fix: Support separating interface members with commas (#1375)

Author: MaxGraey

Diff for: src/parser.ts

@@ -2169,7 +2169,7 @@ export class Parser extends DiagnosticEmitter {
             tn.range()
           );
         }
-        returnType = this.parseType(tn, name.kind == NodeKind.CONSTRUCTOR || isSetter);
+        returnType = this.parseType(tn, isSetter || name.kind == NodeKind.CONSTRUCTOR);
         if (!returnType) return null;
       } else {
         returnType = Node.createOmittedType(tn.range(tn.pos));
@@ -2209,7 +2209,7 @@ export class Parser extends DiagnosticEmitter {
         }
         body = this.parseBlockStatement(tn, false);
         if (!body) return null;
-      } else if (!(flags & (CommonFlags.AMBIENT | CommonFlags.ABSTRACT)) && !isInterface) {
+      } else if (!isInterface && !(flags & (CommonFlags.AMBIENT | CommonFlags.ABSTRACT))) {
         this.error(
           DiagnosticCode.Function_implementation_is_missing_or_not_immediately_following_the_declaration,
           tn.range()
@@ -2225,7 +2225,9 @@ export class Parser extends DiagnosticEmitter {
         body,
         tn.range(startPos, tn.pos)
       );
-      tn.skip(Token.SEMICOLON);
+      if (!(isInterface && tn.skip(Token.COMMA))) {
+        tn.skip(Token.SEMICOLON);
+      }
       return retMethod;
 
     } else if (isConstructor) {
@@ -2288,7 +2290,10 @@ export class Parser extends DiagnosticEmitter {
         if (!initializer) return null;
       }
       let range = tn.range(startPos, tn.pos);
-      if ((flags & CommonFlags.DEFINITELY_ASSIGNED) != 0 && ((flags & CommonFlags.STATIC) != 0 || isInterface || initializer !== null)) {
+      if (
+        (flags & CommonFlags.DEFINITELY_ASSIGNED) != 0 &&
+        (isInterface || initializer !== null || (flags & CommonFlags.STATIC) != 0)
+      ) {
         this.error(
           DiagnosticCode.A_definite_assignment_assertion_is_not_permitted_in_this_context,
           range
@@ -2302,7 +2307,9 @@ export class Parser extends DiagnosticEmitter {
         initializer,
         range
       );
-      tn.skip(Token.SEMICOLON);
+      if (!(isInterface && tn.skip(Token.COMMA))) {
+        tn.skip(Token.SEMICOLON);
+      }
       return retField;
     }
     return null;

Diff for: tests/parser/interface.ts

@@ -3,3 +3,9 @@ interface Foo {
   baz: i32;
   readonly baz2: f64;
 }
+
+interface Boo {
+  bar(): void,
+  baz: i32,
+  readonly baz2: f64,
+}

Diff for: tests/parser/interface.ts.fixture.ts

@@ -3,3 +3,8 @@ interface Foo {
   baz: i32;
   readonly baz2: f64;
 }
+interface Boo {
+  bar(): void;
+  baz: i32;
+  readonly baz2: f64;
+}