Add plugin for import.meta proposal

Fixes #539

README.md

@@ -139,6 +139,7 @@ require("babylon").parse("code", {
  - `functionSent`
  - `dynamicImport` ([proposal](https://github.com/tc39/proposal-dynamic-import))
  - `numericSeparator` ([proposal](https://github.com/samuelgoto/proposal-numeric-separator))
+ - `importMeta` ([proposal](https://github.com/tc39/proposal-import-meta))
 
 ### FAQ
 

src/parser/expression.js

@@ -427,6 +427,10 @@ export default class ExpressionParser extends LValParser {
         return this.finishNode(node, "Super");
 
       case tt._import:
+        if (this.hasPlugin("importMeta") && this.lookahead().type === tt.dot) {
+          return this.parseImportMetaProperty();
+        }
+
         if (!this.hasPlugin("dynamicImport")) this.unexpected();
 
         node = this.startNode();
@@ -594,6 +598,16 @@ export default class ExpressionParser extends LValParser {
     return this.finishNode(node, "MetaProperty");
   }
 
+  parseImportMetaProperty(): N.MetaProperty {
+    const node = this.startNode();
+    const id = this.parseIdentifier(true);
+    this.expect(tt.dot);
+    if (this.options.sourceType !== "module") {
+      this.raise(id.start, "import.meta can only be used in modules");
+    }
+    return this.parseMetaProperty(node, id, "meta");
+  }
+
   parseLiteral<T : N.Literal>(value: any, type: /*T["kind"]*/string, startPos?: number, startLoc?: Position): T {
     startPos = startPos || this.state.start;
     startLoc = startLoc || this.state.startLoc;

src/parser/statement.js

@@ -106,7 +106,8 @@ export default class StatementParser extends ExpressionParser {
       case tt.semi: return this.parseEmptyStatement(node);
       case tt._export:
       case tt._import:
-        if (this.hasPlugin("dynamicImport") && this.lookahead().type === tt.parenL) break;
+        if ((this.hasPlugin("dynamicImport") && this.lookahead().type === tt.parenL) ||
+            (this.hasPlugin("importMeta") && this.lookahead().type === tt.dot)) break;
 
         if (!this.options.allowImportExportEverywhere) {
           if (!topLevel) {

test/fixtures/experimental/import-meta/error-in-script/actual.js

@@ -0,0 +1 @@
+const x = import.meta;

test/fixtures/experimental/import-meta/error-in-script/options.json

@@ -0,0 +1,5 @@
+{
+  "throws": "import.meta can only be used in modules (1:10)",
+  "plugins": ["dynamicImport", "importMeta"],
+  "sourceType": "script"
+}

test/fixtures/experimental/import-meta/valid-in-module/actual.js

@@ -0,0 +1,4 @@
+const x = import.meta;
+const url = import.meta.url;
+import.meta;
+import.meta.url;