PY-81646 Get rid of EMPTY_EXPRESSION nodes within SLICE_ITEM

GitOrigin-RevId: 6ffe0027790bb41b8ac18251903529aa1b1243f6

python/python-ast/src/com/jetbrains/python/ast/PyAstSliceItem.java

@@ -1,7 +1,9 @@
 // Copyright 2000-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.jetbrains.python.ast;
 
-import com.jetbrains.python.PythonDialectsTokenSetProvider;
+import com.intellij.lang.ASTNode;
+import com.intellij.psi.tree.TokenSet;
+import com.jetbrains.python.PyTokenTypes;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
 
@@ -9,14 +11,32 @@ import org.jetbrains.annotations.Nullable;
 @ApiStatus.Experimental
 public interface PyAstSliceItem extends PyAstExpression {
   default @Nullable PyAstExpression getLowerBound() {
-    return childToPsi(PythonDialectsTokenSetProvider.getInstance().getExpressionTokens(), 0);
+    return getChildExpression(0);
   }
 
   default @Nullable PyAstExpression getUpperBound() {
-    return childToPsi(PythonDialectsTokenSetProvider.getInstance().getExpressionTokens(), 1);
+    return getChildExpression(1);
   }
 
   default @Nullable PyAstExpression getStride() {
-    return childToPsi(PythonDialectsTokenSetProvider.getInstance().getExpressionTokens(), 2);
+    return getChildExpression(2);
+  }
+
+  private @Nullable PyAstExpression getChildExpression(int index) {
+    ASTNode[] children = getNode().getChildren(TokenSet.ANY);
+    int i = 0;
+    while (i < children.length && index > 0) {
+      if (children[i].getElementType() == PyTokenTypes.COLON) {
+        i++;
+      }
+      else {
+        i += 2;
+      }
+      index--;
+    }
+    if (i < children.length && children[i].getElementType() != PyTokenTypes.COLON) {
+      return (PyAstExpression)children[i].getPsi();
+    }
+    return null;
   }
 }

python/python-parser/src/com/jetbrains/python/parsing/ExpressionParsing.java

@@ -693,18 +693,13 @@ public class ExpressionParsing extends Parsing {
 
   private boolean parseSubscriptionIndexArgument() {
     SyntaxTreeBuilder.Marker sliceItem = myBuilder.mark();
-    if (!parseSingleExpression(false)) {
-      myBuilder.mark().done(PyElementTypes.EMPTY_EXPRESSION);
-    }
+    parseSingleExpression(false);
     if (!matchToken(PyTokenTypes.COLON)) {
       sliceItem.rollbackTo();
       return parseNamedTestExpression(false, false);
     }
-    boolean exprParseResult = parseSingleExpression(false);
+    parseSingleExpression(false);
     if (myBuilder.getTokenType() == PyTokenTypes.COLON) {
-      if (!exprParseResult) {
-        myBuilder.mark().done(PyElementTypes.EMPTY_EXPRESSION);
-      }
       myBuilder.advanceLexer();
       parseSingleExpression(false);
     }

python/testData/psi/ExtendedSlices.txt

@@ -5,11 +5,7 @@ PyFile:ExtendedSlices.py
         PsiElement(Py:IDENTIFIER)('d')
       PsiElement(Py:LBRACKET)('[')
       PySliceItem
-        PyEmptyExpression
-          <empty list>
         PsiElement(Py:COLON)(':')
-        PyEmptyExpression
-          <empty list>
         PsiElement(Py:COLON)(':')
       PsiElement(Py:RBRACKET)(']')
   PsiWhiteSpace('\n')
@@ -22,8 +18,6 @@ PyFile:ExtendedSlices.py
         PyNumericLiteralExpression
           PsiElement(Py:INTEGER_LITERAL)('1')
         PsiElement(Py:COLON)(':')
-        PyEmptyExpression
-          <empty list>
         PsiElement(Py:COLON)(':')
         PyNumericLiteralExpression
           PsiElement(Py:INTEGER_LITERAL)('2')
@@ -94,8 +88,6 @@ PyFile:ExtendedSlices.py
       PsiElement(Py:LBRACKET)('[')
       PyTupleExpression
         PySliceItem
-          PyEmptyExpression
-            <empty list>
           PsiElement(Py:COLON)(':')
           PyNumericLiteralExpression
             PsiElement(Py:INTEGER_LITERAL)('42')
@@ -108,8 +100,6 @@ PyFile:ExtendedSlices.py
         PsiElement(Py:COMMA)(',')
         PsiWhiteSpace(' ')
         PySliceItem
-          PyEmptyExpression
-            <empty list>
           PsiElement(Py:COLON)(':')
           PyNumericLiteralExpression
             PsiElement(Py:INTEGER_LITERAL)('24')

python/testData/psi/RangeAsLHS.txt

@@ -15,8 +15,6 @@ PyFile:RangeAsLHS.py
         PsiElement(Py:IDENTIFIER)('foo')
       PsiElement(Py:LBRACKET)('[')
       PySliceItem
-        PyEmptyExpression
-          <empty list>
         PsiElement(Py:COLON)(':')
       PsiElement(Py:RBRACKET)(']')
     PsiWhiteSpace(' ')

python/testData/psi/SliceList.txt

@@ -9,7 +9,5 @@ PyFile:SliceList.py
           PsiElement(Py:IDENTIFIER)('b1')
         PsiElement(Py:COMMA)(',')
         PySliceItem
-          PyEmptyExpression
-            <empty list>
           PsiElement(Py:COLON)(':')
       PsiElement(Py:RBRACKET)(']')