improve parser recovery if keyword is used as function or class name (PY-8319)

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

@@ -44,12 +44,7 @@ public class FunctionParsing extends Parsing {
 
   protected void parseFunctionInnards(PsiBuilder.Marker functionMarker) {
     myBuilder.advanceLexer();
-    if (myBuilder.getTokenType() == PyTokenTypes.IDENTIFIER) {
-      myBuilder.advanceLexer();
-    }
-    else {
-      myBuilder.error(message("PARSE.expected.func.name"));
-    }
+    checkMatchesOrSkip(PyTokenTypes.IDENTIFIER, message("PARSE.expected.func.name"));
     parseParameterList();
     parseReturnTypeAnnotation();
     checkMatches(PyTokenTypes.COLON, message("PARSE.expected.colon"));

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

@@ -61,6 +61,17 @@ public class Parsing {
     return false;
   }
 
+  protected boolean checkMatchesOrSkip(final IElementType token, final String message) {
+    if (myBuilder.getTokenType() == token) {
+      myBuilder.advanceLexer();
+      return true;
+    }
+    PsiBuilder.Marker mark = myBuilder.mark();
+    myBuilder.advanceLexer();
+    mark.error(message);
+    return false;
+  }
+
   protected void assertCurrentToken(final PyElementType tokenType) {
     LOG.assertTrue(myBuilder.getTokenType() == tokenType);
   }

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

@@ -777,7 +777,7 @@ public class StatementParsing extends Parsing implements ITokenTypeRemapper {
   public void parseClassDeclaration(PsiBuilder.Marker classMarker, ParsingScope scope) {
     assertCurrentToken(PyTokenTypes.CLASS_KEYWORD);
     myBuilder.advanceLexer();
-    checkMatches(PyTokenTypes.IDENTIFIER, IDENTIFIER_EXPECTED);
+    checkMatchesOrSkip(PyTokenTypes.IDENTIFIER, IDENTIFIER_EXPECTED);
     if (myBuilder.getTokenType() == PyTokenTypes.LPAR) {
       getExpressionParser().parseArgumentList();
     }

python/testData/psi/KeywordAsClassName.py

@@ -0,0 +1,2 @@
+class from:
+    pass

python/testData/psi/KeywordAsClassName.txt

@@ -0,0 +1,13 @@
+PyFile:KeywordAsClassName.py
+  PyClass: null
+    PsiElement(Py:CLASS_KEYWORD)('class')
+    PsiWhiteSpace(' ')
+    PsiErrorElement:Identifier expected
+      PsiElement(Py:FROM_KEYWORD)('from')
+    PyArgumentList
+      <empty list>
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyPassStatement
+        PsiElement(Py:PASS_KEYWORD)('pass')

python/testData/psi/KeywordAsFunctionName.py

@@ -0,0 +1,2 @@
+def from():
+    pass

python/testData/psi/KeywordAsFunctionName.txt

@@ -0,0 +1,14 @@
+PyFile:KeywordAsFunctionName.py
+  PyFunction('null')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiErrorElement:function name expected
+      PsiElement(Py:FROM_KEYWORD)('from')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyPassStatement
+        PsiElement(Py:PASS_KEYWORD)('pass')

python/testSrc/com/jetbrains/python/PythonParsingTest.java

@@ -410,6 +410,14 @@ public class PythonParsingTest extends ParsingTestCase {
     doTest();
   }
 
+  public void testKeywordAsClassName() {  // PY-8319
+    doTest();
+  }
+
+  public void testKeywordAsFunctionName() {  // PY-8319
+    doTest();
+  }
+
   public void doTest(LanguageLevel languageLevel) {
     LanguageLevel prev = myLanguageLevel;
     myLanguageLevel = languageLevel;