Add NullOperand issue for easy ignoring

psalm.xml

@@ -12,6 +12,8 @@
     </inspectFiles>
 
     <issueHandler>
+        <NullOperand errorLevel="suppress" />
+
         <MissingReturnType>
             <excludeFiles>
                 <directory name="tests" />

src/Psalm/Checker/ClassLikeChecker.php

@@ -565,7 +565,7 @@ abstract class ClassLikeChecker extends SourceChecker implements StatementsSourc
             $method_checker = self::$method_checkers[$method_id];
         }
 
-        if (!$stmt->isAbstract()) {
+        if (!$stmt->isAbstract() && $class_context->self) {
             MethodChecker::setDeclaringMethodId(
                 $class_context->self . '::' . $this->getMappedMethodName(strtolower($stmt->name)),
                 $method_id

src/Psalm/Checker/Statements/Block/ForeachChecker.php

@@ -169,7 +169,7 @@ class ForeachChecker
             }
         }
 
-        if ($stmt->keyVar && $stmt->keyVar instanceof PhpParser\Node\Expr\Variable) {
+        if ($stmt->keyVar && $stmt->keyVar instanceof PhpParser\Node\Expr\Variable && is_string($stmt->keyVar->name)) {
             $foreach_context->vars_in_scope['$' . $stmt->keyVar->name] = $key_type ?: Type::getMixed();
             $foreach_context->vars_possibly_in_scope['$' . $stmt->keyVar->name] = true;
             $statements_checker->registerVariable('$' . $stmt->keyVar->name, $stmt->getLine());

src/Psalm/Checker/Statements/Expression/AssignmentChecker.php

@@ -525,7 +525,7 @@ class AssignmentChecker
                 if ($class_property_type === false) {
                     if (IssueBuffer::accepts(
                         new MissingPropertyType(
-                            'Property ' . $lhs_type_part->value . '::$' . $stmt->name . ' does not have a declared ' .
+                            'Property ' . $lhs_type_part->value . '::$' . $prop_name . ' does not have a declared ' .
                                 'type',
                             new CodeLocation($statements_checker->getSource(), $stmt)
                         ),
@@ -650,6 +650,10 @@ class AssignmentChecker
 
         $prop_name = $stmt->name;
 
+        if (!is_string($prop_name)) {
+            return;
+        }
+
         if (!isset($class_properties[$prop_name])) {
             $all_class_properties = null;
 

src/Psalm/Checker/Statements/ExpressionChecker.php

@@ -21,6 +21,7 @@ use Psalm\Issue\InvalidOperand;
 use Psalm\Issue\InvalidScope;
 use Psalm\Issue\InvalidStaticVariable;
 use Psalm\Issue\MixedOperand;
+use Psalm\Issue\NullOperand;
 use Psalm\Issue\PossiblyUndefinedVariable;
 use Psalm\Issue\UndefinedVariable;
 use Psalm\Issue\UnrecognizedExpression;
@@ -1071,28 +1072,48 @@ class ExpressionChecker
                 return;
             }
 
+            if ($left_type->isNullable()) {
+                if (IssueBuffer::accepts(
+                    new NullOperand(
+                        'Cannot concatenate with a ' . $left_type,
+                        new CodeLocation($statements_checker->getSource(), $left)
+                    ),
+                    $statements_checker->getSuppressedIssues()
+                )) {
+                    // fall through
+                }
+            }
+
+            if ($right_type->isNullable()) {
+                if (IssueBuffer::accepts(
+                    new NullOperand(
+                        'Cannot concatenate with a ' . $right_type,
+                        new CodeLocation($statements_checker->getSource(), $right)
+                    ),
+                    $statements_checker->getSuppressedIssues()
+                )) {
+                    // fall through
+                }
+            }
+
             $left_type_match = TypeChecker::isContainedBy(
                 $left_type,
                 Type::getString(),
-                false,
-                $left_has_scalar_match,
-                $left_type_coerced,
-                $left_to_string_cast
+                true,
+                $left_has_scalar_match
             );
 
             $right_type_match = TypeChecker::isContainedBy(
                 $right_type,
                 Type::getString(),
-                false,
-                $right_has_scalar_match,
-                $right_type_coerced,
-                $right_to_string_cast
+                true,
+                $right_has_scalar_match
             );
 
             if (!$left_type_match && (!$left_has_scalar_match || $config->strict_binary_operands)) {
                 if (IssueBuffer::accepts(
                     new InvalidOperand(
-                        'Cannot concatenate a string and a ' . $left_type,
+                        'Cannot concatenate with a ' . $left_type,
                         new CodeLocation($statements_checker->getSource(), $left)
                     ),
                     $statements_checker->getSuppressedIssues()
@@ -1104,7 +1125,7 @@ class ExpressionChecker
             if (!$right_type_match && (!$right_has_scalar_match || $config->strict_binary_operands)) {
                 if (IssueBuffer::accepts(
                     new InvalidOperand(
-                        'Cannot concatenate a string and a ' . $right_type,
+                        'Cannot concatenate with a ' . $right_type,
                         new CodeLocation($statements_checker->getSource(), $right)
                     ),
                     $statements_checker->getSuppressedIssues()

src/Psalm/Checker/TypeChecker.php

@@ -288,6 +288,7 @@ class TypeChecker
      */
     public static function getTruthsFromFormula(array $clauses)
     {
+        /** @var array<string, string> */
         $truths = [];
 
         if (empty($clauses)) {

src/Psalm/Issue/NullOperand.php

@@ -0,0 +1,6 @@
+<?php
+namespace Psalm\Issue;
+
+class NullOperand extends CodeError
+{
+}