fix: check preceding line break before exclamation (#14049)

JLHwung · web-flow · commit ad17fe1ccead · 2021-12-16T15:50:15.000-05:00
diff --git a/packages/babel-parser/src/plugins/typescript/index.js b/packages/babel-parser/src/plugins/typescript/index.js
@@ -2832,7 +2832,11 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       kind: "var" | "let" | "const",
     ): void {
       super.parseVarId(decl, kind);
-      if (decl.id.type === "Identifier" && this.eat(tt.bang)) {
+      if (
+        decl.id.type === "Identifier" &&
+        !this.hasPrecedingLineBreak() &&
+        this.eat(tt.bang)
+      ) {
         decl.definite = true;
       }
 
diff --git a/packages/babel-parser/test/fixtures/typescript/variable-declarator/definite-asi/input.ts b/packages/babel-parser/test/fixtures/typescript/variable-declarator/definite-asi/input.ts
@@ -0,0 +1,2 @@
+let x
+!function() {};
diff --git a/packages/babel-parser/test/fixtures/typescript/variable-declarator/definite-asi/output.json b/packages/babel-parser/test/fixtures/typescript/variable-declarator/definite-asi/output.json
@@ -0,0 +1,54 @@
+{
+  "type": "File",
+  "start":0,"end":21,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":15}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":21,"loc":{"start":{"line":1,"column":0},"end":{"line":2,"column":15}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "VariableDeclaration",
+        "start":0,"end":5,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":5}},
+        "declarations": [
+          {
+            "type": "VariableDeclarator",
+            "start":4,"end":5,"loc":{"start":{"line":1,"column":4},"end":{"line":1,"column":5}},
+            "id": {
+              "type": "Identifier",
+              "start":4,"end":5,"loc":{"start":{"line":1,"column":4},"end":{"line":1,"column":5},"identifierName":"x"},
+              "name": "x"
+            },
+            "init": null
+          }
+        ],
+        "kind": "let"
+      },
+      {
+        "type": "ExpressionStatement",
+        "start":6,"end":21,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":15}},
+        "expression": {
+          "type": "UnaryExpression",
+          "start":6,"end":20,"loc":{"start":{"line":2,"column":0},"end":{"line":2,"column":14}},
+          "operator": "!",
+          "prefix": true,
+          "argument": {
+            "type": "FunctionExpression",
+            "start":7,"end":20,"loc":{"start":{"line":2,"column":1},"end":{"line":2,"column":14}},
+            "id": null,
+            "generator": false,
+            "async": false,
+            "params": [],
+            "body": {
+              "type": "BlockStatement",
+              "start":18,"end":20,"loc":{"start":{"line":2,"column":12},"end":{"line":2,"column":14}},
+              "body": [],
+              "directives": []
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}
