Implement ES2016 check for simple parameter list in strict mode (babe…

…l#106)

* Slightly simplify logic

* Implement ES2016 check for simple parameter list in strict mode

See e.g. ECMA-262 7.0 14.1.2:

> It is a Syntax Error if ContainsUseStrict of FunctionBody is true and
> IsSimpleParameterList of FormalParameters is false.

Similar clauses cover arrow functions, generator functions, methods, and
generator methods, as well as async functions and async arrow functions.

packages/babylon/src/parser/expression.js

@@ -885,7 +885,6 @@ pp.parseFunctionBody = function (node, allowExpression) {
   // are not repeated, and it does not try to bind the words `eval`
   // or `arguments`.
   let checkLVal = this.state.strict;
-  let checkLValStrict = false;
   let isStrict = false;
 
   // arrow function
@@ -897,7 +896,6 @@ pp.parseFunctionBody = function (node, allowExpression) {
       if (directive.value.value === "use strict") {
         isStrict = true;
         checkLVal = true;
-        checkLValStrict = true;
         break;
       }
     }
@@ -911,11 +909,14 @@ pp.parseFunctionBody = function (node, allowExpression) {
   if (checkLVal) {
     let nameHash = Object.create(null);
     let oldStrict = this.state.strict;
-    if (checkLValStrict) this.state.strict = true;
+    if (isStrict) this.state.strict = true;
     if (node.id) {
       this.checkLVal(node.id, true);
     }
     for (let param of (node.params: Array<Object>)) {
+      if (isStrict && param.type !== "Identifier") {
+        this.raise(param.start, "Non-simple parameter in strict mode");
+      }
       this.checkLVal(param, true, nameHash);
     }
     this.state.strict = oldStrict;

packages/babylon/test/fixtures/es2016/simple-parameter-list/array-pattern-default/actual.js

@@ -0,0 +1,3 @@
+function a([ option1, option2 ] = []) {
+  "use strict";
+}

packages/babylon/test/fixtures/es2016/simple-parameter-list/array-pattern-default/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Non-simple parameter in strict mode (1:11)"
+}

packages/babylon/test/fixtures/es2016/simple-parameter-list/array-pattern/actual.js

@@ -0,0 +1,3 @@
+function a([ option1, option2 ]) {
+  "use strict";
+}

packages/babylon/test/fixtures/es2016/simple-parameter-list/array-pattern/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Non-simple parameter in strict mode (1:11)"
+}

packages/babylon/test/fixtures/es2016/simple-parameter-list/arrow-function-concise-body/actual.js

@@ -0,0 +1 @@
+var a = (options = {}) => options;

packages/babylon/test/fixtures/es2016/simple-parameter-list/arrow-function-concise-body/expected.json

@@ -0,0 +1,170 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 34,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 34
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 34,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 34
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "VariableDeclaration",
+        "start": 0,
+        "end": 34,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 34
+          }
+        },
+        "declarations": [
+          {
+            "type": "VariableDeclarator",
+            "start": 4,
+            "end": 33,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 4
+              },
+              "end": {
+                "line": 1,
+                "column": 33
+              }
+            },
+            "id": {
+              "type": "Identifier",
+              "start": 4,
+              "end": 5,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 4
+                },
+                "end": {
+                  "line": 1,
+                  "column": 5
+                },
+                "identifierName": "a"
+              },
+              "name": "a"
+            },
+            "init": {
+              "type": "ArrowFunctionExpression",
+              "start": 8,
+              "end": 33,
+              "loc": {
+                "start": {
+                  "line": 1,
+                  "column": 8
+                },
+                "end": {
+                  "line": 1,
+                  "column": 33
+                }
+              },
+              "id": null,
+              "generator": false,
+              "expression": true,
+              "async": false,
+              "params": [
+                {
+                  "type": "AssignmentPattern",
+                  "start": 9,
+                  "end": 21,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 9
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 21
+                    }
+                  },
+                  "left": {
+                    "type": "Identifier",
+                    "start": 9,
+                    "end": 16,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 9
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 16
+                      },
+                      "identifierName": "options"
+                    },
+                    "name": "options"
+                  },
+                  "right": {
+                    "type": "ObjectExpression",
+                    "start": 19,
+                    "end": 21,
+                    "loc": {
+                      "start": {
+                        "line": 1,
+                        "column": 19
+                      },
+                      "end": {
+                        "line": 1,
+                        "column": 21
+                      }
+                    },
+                    "properties": []
+                  }
+                }
+              ],
+              "body": {
+                "type": "Identifier",
+                "start": 26,
+                "end": 33,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 26
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 33
+                  },
+                  "identifierName": "options"
+                },
+                "name": "options"
+              }
+            }
+          }
+        ],
+        "kind": "var"
+      }
+    ],
+    "directives": []
+  }
+}

packages/babylon/test/fixtures/es2016/simple-parameter-list/arrow-function/actual.js

@@ -0,0 +1,3 @@
+var a = (options = {}) => {
+  "use strict";
+};

packages/babylon/test/fixtures/es2016/simple-parameter-list/arrow-function/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "Non-simple parameter in strict mode (1:9)"
+}

packages/babylon/test/fixtures/es2016/simple-parameter-list/async-arrow-function-concise-body/actual.js

@@ -0,0 +1 @@
+var a = async (options = {}) => options;