Fix parsing error in exponent expressions with unary left-hand sides.

Esprima (correctly) rejects expressions like -1**2. However, expressions like (-1)**2 are valid but still rejected. This commit fixes this issue by identifying when the left operand is parenthesized. Fixes jquery#1981
luiscubal · Mar 8, 2021 · b04ee63 · b04ee63
1 parent 70c0159
commit b04ee63
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Showing 3 changed files with 250 additions and 1 deletion.
diff --git a/src/parser.ts b/src/parser.ts
@@ -1475,8 +1475,16 @@ export class Parser {
     parseExponentiationExpression(): Node.Expression {
         const startToken = this.lookahead;
 
+        // -1 ** 2 is not accepted, but (-1) ** 2
+        // However, the AST for both cases is identical
+        // We distinguish the two cases by explicitly checking for a parenthesis.
+
+        const isLeftParenthesized = this.match('(');
         let expr = this.inheritCoverGrammar(this.parseUnaryExpression);
-        if (expr.type !== Syntax.UnaryExpression && this.match('**')) {
+
+        const exponentAllowed = expr.type !== Syntax.UnaryExpression || isLeftParenthesized;
+
+        if (exponentAllowed && this.match('**')) {
             this.nextToken();
             this.context.isAssignmentTarget = false;
             this.context.isBindingElement = false;

diff --git a/test/fixtures/ES2016/exponent/exp_paren.js b/test/fixtures/ES2016/exponent/exp_paren.js
@@ -0,0 +1 @@
+(-2) ** 1;
diff --git a/test/fixtures/ES2016/exponent/exp_paren.tree.json b/test/fixtures/ES2016/exponent/exp_paren.tree.json
@@ -0,0 +1,240 @@
+{
+    "type": "Program",
+    "body": [
+        {
+            "type": "ExpressionStatement",
+            "expression": {
+                "type": "BinaryExpression",
+                "operator": "**",
+                "left": {
+                    "type": "UnaryExpression",
+                    "operator": "-",
+                    "argument": {
+                        "type": "Literal",
+                        "value": 2,
+                        "raw": "2",
+                        "range": [
+                            2,
+                            3
+                        ],
+                        "loc": {
+                            "start": {
+                                "line": 1,
+                                "column": 2
+                            },
+                            "end": {
+                                "line": 1,
+                                "column": 3
+                            }
+                        }
+                    },
+                    "prefix": true,
+                    "range": [
+                        1,
+                        3
+                    ],
+                    "loc": {
+                        "start": {
+                            "line": 1,
+                            "column": 1
+                        },
+                        "end": {
+                            "line": 1,
+                            "column": 3
+                        }
+                    }
+                },
+                "right": {
+                    "type": "Literal",
+                    "value": 1,
+                    "raw": "1",
+                    "range": [
+                        8,
+                        9
+                    ],
+                    "loc": {
+                        "start": {
+                            "line": 1,
+                            "column": 8
+                        },
+                        "end": {
+                            "line": 1,
+                            "column": 9
+                        }
+                    }
+                },
+                "range": [
+                    0,
+                    9
+                ],
+                "loc": {
+                    "start": {
+                        "line": 1,
+                        "column": 0
+                    },
+                    "end": {
+                        "line": 1,
+                        "column": 9
+                    }
+                }
+            },
+            "range": [
+                0,
+                10
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 0
+                },
+                "end": {
+                    "line": 1,
+                    "column": 10
+                }
+            }
+        }
+    ],
+    "sourceType": "script",
+    "range": [
+        0,
+        10
+    ],
+    "loc": {
+        "start": {
+            "line": 1,
+            "column": 0
+        },
+        "end": {
+            "line": 1,
+            "column": 10
+        }
+    },
+    "tokens": [
+        {
+            "type": "Punctuator",
+            "value": "(",
+            "range": [
+                0,
+                1
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 0
+                },
+                "end": {
+                    "line": 1,
+                    "column": 1
+                }
+            }
+        },
+        {
+            "type": "Punctuator",
+            "value": "-",
+            "range": [
+                1,
+                2
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 1
+                },
+                "end": {
+                    "line": 1,
+                    "column": 2
+                }
+            }
+        },
+        {
+            "type": "Numeric",
+            "value": "2",
+            "range": [
+                2,
+                3
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 2
+                },
+                "end": {
+                    "line": 1,
+                    "column": 3
+                }
+            }
+        },
+        {
+            "type": "Punctuator",
+            "value": ")",
+            "range": [
+                3,
+                4
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 3
+                },
+                "end": {
+                    "line": 1,
+                    "column": 4
+                }
+            }
+        },
+        {
+            "type": "Punctuator",
+            "value": "**",
+            "range": [
+                5,
+                7
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 5
+                },
+                "end": {
+                    "line": 1,
+                    "column": 7
+                }
+            }
+        },
+        {
+            "type": "Numeric",
+            "value": "1",
+            "range": [
+                8,
+                9
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 8
+                },
+                "end": {
+                    "line": 1,
+                    "column": 9
+                }
+            }
+        },
+        {
+            "type": "Punctuator",
+            "value": ";",
+            "range": [
+                9,
+                10
+            ],
+            "loc": {
+                "start": {
+                    "line": 1,
+                    "column": 9
+                },
+                "end": {
+                    "line": 1,
+                    "column": 10
+                }
+            }
+        }
+    ]
+}