Improved errors for if:

Author: Tobias-Kohn

tpParser/shared/src/main/scala/tigerpython/parser/parsing/ExpressionParser.scala

@@ -410,7 +410,18 @@ class ExpressionParser(val parser: Parser, val parserState: ParserState) {
     while (tokens.hasType(TokenType.EQ, TokenType.NEQ, TokenType.IS, TokenType.IS_NOT,
       TokenType.LEQ, TokenType.LESS, TokenType.IN, TokenType.NOT_IN,
       TokenType.GEQ, TokenType.GREATER)) {
-      val op = BinOp.fromTokenType(tokens.next().tokenType)
+      val op: BinOp.Value =
+        if (tokens.hasType(TokenType.IS, TokenType.IS_NOT) && tokens.peekType(1) == TokenType.IN) {
+          val invert = tokens.headType == TokenType.IS_NOT
+          parserState.reportError(tokens.pos, ErrorCode.EXTRA_TOKEN, "is")
+          tokens.next()
+          tokens.next()
+          if (invert)
+            BinOp.CMP_NOT_IN
+          else
+            BinOp.CMP_IN
+        } else
+          BinOp.fromTokenType(tokens.next().tokenType)
       result += ((op, parseExpr(tokens)))
     }
     if (result.nonEmpty)
@@ -763,7 +774,7 @@ class ExpressionParser(val parser: Parser, val parserState: ParserState) {
     val test =
       if (tokens.headType == TokenType.COMMA) {
         parserState.reportError(tokens, ErrorCode.MISSING_EXPRESSION)
-        null
+        AstNode.EmptyExpression(tokens.pos)
       } else
         parseTest(tokens)
     if (tokens.hasType(TokenType.FOR)) {

tpParser/shared/src/main/scala/tigerpython/parser/parsing/Parser.scala

@@ -1233,8 +1233,14 @@ class Parser(val source: CharSequence,
     val tokens = line.tokenSource
     tokens.next()
     val test = if (tokens.hasType(TokenType.COLON)) {
-      parserState.reportError(tokens.pos, ErrorCode.MISSING_COMPARISON)
-      AstNode.EmptyExpression(tokens.pos)
+      if (tokens.remaining > 1 && expressionParser.firstOfTest(tokens.peek(1)) && (tokens.hasColonAtEnd || line.hasSuite)) {
+        parserState.reportError(tokens.pos, ErrorCode.EXTRA_TOKEN, ":")
+        tokens.next()
+        expressionParser.parseCmpTest(tokens)
+      } else {
+        parserState.reportError(tokens.pos, ErrorCode.MISSING_COMPARISON)
+        AstNode.EmptyExpression(tokens.pos)
+      }
     } else
       expressionParser.parseCmpTest(tokens)
     if (tokens.hasNext && tokens.head.tokenType != TokenType.COLON && line.hasSuite && tokens.hasColonAtEnd) {

tpParser/shared/src/test/programs/erroneous/conditionals_01.txt

@@ -0,0 +1,4 @@
+# 1
+# MISSING_COMPARISON
+if:
+    pass

tpParser/shared/src/test/programs/erroneous/conditionals_02.txt

@@ -0,0 +1,4 @@
+# 1
+# EXTRA_TOKEN
+if: x < 5:
+    print(x)

tpParser/shared/src/test/scala/DebugTester.scala

@@ -14,9 +14,8 @@ class DebugTester extends FunSuite  {
   }
 
   private val PROGRAM: String =
-    """my_list = [,,,]
-      |
-      |print(my_list)
+    """if:
+      |     pass
       |""".stripMargin
 
   {