for..of no longer requires a variable qualifier

Addresses wcjohnson/lightscript#38
wcjohnson · Oct 8, 2017 · 19b141c · 19b141c
1 parent 95c3353
commit 19b141c
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Showing 11 changed files with 274 additions and 26 deletions.
diff --git a/src/parser/statement.js b/src/parser/statement.js
@@ -336,6 +336,30 @@ pp.parseForStatement = function (node) {
     return this.parseFor(node, null);
   }
 
+  if (this.hasPlugin("lightscript") && (!forAwait)) {
+    // idx, elem, key, or val begins a LS-enhanced loop.
+    if (
+      this.isContextual("idx") ||
+      this.isContextual("elem") ||
+      this.isContextual("key") ||
+      this.isContextual("val")
+    ) {
+      // Disambiguate between:
+      // for idx of e: body
+      // for idx of in e: body
+      // for idx of, elem x in e: body
+      //
+      // If next isn't "of", or next+1 is "in" or ",", then it's a for-in
+      const nextTwo = this.tokenLookahead(2);
+      if (
+        (!(nextTwo[0] === tt.name && nextTwo[1] === "of")) || // next isnt of
+        (nextTwo[2] === tt._in || nextTwo[2] === tt.comma) // next+1 is "in" or ","
+      ) {
+        return this.parseEnhancedForIn(node);
+      }
+    }
+  }
+
   if (this.match(tt._var) || this.match(tt._let) || this.match(tt._const)) {
     const init = this.startNode();
     const varKind = this.state.type;
@@ -354,23 +378,12 @@ pp.parseForStatement = function (node) {
     return this.parseFor(node, init);
   }
 
-  if (this.hasPlugin("lightscript") && (!forAwait)) {
-    // idx, elem, key, or val begins a LS-enhanced loop.
-    if (
-      (this.isContextual("idx") || this.isContextual("elem") || this.isContextual("key") || this.isContextual("val"))
-    ) {
-      return this.parseEnhancedForIn(node);
-    }
-  }
-
   const refShorthandDefaultPos = { start: 0 };
   const init = this.parseExpression(true, refShorthandDefaultPos);
   if (this.match(tt._in) || this.isContextual("of")) {
     if (this.hasPlugin("lightscript") && (!init.isNowAssign)) {
       if (this.match(tt._in)) {
         this.raise(this.state.lastTokStart, "for-in requires a variable qualifier: `now` to reassign an existing variable, or `const`, `let`, `var` to declare a new one. Use `idx` or `elem` to iterate an array. Use `key` or `val` to iterate an object.");
-      } else {
-        this.raise(this.state.lastTokStart, "for-of requires a variable qualifier: `now` to reassign an existing variable, or `const`, `let`, `var` to declare a new one.");
       }
     }
 

diff --git a/src/tokenizer/index.js b/src/tokenizer/index.js
@@ -97,6 +97,24 @@ export default class Tokenizer {
     return curr;
   }
 
+  tokenLookahead(n) {
+    const result = [];
+
+    const old = this.state;
+    this.state = old.clone(true);
+
+    this.isLookahead = true;
+    while (n > 0) {
+      this.next();
+      result.push(this.state.type, this.state.value);
+      n--;
+    }
+    this.isLookahead = false;
+
+    this.state = old;
+    return result;
+  }
+
   // Toggle strict mode. Re-reads the next number or string to please
   // pedantic tests (`"use strict"; 010;` should fail).
 

diff --git a/test/fixtures/es2015/uncategorised/107/options.lightscript.json b/test/fixtures/es2015/uncategorised/107/options.lightscript.json
diff --git a/test/fixtures/esprima/es2015-for-of/for-of-array-pattern/options.lightscript.json b/test/fixtures/esprima/es2015-for-of/for-of-array-pattern/options.lightscript.json
diff --git a/test/fixtures/esprima/es2015-for-of/for-of-object-pattern/options.lightscript.json b/test/fixtures/esprima/es2015-for-of/for-of-object-pattern/options.lightscript.json
diff --git a/test/fixtures/esprima/es2015-for-of/for-of/options.lightscript.json b/test/fixtures/esprima/es2015-for-of/for-of/options.lightscript.json
diff --git a/test/fixtures/esprima/es2015-for-of/invalid-lhs-init/options.lightscript.json b/test/fixtures/esprima/es2015-for-of/invalid-lhs-init/options.lightscript.json
diff --git a/test/fixtures/lightscript/for-in/like-for-of/actual.js b/test/fixtures/lightscript/for-in/like-for-of/actual.js
@@ -0,0 +1 @@
+for elem of in arr: of
diff --git a/test/fixtures/lightscript/for-in/like-for-of/expected.json b/test/fixtures/lightscript/for-in/like-for-of/expected.json
@@ -0,0 +1,115 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 22,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 22
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 22,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 22
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ForInArrayStatement",
+        "start": 0,
+        "end": 22,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 22
+          }
+        },
+        "elem": {
+          "type": "Identifier",
+          "start": 9,
+          "end": 11,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 9
+            },
+            "end": {
+              "line": 1,
+              "column": 11
+            },
+            "identifierName": "of"
+          },
+          "name": "of"
+        },
+        "body": {
+          "type": "ExpressionStatement",
+          "start": 20,
+          "end": 22,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 20
+            },
+            "end": {
+              "line": 1,
+              "column": 22
+            }
+          },
+          "expression": {
+            "type": "Identifier",
+            "start": 20,
+            "end": 22,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 20
+              },
+              "end": {
+                "line": 1,
+                "column": 22
+              },
+              "identifierName": "of"
+            },
+            "name": "of"
+          }
+        },
+        "array": {
+          "type": "Identifier",
+          "start": 15,
+          "end": 18,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 15
+            },
+            "end": {
+              "line": 1,
+              "column": 18
+            },
+            "identifierName": "arr"
+          },
+          "name": "arr"
+        }
+      }
+    ],
+    "directives": []
+  }
+}
diff --git a/test/fixtures/lightscript/for-of/like-enhanced-for-in/actual.js b/test/fixtures/lightscript/for-of/like-enhanced-for-in/actual.js
@@ -0,0 +1 @@
+for elem of elems: elem
diff --git a/test/fixtures/lightscript/for-of/like-enhanced-for-in/expected.json b/test/fixtures/lightscript/for-of/like-enhanced-for-in/expected.json
@@ -0,0 +1,115 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 23,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 23
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 23,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 23
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ForOfStatement",
+        "start": 0,
+        "end": 23,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 23
+          }
+        },
+        "left": {
+          "type": "Identifier",
+          "start": 4,
+          "end": 8,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 4
+            },
+            "end": {
+              "line": 1,
+              "column": 8
+            },
+            "identifierName": "elem"
+          },
+          "name": "elem"
+        },
+        "right": {
+          "type": "Identifier",
+          "start": 12,
+          "end": 17,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 12
+            },
+            "end": {
+              "line": 1,
+              "column": 17
+            },
+            "identifierName": "elems"
+          },
+          "name": "elems"
+        },
+        "body": {
+          "type": "ExpressionStatement",
+          "start": 19,
+          "end": 23,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 19
+            },
+            "end": {
+              "line": 1,
+              "column": 23
+            }
+          },
+          "expression": {
+            "type": "Identifier",
+            "start": 19,
+            "end": 23,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 19
+              },
+              "end": {
+                "line": 1,
+                "column": 23
+              },
+              "identifierName": "elem"
+            },
+            "name": "elem"
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}