile() {
+    let p = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+      .parent()
+      .unwrap()
+      .join("cli/tests/002_hello.ts");
+    let specifier =
+      ModuleSpecifier::resolve_url_or_path(p.to_str().unwrap()).unwrap();
+    let out = SourceFile {
+      url: specifier.as_url().clone(),
+      filename: PathBuf::from(p.to_str().unwrap().to_string()),
+      media_type: msg::MediaType::TypeScript,
+      source_code: include_bytes!("./tests/002_hello.ts").to_vec(),
+      types_header: None,
+    };
+    let dir =
+      deno_dir::DenoDir::new(Some(test_util::new_deno_dir().path().to_owned()))
+        .unwrap();
+    let http_cache = http_cache::HttpCache::new(&dir.root.join("deps"));
+    let mock_state = GlobalState::mock(
+      vec![String::from("deno"), String::from("hello.ts")],
+      None,
+    );
+    let file_fetcher = SourceFileFetcher::new(
+      http_cache,
+      true,
+      mock_state.flags.cache_blocklist.clone(),
+      false,
+      false,
+      None,
+    )
+    .unwrap();
+
+    let mut module_graph_loader = ModuleGraphLoader::new(
+      file_fetcher.clone(),
+      None,
+      Permissions::allow_all(),
+      false,
+      false,
+    );
+    module_graph_loader
+      .add_to_graph(&specifier, None)
+      .await
+      .expect("Failed to create graph");
+    let module_graph = module_graph_loader.get_graph();
+
+    let ts_compiler = TsCompiler::new(
+      file_fetcher,
+      mock_state.flags.clone(),
+      dir.gen_cache.clone(),
+    )
+    .unwrap();
+
+    let result = ts_compiler
+      .transpile(mock_state.clone(), Permissions::allow_all(), module_graph)
+      .await;
+    assert!(result.is_ok());
+    let compiled_file = ts_compiler.get_compiled_module(&out.url).unwrap();
+    let source_code = compiled_file.code;
+    assert!(source_code
+      .as_bytes()
+      .starts_with(b"console.log(\"Hello World\");"));
+    let mut lines: Vec<String> =
+      source_code.split('\n').map(|s| s.to_string()).collect();
+    let last_line = lines.pop().unwrap();
+    assert!(last_line
+      .starts_with("//# sourceMappingURL=data:application/json;base64"));
+  }
+
+  #[tokio::test]
   async fn test_bundle() {
     let p = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
       .parent()
diff --git a/deno_typescript/lib.rs b/deno_typescript/lib.rs
index 25e5a7fd0..54d9b1d3b 100644
--- a/deno_typescript/lib.rs
+++ b/deno_typescript/lib.rs
@@ -148,6 +148,11 @@ pub fn compile_bundle(
   let config_json = serde_json::json!({
     "compilerOptions": {
       "declaration": true,
+      // In order to help ensure there are no type directed emits in the code
+      // which interferes with transpiling only, the setting
+      // `"importsNotUsedAsValues"` set to `"error"` will help ensure that items
+      // that are written as `import type` are caught and are treated as errors.
+      "importsNotUsedAsValues": "error",
       // Emit the source alongside the sourcemaps within a single file;
       // requires --inlineSourceMap or --sourceMap to be set.
       // "inlineSources": true,
diff --git a/std/encoding/_yaml/dumper/dumper.ts b/std/encoding/_yaml/dumper/dumper.ts
index 1280ee757..2b23d4758 100644
--- a/std/encoding/_yaml/dumper/dumper.ts
+++ b/std/encoding/_yaml/dumper/dumper.ts
@@ -6,7 +6,7 @@
 /* eslint-disable max-len */
 
 import { YAMLError } from "../error.ts";
-import { RepresentFn, StyleVariant, Type } from "../type.ts";
+import type { RepresentFn, StyleVariant, Type } from "../type.ts";
 import * as common from "../utils.ts";
 import { DumperState, DumperStateOptions } from "./dumper_state.ts";
 
diff --git a/std/encoding/_yaml/dumper/dumper_state.ts b/std/encoding/_yaml/dumper/dumper_state.ts
index 3c1de0e0e..2124ecb98 100644
--- a/std/encoding/_yaml/dumper/dumper_state.ts
+++ b/std/encoding/_yaml/dumper/dumper_state.ts
@@ -3,10 +3,10 @@
 // Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { Schema, SchemaDefinition } from "../schema.ts";
+import type { Schema, SchemaDefinition } from "../schema.ts";
 import { State } from "../state.ts";
-import { StyleVariant, Type } from "../type.ts";
-import { ArrayObject, Any } from "../utils.ts";
+import type { StyleVariant, Type } from "../type.ts";
+import type { ArrayObject, Any } from "../utils.ts";
 
 const _hasOwnProperty = Object.prototype.hasOwnProperty;
 
diff --git a/std/encoding/_yaml/error.ts b/std/encoding/_yaml/error.ts
index 7f305ccf2..a96ab11d6 100644
--- a/std/encoding/_yaml/error.ts
+++ b/std/encoding/_yaml/error.ts
@@ -3,7 +3,7 @@
 // Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { Mark } from "./mark.ts";
+import type { Mark } from "./mark.ts";
 
 export class YAMLError extends Error {
   constructor(
diff --git a/std/encoding/_yaml/loader/loader.ts b/std/encoding/_yaml/loader/loader.ts
index 39954c280..4ab3e9adc 100644
--- a/std/encoding/_yaml/loader/loader.ts
+++ b/std/encoding/_yaml/loader/loader.ts
@@ -7,7 +7,7 @@
 
 import { YAMLError } from "../error.ts";
 import { Mark } from "../mark.ts";
-import { Type } from "../type.ts";
+import type { Type } from "../type.ts";
 import * as common from "../utils.ts";
 import { LoaderState, LoaderStateOptions, ResultType } from "./loader_state.ts";
 
diff --git a/std/encoding/_yaml/loader/loader_state.ts b/std/encoding/_yaml/loader/loader_state.ts
index ca50fcaf1..781a4a086 100644
--- a/std/encoding/_yaml/loader/loader_state.ts
+++ b/std/encoding/_yaml/loader/loader_state.ts
@@ -3,11 +3,11 @@
 // Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { YAMLError } from "../error.ts";
-import { Schema, SchemaDefinition, TypeMap } from "../schema.ts";
+import type { YAMLError } from "../error.ts";
+import type { Schema, SchemaDefinition, TypeMap } from "../schema.ts";
 import { State } from "../state.ts";
-import { Type } from "../type.ts";
-import { Any, ArrayObject } from "../utils.ts";
+import type { Type } from "../type.ts";
+import type { Any, ArrayObject } from "../utils.ts";
 
 export interface LoaderStateOptions {
   legacy?: boolean;
diff --git a/std/encoding/_yaml/parse.ts b/std/encoding/_yaml/parse.ts
index 2aa0042bd..9a6f325f2 100644
--- a/std/encoding/_yaml/parse.ts
+++ b/std/encoding/_yaml/parse.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { CbFunction, load, loadAll } from "./loader/loader.ts";
-import { LoaderStateOptions } from "./loader/loader_state.ts";
+import type { LoaderStateOptions } from "./loader/loader_state.ts";
 
 export type ParseOptions = LoaderStateOptions;
 
diff --git a/std/encoding/_yaml/schema.ts b/std/encoding/_yaml/schema.ts
index 579644dbb..98b49203c 100644
--- a/std/encoding/_yaml/schema.ts
+++ b/std/encoding/_yaml/schema.ts
@@ -4,8 +4,8 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { YAMLError } from "./error.ts";
-import { KindType, Type } from "./type.ts";
-import { ArrayObject, Any } from "./utils.ts";
+import type { KindType, Type } from "./type.ts";
+import type { ArrayObject, Any } from "./utils.ts";
 
 function compileList(
   schema: Schema,
diff --git a/std/encoding/_yaml/state.ts b/std/encoding/_yaml/state.ts
index 6df6dc047..67a105d39 100644
--- a/std/encoding/_yaml/state.ts
+++ b/std/encoding/_yaml/state.ts
@@ -3,7 +3,7 @@
 // Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { SchemaDefinition } from "./schema.ts";
+import type { SchemaDefinition } from "./schema.ts";
 import { DEFAULT_SCHEMA } from "./schema/mod.ts";
 
 export abstract class State {
diff --git a/std/encoding/_yaml/stringify.ts b/std/encoding/_yaml/stringify.ts
index f037631d9..9b3b5a80e 100644
--- a/std/encoding/_yaml/stringify.ts
+++ b/std/encoding/_yaml/stringify.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { dump } from "./dumper/dumper.ts";
-import { DumperStateOptions } from "./dumper/dumper_state.ts";
+import type { DumperStateOptions } from "./dumper/dumper_state.ts";
 
 export type DumpOptions = DumperStateOptions;
 
diff --git a/std/encoding/_yaml/type.ts b/std/encoding/_yaml/type.ts
index 4a2c6bbac..18dee338c 100644
--- a/std/encoding/_yaml/type.ts
+++ b/std/encoding/_yaml/type.ts
@@ -3,7 +3,7 @@
 // Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { ArrayObject, Any } from "./utils.ts";
+import type { ArrayObject, Any } from "./utils.ts";
 
 export type KindType = "sequence" | "scalar" | "mapping";
 export type StyleVariant = "lowercase" | "uppercase" | "camelcase" | "decimal";
diff --git a/std/encoding/_yaml/type/binary.ts b/std/encoding/_yaml/type/binary.ts
index 1a321afe8..2433960dc 100644
--- a/std/encoding/_yaml/type/binary.ts
+++ b/std/encoding/_yaml/type/binary.ts
@@ -3,7 +3,7 @@
 // https://github.com/nodeca/js-yaml/commit/665aadda42349dcae869f12040d9b10ef18d12da
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { Type } from "../type.ts";
-import { Any } from "../utils.ts";
+import type { Any } from "../utils.ts";
 
 // [ 64, 65, 66 ] -> [ padding, CR, LF ]
 const BASE64_MAP =
diff --git a/std/encoding/_yaml/type/map.ts b/std/encoding/_yaml/type/map.ts
index dcd99abca..c0c8b04b7 100644
--- a/std/encoding/_yaml/type/map.ts
+++ b/std/encoding/_yaml/type/map.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { Type } from "../type.ts";
-import { Any } from "../utils.ts";
+import type { Any } from "../utils.ts";
 
 export const map = new Type("tag:yaml.org,2002:map", {
   construct(data): Any {
diff --git a/std/encoding/_yaml/type/omap.ts b/std/encoding/_yaml/type/omap.ts
index d6d751505..785846dea 100644
--- a/std/encoding/_yaml/type/omap.ts
+++ b/std/encoding/_yaml/type/omap.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { Type } from "../type.ts";
-import { Any } from "../utils.ts";
+import type { Any } from "../utils.ts";
 
 const _hasOwnProperty = Object.prototype.hasOwnProperty;
 const _toString = Object.prototype.toString;
diff --git a/std/encoding/_yaml/type/pairs.ts b/std/encoding/_yaml/type/pairs.ts
index e999748ae..5e3eac5ce 100644
--- a/std/encoding/_yaml/type/pairs.ts
+++ b/std/encoding/_yaml/type/pairs.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { Type } from "../type.ts";
-import { Any } from "../utils.ts";
+import type { Any } from "../utils.ts";
 
 const _toString = Object.prototype.toString;
 
diff --git a/std/encoding/_yaml/type/seq.ts b/std/encoding/_yaml/type/seq.ts
index b19565dbc..df2caaece 100644
--- a/std/encoding/_yaml/type/seq.ts
+++ b/std/encoding/_yaml/type/seq.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { Type } from "../type.ts";
-import { Any } from "../utils.ts";
+import type { Any } from "../utils.ts";
 
 export const seq = new Type("tag:yaml.org,2002:seq", {
   construct(data): Any {
diff --git a/std/encoding/_yaml/type/set.ts b/std/encoding/_yaml/type/set.ts
index 0bfe1c8db..8fe04e6f0 100644
--- a/std/encoding/_yaml/type/set.ts
+++ b/std/encoding/_yaml/type/set.ts
@@ -4,7 +4,7 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { Type } from "../type.ts";
-import { Any } from "../utils.ts";
+import type { Any } from "../utils.ts";
 
 const _hasOwnProperty = Object.prototype.hasOwnProperty;
 
diff --git a/std/encoding/yaml.ts b/std/encoding/yaml.ts
index 78866ed2a..19245b2fc 100644
--- a/std/encoding/yaml.ts
+++ b/std/encoding/yaml.ts
@@ -3,13 +3,12 @@
 // Copyright 2011-2015 by Vitaly Puzrin. All rights reserved. MIT license.
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-export { ParseOptions, parse, parseAll } from "./_yaml/parse.ts";
-export {
-  DumpOptions as StringifyOptions,
-  stringify,
-} from "./_yaml/stringify.ts";
-export { SchemaDefinition } from "./_yaml/schema.ts";
-export { StyleVariant } from "./_yaml/type.ts";
+export type { ParseOptions } from "./_yaml/parse.ts";
+export { parse, parseAll } from "./_yaml/parse.ts";
+export type { DumpOptions as StringifyOptions } from "./_yaml/stringify.ts";
+export { stringify } from "./_yaml/stringify.ts";
+export type { SchemaDefinition } from "./_yaml/schema.ts";
+export type { StyleVariant } from "./_yaml/type.ts";
 export {
   CORE_SCHEMA,
   DEFAULT_SCHEMA,
diff --git a/std/hash/_wasm/hash.ts b/std/hash/_wasm/hash.ts
index d04a4d4a0..43ddf77f3 100644
--- a/std/hash/_wasm/hash.ts
+++ b/std/hash/_wasm/hash.ts
@@ -10,7 +10,7 @@ import init, {
 
 import * as hex from "../../encoding/hex.ts";
 import * as base64 from "../../encoding/base64.ts";
-import { Hasher, Message, OutputFormat } from "../hasher.ts";
+import type { Hasher, Message, OutputFormat } from "../hasher.ts";
 
 await init(source);
 
diff --git a/std/hash/mod.ts b/std/hash/mod.ts
index 946769f03..06c9ce439 100644
--- a/std/hash/mod.ts
+++ b/std/hash/mod.ts
@@ -1,9 +1,9 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
 import { Hash } from "./_wasm/hash.ts";
-import { Hasher } from "./hasher.ts";
+import type { Hasher } from "./hasher.ts";
 
-export { Hasher } from "./hasher.ts";
+export type { Hasher } from "./hasher.ts";
 export type SupportedAlgorithm =
   | "md2"
   | "md4"
diff --git a/std/io/ioutil.ts b/std/io/ioutil.ts
index 3d9e72b56..ac6d103a3 100644
--- a/std/io/ioutil.ts
+++ b/std/io/ioutil.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { BufReader } from "./bufio.ts";
+import type { BufReader } from "./bufio.ts";
 type Reader = Deno.Reader;
 type Writer = Deno.Writer;
 import { assert } from "../_util/assert.ts";
diff --git a/std/log/handlers.ts b/std/log/handlers.ts
index 0efa7cc26..e09dc648c 100644
--- a/std/log/handlers.ts
+++ b/std/log/handlers.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 import { getLevelByName, LevelName, LogLevels } from "./levels.ts";
-import { LogRecord } from "./logger.ts";
+import type { LogRecord } from "./logger.ts";
 import { red, yellow, blue, bold } from "../fmt/colors.ts";
 import { existsSync, exists } from "../fs/exists.ts";
 import { BufWriterSync } from "../io/bufio.ts";
diff --git a/std/log/logger.ts b/std/log/logger.ts
index 05e83dc77..482047f2a 100644
--- a/std/log/logger.ts
+++ b/std/log/logger.ts
@@ -5,7 +5,7 @@ import {
   getLevelName,
   LevelName,
 } from "./levels.ts";
-import { BaseHandler } from "./handlers.ts";
+import type { BaseHandler } from "./handlers.ts";
 
 export interface LogRecordOptions {
   msg: string;
diff --git a/std/log/mod.ts b/std/log/mod.ts
index ed94725c4..9565749aa 100644
--- a/std/log/mod.ts
+++ b/std/log/mod.ts
@@ -8,7 +8,7 @@ import {
   RotatingFileHandler,
 } from "./handlers.ts";
 import { assert } from "../_util/assert.ts";
-import { LevelName } from "./levels.ts";
+import type { LevelName } from "./levels.ts";
 
 export { LogLevels, LevelName } from "./levels.ts";
 export { Logger } from "./logger.ts";
diff --git a/std/node/_fs/_fs_access.ts b/std/node/_fs/_fs_access.ts
index ee93c4c7f..79e4ca96d 100644
--- a/std/node/_fs/_fs_access.ts
+++ b/std/node/_fs/_fs_access.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 import { notImplemented } from "../_utils.ts";
 
 /** Revist once https://github.com/denoland/deno/issues/4017 lands */
diff --git a/std/node/_fs/_fs_chmod.ts b/std/node/_fs/_fs_chmod.ts
index b1079e0a1..844afd21d 100644
--- a/std/node/_fs/_fs_chmod.ts
+++ b/std/node/_fs/_fs_chmod.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 import { fromFileUrl } from "../path.ts";
 
 const allowedModes = /^[0-7]{3}/;
diff --git a/std/node/_fs/_fs_chown.ts b/std/node/_fs/_fs_chown.ts
index cd1973b1f..56068ef73 100644
--- a/std/node/_fs/_fs_chown.ts
+++ b/std/node/_fs/_fs_chown.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 import { fromFileUrl } from "../path.ts";
 
 /**
diff --git a/std/node/_fs/_fs_close.ts b/std/node/_fs/_fs_close.ts
index cdd815ad9..add6f6663 100644
--- a/std/node/_fs/_fs_close.ts
+++ b/std/node/_fs/_fs_close.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 
 export function close(fd: number, callback: CallbackWithError): void {
   queueMicrotask(() => {
diff --git a/std/node/_fs/_fs_copy.ts b/std/node/_fs/_fs_copy.ts
index 26d9a8c9a..72f43d18f 100644
--- a/std/node/_fs/_fs_copy.ts
+++ b/std/node/_fs/_fs_copy.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 import { fromFileUrl } from "../path.ts";
 
 export function copyFile(
diff --git a/std/node/_fs/_fs_dir_test.ts b/std/node/_fs/_fs_dir_test.ts
index e89912772..2d2d5f585 100644
--- a/std/node/_fs/_fs_dir_test.ts
+++ b/std/node/_fs/_fs_dir_test.ts
@@ -1,6 +1,6 @@
 import { assert, assertEquals, fail } from "../../testing/asserts.ts";
 import Dir from "./_fs_dir.ts";
-import Dirent from "./_fs_dirent.ts";
+import type Dirent from "./_fs_dirent.ts";
 
 Deno.test({
   name: "Closing current directory with callback is successful",
diff --git a/std/node/_fs/_fs_link.ts b/std/node/_fs/_fs_link.ts
index 50916a7ba..df08e13b1 100644
--- a/std/node/_fs/_fs_link.ts
+++ b/std/node/_fs/_fs_link.ts
@@ -1,6 +1,6 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
 
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 import { fromFileUrl } from "../path.ts";
 
 /**
diff --git a/std/node/_fs/_fs_mkdir.ts b/std/node/_fs/_fs_mkdir.ts
index a65db8dba..8578f4653 100644
--- a/std/node/_fs/_fs_mkdir.ts
+++ b/std/node/_fs/_fs_mkdir.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { CallbackWithError } from "./_fs_common.ts";
+import type { CallbackWithError } from "./_fs_common.ts";
 import { fromFileUrl } from "../path.ts";
 
 /**
@@ -31,10 +31,11 @@ export function mkdir(
     if (options.recursive !== undefined) recursive = options.recursive;
     if (options.mode !== undefined) mode = options.mode;
   }
-  if (typeof recursive !== "boolean")
+  if (typeof recursive !== "boolean") {
     throw new Deno.errors.InvalidData(
       "invalid recursive option , must be a boolean"
     );
+  }
   Deno.mkdir(path, { recursive, mode })
     .then(() => {
       if (typeof callback === "function") {
@@ -61,10 +62,11 @@ export function mkdirSync(path: string | URL, options?: MkdirOptions): void {
     if (options.recursive !== undefined) recursive = options.recursive;
     if (options.mode !== undefined) mode = options.mode;
   }
-  if (typeof recursive !== "boolean")
+  if (typeof recursive !== "boolean") {
     throw new Deno.errors.InvalidData(
       "invalid recursive option , must be a boolean"
     );
+  }
 
   Deno.mkdirSync(path, { recursive, mode });
 }
diff --git a/std/node/_fs/_fs_writeFile_test.ts b/std/node/_fs/_fs_writeFile_test.ts
index 3959ad219..015ed6553 100644
--- a/std/node/_fs/_fs_writeFile_test.ts
+++ b/std/node/_fs/_fs_writeFile_test.ts
@@ -6,7 +6,7 @@ import {
   assertThrows,
 } from "../../testing/asserts.ts";
 import { writeFile, writeFileSync } from "./_fs_writeFile.ts";
-import { TextEncodings } from "./_fs_common.ts";
+import type { TextEncodings } from "./_fs_common.ts";
 import * as path from "../../path/mod.ts";
 
 const testDataDir = path.resolve(path.join("node", "_fs", "testdata"));
diff --git a/std/node/_fs/promises/_fs_readFile.ts b/std/node/_fs/promises/_fs_readFile.ts
index 83ef9ac50..8677e05cd 100644
--- a/std/node/_fs/promises/_fs_readFile.ts
+++ b/std/node/_fs/promises/_fs_readFile.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import {
+import type {
   FileOptionsArgument,
   BinaryOptionsArgument,
   TextOptionsArgument,
@@ -21,8 +21,9 @@ export function readFile(
   return new Promise((resolve, reject) => {
     readFileCallback(path, options, (err, data): void => {
       if (err) return reject(err);
-      if (data == null)
+      if (data == null) {
         return reject(new Error("Invalid state: data missing, but no error"));
+      }
       resolve(data);
     });
   });
diff --git a/std/node/_fs/promises/_fs_writeFile.ts b/std/node/_fs/promises/_fs_writeFile.ts
index 4f7c39a6a..48b9bf0ea 100644
--- a/std/node/_fs/promises/_fs_writeFile.ts
+++ b/std/node/_fs/promises/_fs_writeFile.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { Encodings, WriteFileOptions } from "../_fs_common.ts";
+import type { Encodings, WriteFileOptions } from "../_fs_common.ts";
 
 import { writeFile as writeFileCallback } from "../_fs_writeFile.ts";
 
diff --git a/std/node/_fs/promises/_fs_writeFile_test.ts b/std/node/_fs/promises/_fs_writeFile_test.ts
index 8f6ef0842..6901fff22 100644
--- a/std/node/_fs/promises/_fs_writeFile_test.ts
+++ b/std/node/_fs/promises/_fs_writeFile_test.ts
@@ -6,7 +6,7 @@ import {
   assertThrowsAsync,
 } from "../../../testing/asserts.ts";
 import { writeFile } from "./_fs_writeFile.ts";
-import { TextEncodings } from "../_fs_common.ts";
+import type { TextEncodings } from "../_fs_common.ts";
 
 const decoder = new TextDecoder("utf-8");
 
diff --git a/std/path/_util.ts b/std/path/_util.ts
index 8ae40373b..0c3253045 100644
--- a/std/path/_util.ts
+++ b/std/path/_util.ts
@@ -2,7 +2,7 @@
 // Ported from https://github.com/browserify/path-browserify/
 /** This module is browser compatible. */
 
-import { FormatInputPathObject } from "./_interface.ts";
+import type { FormatInputPathObject } from "./_interface.ts";
 import {
   CHAR_UPPERCASE_A,
   CHAR_LOWERCASE_A,
diff --git a/std/path/posix.ts b/std/path/posix.ts
index 1e78d1cfe..351ceb06e 100644
--- a/std/path/posix.ts
+++ b/std/path/posix.ts
@@ -2,7 +2,7 @@
 // Ported from https://github.com/browserify/path-browserify/
 /** This module is browser compatible. */
 
-import { FormatInputPathObject, ParsedPath } from "./_interface.ts";
+import type { FormatInputPathObject, ParsedPath } from "./_interface.ts";
 import { CHAR_DOT, CHAR_FORWARD_SLASH } from "./_constants.ts";
 
 import {
diff --git a/std/path/win32.ts b/std/path/win32.ts
index bac43a61a..30482e453 100644
--- a/std/path/win32.ts
+++ b/std/path/win32.ts
@@ -2,7 +2,7 @@
 // Ported from https://github.com/browserify/path-browserify/
 /** This module is browser compatible. */
 
-import { FormatInputPathObject, ParsedPath } from "./_interface.ts";
+import type { FormatInputPathObject, ParsedPath } from "./_interface.ts";
 import {
   CHAR_DOT,
   CHAR_BACKWARD_SLASH,
diff --git a/std/textproto/mod.ts b/std/textproto/mod.ts
index f440ba5d5..1d0d22715 100644
--- a/std/textproto/mod.ts
+++ b/std/textproto/mod.ts
@@ -3,7 +3,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-import { BufReader } from "../io/bufio.ts";
+import type { BufReader } from "../io/bufio.ts";
 import { concat } from "../bytes/mod.ts";
 import { decode } from "../encoding/utf8.ts";
 
diff --git a/std/tsconfig_test.json b/std/tsconfig_test.json
new file mode 100644
index 000000000..1dbf69fb2
--- /dev/null
+++ b/std/tsconfig_test.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "importsNotUsedAsValues": "error"
+  }
+}
diff --git a/tools/benchmark.py b/tools/benchmark.py
index 369aa6fca..b79f35ac8 100755
--- a/tools/benchmark.py
+++ b/tools/benchmark.py
@@ -31,6 +31,10 @@ exec_time_benchmarks = [
      ["run", "--allow-read", "cli/tests/workers_round_robin_bench.ts"], None),
     ("text_decoder", ["run", "cli/tests/text_decoder_perf.js"], None),
     ("text_encoder", ["run", "cli/tests/text_encoder_perf.js"], None),
+    ("check", ["cache", "--reload", "std/examples/chat/server_test.ts"], None),
+    ("no_check",
+     ["cache", "--reload", "--no-check",
+      "std/examples/chat/server_test.ts"], None),
 ]