Add support for infinite loops

Fixes #381

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

@@ -2,6 +2,7 @@
 namespace Psalm\Checker\Statements\Block;
 
 use PhpParser;
+use Psalm\Checker\ScopeChecker;
 use Psalm\Checker\Statements\ExpressionChecker;
 use Psalm\Checker\StatementsChecker;
 use Psalm\Context;
@@ -27,21 +28,50 @@ class ForChecker
             }
         }
 
+        $while_true = !$stmt->cond && !$stmt->init && !$stmt->loop;
+
+        $pre_context = $while_true ? clone $context : null;
+
         $for_context = clone $context;
         $for_context->inside_loop = true;
 
+        $loop_scope = new LoopScope($for_context, $context);
+
         LoopChecker::analyze(
             $statements_checker,
             $stmt->stmts,
             $stmt->cond,
             $stmt->loop,
-            new LoopScope($for_context, $context)
+            $loop_scope,
+            $inner_loop_context
         );
 
+        if ($inner_loop_context && $while_true) {
+            // if we actually leave the loop
+            if (in_array(ScopeChecker::ACTION_BREAK, $loop_scope->final_actions, true)
+                || in_array(ScopeChecker::ACTION_END, $loop_scope->final_actions, true)
+            ) {
+                foreach ($inner_loop_context->vars_in_scope as $var_id => $type) {
+                    if (!isset($context->vars_in_scope[$var_id])) {
+                        $context->vars_in_scope[$var_id] = $type;
+                    }
+                }
+            }
+        }
+
+        if (!$while_true
+            || in_array(ScopeChecker::ACTION_BREAK, $loop_scope->final_actions, true)
+            || in_array(ScopeChecker::ACTION_END, $loop_scope->final_actions, true)
+            || !$pre_context
+        ) {
             $context->vars_possibly_in_scope = array_merge(
-            $for_context->vars_possibly_in_scope,
+                $context->vars_possibly_in_scope,
-            $context->vars_possibly_in_scope
+                $for_context->vars_possibly_in_scope
             );
+        } else {
+            $context->vars_in_scope = $pre_context->vars_in_scope;
+            $context->vars_possibly_in_scope = $pre_context->vars_possibly_in_scope;
+        }
 
         $context->referenced_var_ids = array_merge(
             $for_context->referenced_var_ids,

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

@@ -2,6 +2,7 @@
 namespace Psalm\Checker\Statements\Block;
 
 use PhpParser;
+use Psalm\Checker\ScopeChecker;
 use Psalm\Checker\StatementsChecker;
 use Psalm\Context;
 use Psalm\Scope\LoopScope;
@@ -20,20 +21,55 @@ class WhileChecker
         PhpParser\Node\Stmt\While_ $stmt,
         Context $context
     ) {
+        $while_true = $stmt->cond
+            && ($stmt->cond instanceof PhpParser\Node\Expr\ConstFetch && $stmt->cond->name->parts === ['true'])
+                || ($stmt->cond instanceof PhpParser\Node\Scalar\LNumber && $stmt->cond->value > 0);
+
+        $pre_context = null;
+
+        if ($while_true) {
+            $pre_context = clone $context;
+        }
+
         $while_context = clone $context;
 
+        $loop_scope = new LoopScope($while_context, $context);
+
         LoopChecker::analyze(
             $statements_checker,
             $stmt->stmts,
             $stmt->cond ? [$stmt->cond] : [],
             [],
-            new LoopScope($while_context, $context)
+            $loop_scope,
+            $inner_loop_context
         );
 
+        if ($inner_loop_context && $while_true) {
+            // if we actually leave the loop
+            if (in_array(ScopeChecker::ACTION_BREAK, $loop_scope->final_actions, true)
+                || in_array(ScopeChecker::ACTION_END, $loop_scope->final_actions, true)
+            ) {
+                foreach ($inner_loop_context->vars_in_scope as $var_id => $type) {
+                    if (!isset($context->vars_in_scope[$var_id])) {
+                        $context->vars_in_scope[$var_id] = $type;
+                    }
+                }
+            }
+        }
+
+        if (!$while_true
+            || in_array(ScopeChecker::ACTION_BREAK, $loop_scope->final_actions, true)
+            || in_array(ScopeChecker::ACTION_END, $loop_scope->final_actions, true)
+            || !$pre_context
+        ) {
             $context->vars_possibly_in_scope = array_merge(
                 $context->vars_possibly_in_scope,
                 $while_context->vars_possibly_in_scope
             );
+        } else {
+            $context->vars_in_scope = $pre_context->vars_in_scope;
+            $context->vars_possibly_in_scope = $pre_context->vars_possibly_in_scope;
+        }
 
         $context->referenced_var_ids = array_merge(
             $context->referenced_var_ids,

tests/LoopScopeTest.php

@@ -764,6 +764,26 @@ class LoopScopeTest extends TestCase
                     'MixedAssignment', 'MixedArrayAccess',
                 ],
             ],
+            'whileTrue' => [
+                '<?php
+                    while (true) {
+                        $a = "hello";
+                        break;
+                    }
+                    while (1) {
+                        $b = 5;
+                        break;
+                    }
+                    for(;;) {
+                        $c = true;
+                        break;
+                    }',
+                'assignments' => [
+                    '$a' => 'string',
+                    '$b' => 'int',
+                    '$c' => 'bool',
+                ],
+            ],
         ];
     }
 
@@ -898,6 +918,24 @@ class LoopScopeTest extends TestCase
                     }',
                 'error_message' => 'RedundantCondition',
             ],
+            'whileTrueNoBreak' => [
+                '<?php
+                    while (true) {
+                        $a = "hello";
+                    }
+
+                    echo $a;',
+                'error_message' => 'UndefinedGlobalVariable',
+            ],
+            'forInfiniteNoBreak' => [
+                '<?php
+                    for (;;) {
+                        $a = "hello";
+                    }
+
+                    echo $a;',
+                'error_message' => 'UndefinedGlobalVariable',
+            ],
         ];
     }
 }