PY-21175 Add implicit negative type assertion after "if" in CFG unconditionally

The check that we should add such synthetic node only if there were no
pending edges inside the body of if statement (e.g. if it contained only
break/continue/return for the enclosing loop) seems doubtful and
doesn't cover the simplest/most common cases.

python/src/com/jetbrains/python/codeInsight/controlflow/PyControlFlowBuilder.java

@@ -365,13 +365,6 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
       });
       myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
     }
-    final Ref<Boolean> pendingInScopeEdges = Ref.create(false);
-    myBuilder.processPending((pendingScope, instruction) -> {
-      if (pendingScope != null && PsiTreeUtil.isAncestor(node, pendingScope, false)) {
-        pendingInScopeEdges.set(true);
-      }
-      myBuilder.addPendingEdge(pendingScope, instruction);
-    });
     final PyTypeAssertionEvaluator negativeAssertionEvaluator = new PyTypeAssertionEvaluator(false);
     final PyExpression ifCondition = ifPart.getCondition();
     // TODO: Add support for 'elif'
@@ -386,15 +379,11 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
       InstructionBuilder.addAssertInstructions(myBuilder, negativeAssertionEvaluator);
       elseBranch.accept(this);
       myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
-    } else {
-      if (!pendingInScopeEdges.get()) {
-        myBuilder.prevInstruction = lastBranchingPoint;
-        InstructionBuilder.addAssertInstructions(myBuilder, negativeAssertionEvaluator);
-        myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
-      }
-      else {
-        myBuilder.addPendingEdge(node, lastBranchingPoint);
-      }
+    }
+    else {
+      myBuilder.prevInstruction = lastBranchingPoint;
+      InstructionBuilder.addAssertInstructions(myBuilder, negativeAssertionEvaluator);
+      myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
     }
   }
 

python/testData/codeInsight/controlflow/implicitnegativetypeassertionafterif.py

@@ -0,0 +1,3 @@
+if xs is None:
+    xs = [1, 2, 3]
+print(xs)

python/testData/codeInsight/controlflow/implicitnegativetypeassertionafterif.txt

@@ -0,0 +1,12 @@
+0(1) element: null
+1(2) element: PyIfStatement
+2(3) READ ACCESS: xs
+3(4,8) READ ACCESS: None
+4(5) element: PyStatementList. Condition: xs is None:true
+5(6) ASSERTTYPE ACCESS: xs
+6(7) element: PyAssignmentStatement
+7(9) WRITE ACCESS: xs
+8(9) ASSERTTYPE ACCESS: xs
+9(10) element: PyPrintStatement
+10(11) READ ACCESS: xs
+11() element: null

python/testData/codeInsight/controlflow/implicitnegativetypeassertionaftertwonestedif.py

@@ -0,0 +1,5 @@
+if not isinstance(x, str):
+    if x is None:
+        print(x)
+    print(x)
+print(x)

python/testData/codeInsight/controlflow/implicitnegativetypeassertionaftertwonestedif.txt

@@ -0,0 +1,21 @@
+0(1) element: null
+1(2) element: PyIfStatement
+2(3) READ ACCESS: isinstance
+3(4) READ ACCESS: x
+4(5,17) READ ACCESS: str
+5(6) element: PyStatementList. Condition: not isinstance(x, str):true
+6(7) ASSERTTYPE ACCESS: x
+7(8) element: PyIfStatement
+8(9) READ ACCESS: x
+9(10,14) READ ACCESS: None
+10(11) element: PyStatementList. Condition: x is None:true
+11(12) ASSERTTYPE ACCESS: x
+12(13) element: PyPrintStatement
+13(15) READ ACCESS: x
+14(15) ASSERTTYPE ACCESS: x
+15(16) element: PyPrintStatement
+16(18) READ ACCESS: x
+17(18) ASSERTTYPE ACCESS: x
+18(19) element: PyPrintStatement
+19(20) READ ACCESS: x
+20() element: null

python/testData/codeInsight/controlflow/tryfinally.txt

@@ -6,23 +6,25 @@
 5(6,9) element: PyTryPart
 6(7,9) element: PyAssignmentStatement
 7(8,9) READ ACCESS: open
-8(9,17) WRITE ACCESS: status
+8(9,18) WRITE ACCESS: status
 9(10) element: PyFinallyPart
 10(11) element: PyIfStatement
 11(12) READ ACCESS: status
-12(13,27) READ ACCESS: None
+12(13,17) READ ACCESS: None
 13(14) element: PyStatementList. Condition: status is not None:true
 14(15) ASSERTTYPE ACCESS: status
 15(16) element: PyPrintStatement
-16(27) READ ACCESS: status
-17(18) element: PyFinallyPart
-18(19) element: PyIfStatement
-19(20) READ ACCESS: status
-20(21,25) READ ACCESS: None
-21(22) element: PyStatementList. Condition: status is not None:true
-22(23) ASSERTTYPE ACCESS: status
-23(24) element: PyPrintStatement
-24(25) READ ACCESS: status
-25(26) element: PyExpressionStatement
-26(27) READ ACCESS: status
-27() element: null
+16(29) READ ACCESS: status
+17(29) ASSERTTYPE ACCESS: status
+18(19) element: PyFinallyPart
+19(20) element: PyIfStatement
+20(21) READ ACCESS: status
+21(22,26) READ ACCESS: None
+22(23) element: PyStatementList. Condition: status is not None:true
+23(24) ASSERTTYPE ACCESS: status
+24(25) element: PyPrintStatement
+25(27) READ ACCESS: status
+26(27) ASSERTTYPE ACCESS: status
+27(28) element: PyExpressionStatement
+28(29) READ ACCESS: status
+29() element: null

python/testSrc/com/jetbrains/python/PyControlFlowBuilderTest.java

@@ -238,6 +238,16 @@ public class PyControlFlowBuilderTest extends LightMarkedTestCase {
     runWithLanguageLevel(LanguageLevel.PYTHON36, this::doTest);
   }
 
+  // PY-21175
+  public void testImplicitNegativeTypeAssertionAfterIf() {
+    doTest();
+  }
+
+  // PY-21175
+  public void testImplicitNegativeTypeAssertionAfterTwoNestedIf() {
+    doTest();
+  }
+
   private void doTestFirstStatement() {
     final String testName = getTestName(false).toLowerCase();
     configureByFile(testName + ".py");