From 36c5403fff6fed86e2fb75ba9a9e3f8bef2cd98c Mon Sep 17 00:00:00 2001
From: Pig Fang <g-plane@hotmail.com>
Date: Sat, 15 Jun 2019 10:54:47 +0800
Subject: [PATCH 1/3] Disallow "let" as name at lexical bindings

---
 packages/babel-parser/src/parser/statement.js | 25 +++++++++++++++++++
 .../let/let-at-binding-list-fail-1/input.js   |  1 +
 .../let-at-binding-list-fail-1/options.json   |  3 +++
 .../let/let-at-binding-list-fail-2/input.js   |  1 +
 .../let-at-binding-list-fail-2/options.json   |  3 +++
 .../let/let-at-binding-list-fail-3/input.js   |  1 +
 .../let-at-binding-list-fail-3/options.json   |  3 +++
 .../let/let-at-binding-list-fail-4/input.js   |  1 +
 .../let-at-binding-list-fail-4/options.json   |  3 +++
 9 files changed, 41 insertions(+)
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/options.json
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/options.json
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/options.json
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/options.json

diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
index f47b80448b10..8949822cbf74 100644
--- a/packages/babel-parser/src/parser/statement.js
+++ b/packages/babel-parser/src/parser/statement.js
@@ -1014,6 +1014,15 @@ export default class StatementParser extends ExpressionParser {
       this.unexpected(null, "let is disallowed as a lexically bound name");
     }
     decl.id = this.parseBindingAtom();
+    if (kind === "const" || kind === "let") {
+      const invalid = this.checkVarIdHasLet(decl.id);
+      if (invalid) {
+        this.raise(
+          invalid.start,
+          "'let' is not allowed to be used as a name in 'let' or 'const' declarations.",
+        );
+      }
+    }
     this.checkLVal(
       decl.id,
       kind === "var" ? BIND_VAR : BIND_LEXICAL,
@@ -1022,6 +1031,22 @@ export default class StatementParser extends ExpressionParser {
     );
   }
 
+  checkVarIdHasLet(id: ?N.Pattern): ?N.Identifier {
+    if (!id) {
+      return null;
+    } else if (id.type === "ArrayPattern") {
+      return id.elements.find(element => this.checkVarIdHasLet(element));
+    } else if (id.type === "ObjectPattern") {
+      return id.properties.find(property =>
+        this.checkVarIdHasLet(property.value),
+      );
+    } else if (id.type === "Identifier" && id.name === "let") {
+      return id;
+    } else {
+      return null;
+    }
+  }
+
   // Parse a function declaration or literal (depending on the
   // `isStatement` parameter).
 
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/input.js b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/input.js
new file mode 100644
index 000000000000..c1eb32d32577
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/input.js
@@ -0,0 +1 @@
+let { let } = {};
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/options.json b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/options.json
new file mode 100644
index 000000000000..f57eb3dfe6c2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-1/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'let' is not allowed to be used as a name in 'let' or 'const' declarations. (1:6)"
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/input.js b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/input.js
new file mode 100644
index 000000000000..24c395ad2c48
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/input.js
@@ -0,0 +1 @@
+const { let } = {};
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/options.json b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/options.json
new file mode 100644
index 000000000000..365d76ddf46e
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-2/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'let' is not allowed to be used as a name in 'let' or 'const' declarations. (1:8)"
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/input.js b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/input.js
new file mode 100644
index 000000000000..346cb602094b
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/input.js
@@ -0,0 +1 @@
+let [let] = [];
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/options.json b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/options.json
new file mode 100644
index 000000000000..d83275e4a85a
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-3/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'let' is not allowed to be used as a name in 'let' or 'const' declarations. (1:5)"
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/input.js b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/input.js
new file mode 100644
index 000000000000..8c5f4099aed6
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/input.js
@@ -0,0 +1 @@
+const [let] = [];
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/options.json b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/options.json
new file mode 100644
index 000000000000..456948bdd272
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-4/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'let' is not allowed to be used as a name in 'let' or 'const' declarations. (1:7)"
+}
\ No newline at end of file

From e93c823933063016c42b3f1e4cf4fac9ff8df4b9 Mon Sep 17 00:00:00 2001
From: Pig Fang <g-plane@hotmail.com>
Date: Sat, 15 Jun 2019 21:00:50 +0800
Subject: [PATCH 2/3] Simplify

---
 packages/babel-parser/src/parser/lval.js             |  8 +++++++-
 packages/babel-parser/src/parser/statement.js        | 12 ------------
 .../es2015/let/let-at-binding-list-fail-5/input.js   |  1 +
 .../let/let-at-binding-list-fail-5/options.json      |  3 +++
 .../es2015/let/let-at-binding-list-fail-6/input.js   |  1 +
 .../let/let-at-binding-list-fail-6/options.json      |  3 +++
 6 files changed, 15 insertions(+), 13 deletions(-)
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/options.json
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/input.js
 create mode 100644 packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/options.json

diff --git a/packages/babel-parser/src/parser/lval.js b/packages/babel-parser/src/parser/lval.js
index c50e5cc1414b..b4281ab2ffb7 100644
--- a/packages/babel-parser/src/parser/lval.js
+++ b/packages/babel-parser/src/parser/lval.js
@@ -16,7 +16,7 @@ import type {
 import type { Pos, Position } from "../util/location";
 import { isStrictBindReservedWord } from "../util/identifier";
 import { NodeUtils } from "./node";
-import { type BindingTypes, BIND_NONE } from "../util/scopeflags";
+import { type BindingTypes, BIND_NONE, BIND_LEXICAL } from "../util/scopeflags";
 
 export default class LValParser extends NodeUtils {
   // Forward-declaration: defined in expression.js
@@ -363,6 +363,12 @@ export default class LValParser extends NodeUtils {
             checkClashes[key] = true;
           }
         }
+        if (bindingType === BIND_LEXICAL && expr.name === "let") {
+          this.raise(
+            expr.start,
+            "'let' is not allowed to be used as a name in 'let' or 'const' declarations.",
+          );
+        }
         if (!(bindingType & BIND_NONE)) {
           this.scope.declareName(expr.name, bindingType, expr.start);
         }
diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
index 8949822cbf74..26e2de49406c 100644
--- a/packages/babel-parser/src/parser/statement.js
+++ b/packages/babel-parser/src/parser/statement.js
@@ -1010,19 +1010,7 @@ export default class StatementParser extends ExpressionParser {
   }
 
   parseVarId(decl: N.VariableDeclarator, kind: "var" | "let" | "const"): void {
-    if ((kind === "const" || kind === "let") && this.isContextual("let")) {
-      this.unexpected(null, "let is disallowed as a lexically bound name");
-    }
     decl.id = this.parseBindingAtom();
-    if (kind === "const" || kind === "let") {
-      const invalid = this.checkVarIdHasLet(decl.id);
-      if (invalid) {
-        this.raise(
-          invalid.start,
-          "'let' is not allowed to be used as a name in 'let' or 'const' declarations.",
-        );
-      }
-    }
     this.checkLVal(
       decl.id,
       kind === "var" ? BIND_VAR : BIND_LEXICAL,
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/input.js b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/input.js
new file mode 100644
index 000000000000..27fcc4afa2f1
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/input.js
@@ -0,0 +1 @@
+let let
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/options.json b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/options.json
new file mode 100644
index 000000000000..4ca932f989ae
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-5/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'let' is not allowed to be used as a name in 'let' or 'const' declarations. (1:4)"
+}
\ No newline at end of file
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/input.js b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/input.js
new file mode 100644
index 000000000000..9514d67a4443
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/input.js
@@ -0,0 +1 @@
+const let = ''
diff --git a/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/options.json b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/options.json
new file mode 100644
index 000000000000..f57eb3dfe6c2
--- /dev/null
+++ b/packages/babel-parser/test/fixtures/es2015/let/let-at-binding-list-fail-6/options.json
@@ -0,0 +1,3 @@
+{
+  "throws": "'let' is not allowed to be used as a name in 'let' or 'const' declarations. (1:6)"
+}
\ No newline at end of file

From 23ddcf007c7335b002686e4abbc3426a65b026e3 Mon Sep 17 00:00:00 2001
From: Pig Fang <g-plane@hotmail.com>
Date: Sat, 15 Jun 2019 21:02:05 +0800
Subject: [PATCH 3/3] Clean up

---
 packages/babel-parser/src/parser/statement.js | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/packages/babel-parser/src/parser/statement.js b/packages/babel-parser/src/parser/statement.js
index 26e2de49406c..ad29af252975 100644
--- a/packages/babel-parser/src/parser/statement.js
+++ b/packages/babel-parser/src/parser/statement.js
@@ -1019,22 +1019,6 @@ export default class StatementParser extends ExpressionParser {
     );
   }
 
-  checkVarIdHasLet(id: ?N.Pattern): ?N.Identifier {
-    if (!id) {
-      return null;
-    } else if (id.type === "ArrayPattern") {
-      return id.elements.find(element => this.checkVarIdHasLet(element));
-    } else if (id.type === "ObjectPattern") {
-      return id.properties.find(property =>
-        this.checkVarIdHasLet(property.value),
-      );
-    } else if (id.type === "Identifier" && id.name === "let") {
-      return id;
-    } else {
-      return null;
-    }
-  }
-
   // Parse a function declaration or literal (depending on the
   // `isStatement` parameter).