PY-2783 Assignment incorrectly highlighted as unused

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

@@ -204,8 +204,9 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
       condition.accept(assertionEvaluator);
     }
     // Set the head as the last instruction of condition
-    Instruction head = getPrevInstruction(condition);
-    myBuilder.prevInstruction = head;
+    PyElement lastCondition = condition;
+    Instruction lastBranchingPoint = getPrevInstruction(condition);
+    myBuilder.prevInstruction = lastBranchingPoint;
     final PyStatementList thenStatements = ifPart.getStatementList();
     if (thenStatements != null) {
       myBuilder.startConditionalNode(thenStatements, condition, true);
@@ -224,16 +225,18 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
       myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
     }
     for (PyIfPart part : node.getElifParts()) {
-      // restore head
-      myBuilder.prevInstruction = head;
+      // Set the head as the false branch
+      myBuilder.prevInstruction = lastBranchingPoint;
+      myBuilder.startConditionalNode(part, lastCondition, false);
       condition = part.getCondition();
       if (condition != null) {
+        lastCondition = condition;
+        lastBranchingPoint = getPrevInstruction(lastCondition);
         condition.accept(this);
       }
       // Set the head as the last instruction of condition
-      head = getPrevInstruction(condition);
-      myBuilder.prevInstruction = head;
-      myBuilder.startConditionalNode(ifPart, condition, true);
+      myBuilder.prevInstruction = getPrevInstruction(lastCondition);
+      myBuilder.startConditionalNode(ifPart, lastCondition, true);
       final PyStatementList statementList = part.getStatementList();
       if (statementList != null) {
         statementList.accept(this);
@@ -250,15 +253,16 @@ public class PyControlFlowBuilder extends PyRecursiveElementVisitor {
       });
       myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
     }
-    // restore head
-    myBuilder.prevInstruction = head;
     final PyElsePart elseBranch = node.getElsePart();
     if (elseBranch != null) {
-      myBuilder.startConditionalNode(elseBranch, condition, false);
+      // Set the head as the false branch
+      myBuilder.prevInstruction = lastBranchingPoint;
+      myBuilder.startConditionalNode(elseBranch, lastCondition, false);
       elseBranch.accept(this);
       myBuilder.addPendingEdge(node, myBuilder.prevInstruction);
+    } else {
+      myBuilder.addPendingEdge(node, lastBranchingPoint);
     }
-
   }
 
   @Override

python/testData/codeInsight/controlflow/if.txt

@@ -4,12 +4,14 @@
 3(4,5) element: PyIfStatement
 4(6) element: PyStatementList. Condition: 1:true
 5(6) element: PyElsePart. Condition: 1:false
-6(7,8,9) element: PyIfStatement
-7(9) element: PyStatementList. Condition: 2:true
-8(9) element: PyIfPartIf. Condition: 3:true
-9(10,11,12) element: PyIfStatement
-10(14) element: PyStatementList. Condition: 4:true
-11(14) element: PyIfPartIf. Condition: 5:true
-12(13) element: PyElsePart. Condition: 5:false
-13(14) element: PyExpressionStatement
-14() element: null
+6(7,8) element: PyIfStatement
+7(10) element: PyStatementList. Condition: 2:true
+8(9,10) element: PyIfPartElif. Condition: 2:false
+9(10) element: PyIfPartIf. Condition: 3:true
+10(11,12) element: PyIfStatement
+11(16) element: PyStatementList. Condition: 4:true
+12(13,14) element: PyIfPartElif. Condition: 4:false
+13(16) element: PyIfPartIf. Condition: 5:true
+14(15) element: PyElsePart. Condition: 5:false
+15(16) element: PyExpressionStatement
+16() element: null

python/testData/codeInsight/controlflow/manyifs.py

@@ -0,0 +1,13 @@
+var = 1
+if a == b:
+    var = 2
+elif aa == bb:
+    bbb = same_changet_expression
+
+    if bbb:
+        var = 3 # <--- this highlight bug (unused variable)
+
+else:
+    var = 4
+
+return {'variable': var}

python/testData/codeInsight/controlflow/manyifs.txt

@@ -0,0 +1,27 @@
+0(1) element: null
+1(2) element: PyAssignmentStatement
+2(3) WRITE ACCESS: var
+3(4) element: PyIfStatement
+4(5) READ ACCESS: a
+5(6,9) READ ACCESS: b
+6(7) element: PyStatementList. Condition: a == b:true
+7(8) element: PyAssignmentStatement
+8(24) WRITE ACCESS: var
+9(10,21) element: PyIfPartElif. Condition: a == b:false
+10(11) READ ACCESS: aa
+11(12) READ ACCESS: bb
+12(13) element: PyIfPartIf. Condition: aa == bb:true
+13(14) element: PyAssignmentStatement
+14(15) READ ACCESS: same_changet_expression
+15(16) WRITE ACCESS: bbb
+16(17) element: PyIfStatement
+17(18,21) READ ACCESS: bbb
+18(19) element: PyStatementList. Condition: bbb:true
+19(20) element: PyAssignmentStatement
+20(21,24) WRITE ACCESS: var
+21(22) element: PyElsePart. Condition: aa == bb:false
+22(23) element: PyAssignmentStatement
+23(24) WRITE ACCESS: var
+24(25) element: PyReturnStatement
+25(26) READ ACCESS: var
+26() element: null

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

@@ -144,6 +144,10 @@ public class PyControlFlowBuilderTest extends LightMarkedTestCase {
     doTest();
   }
 
+  public void testManyIfs() throws Exception {
+    doTest();
+  }
+
   public void testQualifiedSelfReference() throws Exception {
     final String testName = getTestName(false).toLowerCase();
     configureByFile(testName + ".py");