SafeMemberExpression

src/parser/expression.js

@@ -348,6 +348,23 @@ pp.parseSubscripts = function (base, startPos, startLoc, noCalls) {
       node.property = this.parseIdentifier(true);
       node.computed = false;
       base = this.finishNode(node, "MemberExpression");
+    } else if (this.hasPlugin("lightscript") && this.match(tt.elvis)) {
+      // `x?.y`
+      const node = this.startNodeAt(startPos, startLoc);
+      const op = this.state.value;
+      this.next();
+      node.object = base;
+      if (op === "?.") {
+        node.property = this.parseIdentifier(true);
+        node.computed = false;
+      } else if (op === "?[") {
+        node.property = this.parseExpression();
+        node.computed = true;
+        this.expect(tt.bracketR);
+      } else {
+        this.unexpected();
+      }
+      base = this.finishNode(node, "SafeMemberExpression");
     } else if (this.hasPlugin("lightscript") && !noCalls && this.eat(tt.tilde)) {
       const node = this.startNodeAt(startPos, startLoc);
       node.left = base;

src/plugins/lightscript.js

@@ -450,7 +450,8 @@ pp.parseAwaitArrow = function (left) {
 };
 
 pp.tryParseNamedArrowDeclaration = function () {
-  let node = this.startNode(), call = this.startNode();
+  let node = this.startNode();
+  const call = this.startNode();
 
   if (!this.match(tt.name)) return null;
   if (this.state.value === "type") return null;

src/tokenizer/index.js

@@ -523,7 +523,16 @@ export default class Tokenizer {
           return this.finishToken(tt.colon);
         }
 
-      case 63: ++this.state.pos; return this.finishToken(tt.question);
+      case 63:
+        if (this.hasPlugin("lightscript")) {
+          const next = this.input.charCodeAt(this.state.pos + 1);
+          // `?.` or `?[`
+          if (next === 46 || next === 91) {
+            return this.finishOp(tt.elvis, 2);
+          }
+        }
+        ++this.state.pos;
+        return this.finishToken(tt.question);
       case 64: ++this.state.pos; return this.finishToken(tt.at);
 
       case 96: // '`'

src/tokenizer/types.js

@@ -58,6 +58,7 @@ export const types = {
   colonEq: new TokenType(":=", { beforeExpr, isAssign }),
   tilde: new TokenType("~"),
   awaitArrow: new TokenType("<-", { beforeExpr, isAssign }),
+  elvis: new TokenType("?."),
 
   num: new TokenType("num", { startsExpr }),
   regexp: new TokenType("regexp", { startsExpr }),

test/fixtures/lightscript/safe-member-expression/basic/actual.js

@@ -0,0 +1 @@
+x?.y

test/fixtures/lightscript/safe-member-expression/basic/expected.json

@@ -0,0 +1,99 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 4,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 4
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 4,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 4
+      }
+    },
+    "sourceType": "script",
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 4,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 4
+          }
+        },
+        "expression": {
+          "type": "SafeMemberExpression",
+          "start": 0,
+          "end": 4,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 0
+            },
+            "end": {
+              "line": 1,
+              "column": 4
+            }
+          },
+          "object": {
+            "type": "Identifier",
+            "start": 0,
+            "end": 1,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 0
+              },
+              "end": {
+                "line": 1,
+                "column": 1
+              },
+              "identifierName": "x"
+            },
+            "name": "x"
+          },
+          "property": {
+            "type": "Identifier",
+            "start": 3,
+            "end": 4,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 3
+              },
+              "end": {
+                "line": 1,
+                "column": 4
+              },
+              "identifierName": "y"
+            },
+            "name": "y"
+          },
+          "computed": false
+        }
+      }
+    ],
+    "directives": []
+  }
+}

test/fixtures/lightscript/safe-member-expression/chained/actual.js

@@ -0,0 +1 @@
+x.y?.a?.b.c[d](e, f)[g]?.h