Reject identifier or keyword immediately following a numeric literal

src/diagnosticMessages.generated.ts

@@ -116,6 +116,7 @@ export enum DiagnosticCode {
   A_definite_assignment_assertion_is_not_permitted_in_this_context = 1255,
   A_class_may_only_extend_another_class = 1311,
   A_parameter_property_cannot_be_declared_using_a_rest_parameter = 1317,
+  An_identifier_or_keyword_cannot_immediately_follow_a_numeric_literal = 1351,
   Duplicate_identifier_0 = 2300,
   Cannot_find_name_0 = 2304,
   Module_0_has_no_exported_member_1 = 2305,
@@ -295,6 +296,7 @@ export function diagnosticCodeToString(code: DiagnosticCode): string {
     case 1255: return "A definite assignment assertion '!' is not permitted in this context.";
     case 1311: return "A class may only extend another class.";
     case 1317: return "A parameter property cannot be declared using a rest parameter.";
+    case 1351: return "An identifier or keyword cannot immediately follow a numeric literal.";
     case 2300: return "Duplicate identifier '{0}'.";
     case 2304: return "Cannot find name '{0}'.";
     case 2305: return "Module '{0}' has no exported member '{1}'.";

src/diagnosticMessages.json

@@ -111,6 +111,7 @@
   "A definite assignment assertion '!' is not permitted in this context.": 1255,
   "A class may only extend another class.": 1311,
   "A parameter property cannot be declared using a rest parameter.": 1317,
+  "An identifier or keyword cannot immediately follow a numeric literal.": 1351,
 
   "Duplicate identifier '{0}'.": 2300,
   "Cannot find name '{0}'.": 2304,

src/parser.ts

@@ -3800,10 +3800,14 @@ export class Parser extends DiagnosticEmitter {
         return Node.createStringLiteralExpression(tn.readString(), tn.range(startPos, tn.pos));
       }
       case Token.INTEGERLITERAL: {
-        return Node.createIntegerLiteralExpression(tn.readInteger(), tn.range(startPos, tn.pos));
+        let value = tn.readInteger();
+        tn.checkForIdentifierStartAfterNumericLiteral();
+        return Node.createIntegerLiteralExpression(value, tn.range(startPos, tn.pos));
       }
       case Token.FLOATLITERAL: {
-        return Node.createFloatLiteralExpression(tn.readFloat(), tn.range(startPos, tn.pos));
+        let value = tn.readFloat();
+        tn.checkForIdentifierStartAfterNumericLiteral();
+        return Node.createFloatLiteralExpression(value, tn.range(startPos, tn.pos));
       }
       // RegexpLiteralExpression
       // note that this also continues on invalid ones so the surrounding AST remains intact
@@ -4207,10 +4211,12 @@ export class Parser extends DiagnosticEmitter {
         }
         case Token.INTEGERLITERAL: {
           tn.readInteger();
+          tn.checkForIdentifierStartAfterNumericLiteral();
           break;
         }
         case Token.FLOATLITERAL: {
           tn.readFloat();
+          tn.checkForIdentifierStartAfterNumericLiteral();
           break;
         }
         case Token.OPENBRACE: {
@@ -4255,10 +4261,12 @@ export class Parser extends DiagnosticEmitter {
         }
         case Token.INTEGERLITERAL: {
           tn.readInteger();
+          tn.checkForIdentifierStartAfterNumericLiteral();
           break;
         }
         case Token.FLOATLITERAL: {
           tn.readFloat();
+          tn.checkForIdentifierStartAfterNumericLiteral();
           break;
         }
       }

src/tokenizer.ts

@@ -1611,6 +1611,17 @@ export class Tokenizer extends DiagnosticEmitter {
     return String.fromCharCode(value);
   }
 
+  checkForIdentifierStartAfterNumericLiteral(): void {
+    // TODO: BigInt n
+    var pos = this.pos;
+    if (pos < this.end && isIdentifierStart(this.source.text.charCodeAt(pos))) {
+      this.error(
+        DiagnosticCode.An_identifier_or_keyword_cannot_immediately_follow_a_numeric_literal,
+        this.range(pos)
+      );
+    }
+  }
+
   readUnicodeEscape(): string {
     return this.readHexadecimalEscape(4);
   }

tests/parser/literals.ts

@@ -60,3 +60,19 @@
 "1\"23";
 "1\"2\\3";
 "\0\n\\n\r";
+
+// invalid
+1..;
+3u8;
+4b;
+5-;
+6=;
+7_;
+1.a;
+2.0b;
+
+// technically invalid, but not handled by AS yet, TS1005: ';' expected
+3 4;
+5 c;
+6.7 d;
+a b;

tests/parser/literals.ts.fixture.ts

@@ -60,3 +60,25 @@
 "1\"23";
 "1\"2\\3";
 "\0\n\\n\r";
+4;
+b;
+7;
+1;
+a;
+2;
+b;
+3;
+4;
+5;
+c;
+6.7;
+d;
+a;
+b;
+// ERROR 1109: "Expression expected." in literals.ts(65,4+1)
+// ERROR 1351: "An identifier or keyword cannot immediately follow a numeric literal." in literals.ts(66,2+0)
+// ERROR 1351: "An identifier or keyword cannot immediately follow a numeric literal." in literals.ts(67,2+0)
+// ERROR 1109: "Expression expected." in literals.ts(68,3+1)
+// ERROR 6188: "Numeric separators are not allowed here." in literals.ts(70,2+0)
+// ERROR 1351: "An identifier or keyword cannot immediately follow a numeric literal." in literals.ts(71,3+0)
+// ERROR 1351: "An identifier or keyword cannot immediately follow a numeric literal." in literals.ts(72,4+0)