Unary plus and minus mark operand as used

src/Psalm/Internal/Analyzer/Statements/Expression/UnaryPlusMinusAnalyzer.php

@@ -2,9 +2,13 @@
 namespace Psalm\Internal\Analyzer\Statements\Expression;
 
 use PhpParser;
+use PhpParser\Node\Expr\UnaryMinus;
+use Psalm\CodeLocation;
 use Psalm\Context;
 use Psalm\Internal\Analyzer\Statements\ExpressionAnalyzer;
 use Psalm\Internal\Analyzer\StatementsAnalyzer;
+use Psalm\Internal\Codebase\VariableUseGraph;
+use Psalm\Internal\DataFlow\DataFlowNode;
 use Psalm\Type;
 use Psalm\Type\Atomic\TFloat;
 use Psalm\Type\Atomic\TInt;
@@ -55,6 +59,39 @@ public static function analyze(
             $statements_analyzer->node_data->setType($stmt, new Type\Union($acceptable_types));
         }
 
+        self::addDataFlow(
+            $statements_analyzer,
+            $stmt,
+            $stmt->expr,
+            $stmt instanceof UnaryMinus ? 'unary-minus' : 'unary-plus'
+        );
+
         return true;
     }
+
+    private static function addDataFlow(
+        StatementsAnalyzer $statements_analyzer,
+        PhpParser\Node\Expr $stmt,
+        PhpParser\Node\Expr $value,
+        string $type
+    ): void {
+        $result_type = $statements_analyzer->node_data->getType($stmt);
+        if ($statements_analyzer->data_flow_graph instanceof VariableUseGraph && $result_type) {
+            $var_location = new CodeLocation($statements_analyzer, $stmt);
+
+            $stmt_value_type = $statements_analyzer->node_data->getType($value);
+
+            $new_parent_node = DataFlowNode::getForAssignment($type, $var_location);
+            $statements_analyzer->data_flow_graph->addNode($new_parent_node);
+            $result_type->parent_nodes = [
+                $new_parent_node->id => $new_parent_node,
+            ];
+
+            if ($stmt_value_type && $stmt_value_type->parent_nodes) {
+                foreach ($stmt_value_type->parent_nodes as $parent_node) {
+                    $statements_analyzer->data_flow_graph->addPath($parent_node, $new_parent_node, $type);
+                }
+            }
+        }
+    }
 }

tests/UnusedCodeTest.php

@@ -1029,6 +1029,26 @@ public static function foo() : Exception {
                     throw A::foo();
                 '
             ],
+            'variableUsedAsUnaryMinusOperand' => [
+                '<?php
+                    function f(): int
+                    {
+                        $a = 1;
+                        $b = -$a;
+                        return $b;
+                    }
+                ',
+            ],
+            'variableUsedAsUnaryPlusOperand' => [
+                '<?php
+                    function f(): int
+                    {
+                        $a = 1;
+                        $b = +$a;
+                        return $b;
+                    }
+                ',
+            ],
         ];
     }