Updated star expression annotator to allow * unpacking in tuples and lists

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

@@ -190,7 +190,7 @@ public class ExpressionParsing extends Parsing {
     }
 
     if (atToken(PyTokenTypes.EXP)) {
-      if (!parseStarExpression(false)) {
+      if (!parseDoubleStarExpression(false)) {
         myBuilder.error("expression expected");
         expr.done(PyElementTypes.DICT_LITERAL_EXPRESSION);
         return;
@@ -248,7 +248,7 @@ public class ExpressionParsing extends Parsing {
     while (myBuilder.getTokenType() != PyTokenTypes.RBRACE) {
       checkMatches(PyTokenTypes.COMMA, message("PARSE.expected.comma"));
       if (atToken(PyTokenTypes.EXP)) {
-        if (!parseStarExpression(false)) {
+        if (!parseDoubleStarExpression(false)) {
           break;
         }
       }
@@ -789,8 +789,7 @@ public class ExpressionParsing extends Parsing {
   }
 
   private boolean parseStarExpression(boolean isTargetExpression) {
-    final IElementType tokenType = myBuilder.getTokenType();
-    if (tokenType == PyTokenTypes.MULT || tokenType == PyTokenTypes.EXP) {
+    if (atToken(PyTokenTypes.MULT)) {
       PsiBuilder.Marker starExpr = myBuilder.mark();
       nextToken();
       if (!parseBitwiseORExpression(isTargetExpression)) {
@@ -798,7 +797,22 @@ public class ExpressionParsing extends Parsing {
         starExpr.drop();
         return false;
       }
-      starExpr.done(tokenType == PyTokenTypes.MULT ? PyElementTypes.STAR_EXPRESSION : PyElementTypes.DOUBLE_STAR_EXPRESSION);
+      starExpr.done(PyElementTypes.STAR_EXPRESSION);
+      return true;
+    }
+    return parseBitwiseORExpression(isTargetExpression);
+  }
+
+  private boolean parseDoubleStarExpression(boolean isTargetExpression) {
+    if (atToken(PyTokenTypes.EXP)) {
+      PsiBuilder.Marker starExpr = myBuilder.mark();
+      nextToken();
+      if (!parseBitwiseORExpression(isTargetExpression)) {
+        myBuilder.error(message("PARSE.expected.expression"));
+        starExpr.drop();
+        return false;
+      }
+      starExpr.done(PyElementTypes.DOUBLE_STAR_EXPRESSION);
       return true;
     }
     return parseBitwiseORExpression(isTargetExpression);

python/src/com/jetbrains/python/validation/StarAnnotator.java

@@ -15,8 +15,9 @@
  */
 package com.jetbrains.python.validation;
 
-import com.jetbrains.python.psi.PyStarExpression;
-import com.jetbrains.python.psi.PyTargetExpression;
+import com.intellij.psi.PsiElement;
+import com.jetbrains.python.psi.*;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * @author yole
@@ -25,8 +26,20 @@ public class StarAnnotator extends PyAnnotator {
   @Override
   public void visitPyStarExpression(PyStarExpression node) {
     super.visitPyStarExpression(node);
-    if (!(node.getExpression() instanceof PyTargetExpression)) {
-      getHolder().createErrorAnnotation(node, "can use starred expression only as assignment target");
+    if (!isAssignmentTarget(node) && !isStarUnpacking(node)) {
+      getHolder().createErrorAnnotation(node, "Can't use starred expression here");
     }
   }
+
+  private static boolean isStarUnpacking(@NotNull PyStarExpression node) {
+    PsiElement parent = node.getParent();
+    while (parent instanceof PyParenthesizedExpression) {
+      parent = parent.getParent();
+    }
+    return parent instanceof PyTupleExpression || parent instanceof PyListLiteralExpression;
+  }
+
+  private static boolean isAssignmentTarget(@NotNull PyStarExpression node) {
+    return node.getExpression() instanceof PyTargetExpression;
+  }
 }

python/testData/highlighting/starInGenerator.py

@@ -1 +1 @@
-y = (<error descr="can use starred expression only as assignment target">*()</error> for _ in ())
+y = (<error descr="Can't use starred expression here">*()</error> for _ in ())

python/testData/highlighting/unpackingStar.py

@@ -0,0 +1,9 @@
+1, *x
+(1, *x)
+[1, *x]
+
+if <error descr="Can't use starred expression here">*x</error>:
+    pass
+
+1 + (<error descr="Can't use starred expression here">*x</error>)
+1 + (*x,)

python/testSrc/com/jetbrains/python/PythonHighlightingTest.java

@@ -241,6 +241,10 @@ public class PythonHighlightingTest extends PyTestCase {
     doTest(LanguageLevel.PYTHON35, false, false);
   }
 
+  public void testUnpackingStar() {
+    doTest(LanguageLevel.PYTHON35, false, false);
+  }
+
   // ---
   private void doTest(final LanguageLevel languageLevel, final boolean checkWarnings, final boolean checkInfos) {
     PythonLanguageLevelPusher.setForcedLanguageLevel(myFixture.getProject(), languageLevel);