Avoid negative indendation in formatting-preserving printer

Fixes #1015.

Author: nikic

lib/PhpParser/PrettyPrinterAbstract.php

@@ -736,7 +736,7 @@ protected function p(
                 $result .= $extraLeft;
 
                 $origIndentLevel = $this->indentLevel;
-                $this->setIndentLevel($this->origTokens->getIndentationBefore($subStartPos) + $indentAdjustment);
+                $this->setIndentLevel(max($this->origTokens->getIndentationBefore($subStartPos) + $indentAdjustment, 0));
 
                 // If it's the same node that was previously in this position, it certainly doesn't
                 // need fixup. It's important to check this here, because our fixup checks are more
@@ -839,7 +839,7 @@ protected function pArray(
                 \assert($itemStartPos >= 0 && $itemEndPos >= 0 && $itemStartPos >= $pos);
 
                 $origIndentLevel = $this->indentLevel;
-                $lastElemIndentLevel = $this->origTokens->getIndentationBefore($itemStartPos) + $indentAdjustment;
+                $lastElemIndentLevel = max($this->origTokens->getIndentationBefore($itemStartPos) + $indentAdjustment, 0);
                 $this->setIndentLevel($lastElemIndentLevel);
 
                 $comments = $arrItem->getComments();

test/code/formatPreservation/indent.test

@@ -35,3 +35,36 @@ if ($a) {
 @@{"\t"}@@$x;
 @@{"\t"}@@$y;
 }
+-----
+<?php
+array_merge(
+    [
+$x,
+        $y,
+    ]
+);
+-----
+$call = $stmts[0]->expr;
+$stmts[0]->expr = new Expr\StaticCall(new Node\Name\FullyQualified('Compat'), $call->name, $call->args);
+-----
+<?php
+\Compat::array_merge([
+$x,
+    $y,
+]);
+-----
+<?php
+if ($a) {
+        if (
+$b
+        ) {}
+}
+-----
+$stmts[0] = new Stmt\While_($stmts[0]->cond, $stmts[0]->stmts);
+-----
+<?php
+while ($a) {
+    if (
+$b
+    ) {}
+}