Fix #2139 - allow comprehension of constant ternaries

src/Psalm/Internal/Codebase/ClassLikes.php

@@ -38,6 +38,7 @@ use function strlen;
 use function strrpos;
 use function strtolower;
 use function substr;
+use Psalm\Internal\Scanner\UnresolvedConstantComponent;
 
 /**
  * @internal
@@ -1557,6 +1558,25 @@ class ClassLikes
             return new Type\Atomic\TMixed;
         }
 
+        if ($c instanceof UnresolvedConstant\UnresolvedTernary) {
+            $cond = $this->resolveConstantType($c->cond, $statements_analyzer);
+            $if = $c->if ? $this->resolveConstantType($c->if, $statements_analyzer) : null;
+            $else = $this->resolveConstantType($c->else, $statements_analyzer);
+
+            if ($cond instanceof Type\Atomic\TLiteralFloat
+                || $cond instanceof Type\Atomic\TLiteralInt
+                || $cond instanceof Type\Atomic\TLiteralString
+            ) {
+                if ($cond->value) {
+                    return $if ? $if : $cond;
+                }
+            } elseif ($cond instanceof Type\Atomic\TFalse || $cond instanceof Type\Atomic\TNull) {
+                return $else;
+            } elseif ($cond instanceof Type\Atomic\TTrue) {
+                return $if ? $if : $cond;
+            }
+        }
+
         if ($c instanceof UnresolvedConstant\ArrayValue) {
             $properties = [];
 

src/Psalm/Internal/Scanner/UnresolvedConstant/UnresolvedTernary.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Psalm\Internal\Scanner\UnresolvedConstant;
+
+use Psalm\Internal\Scanner\UnresolvedConstantComponent;
+
+class UnresolvedTernary extends UnresolvedConstantComponent
+{
+    public $cond;
+    public $if;
+    public $else;
+
+    public function __construct(
+        UnresolvedConstantComponent $cond,
+        ?UnresolvedConstantComponent $if,
+        UnresolvedConstantComponent $else
+    ) {
+        $this->cond = $cond;
+        $this->if = $if;
+        $this->else = $else;
+    }
+}

src/Psalm/Internal/Visitor/ReflectorVisitor.php

@@ -3283,6 +3283,38 @@ class ReflectorVisitor extends PhpParser\NodeVisitorAbstract implements PhpParse
             }
         }
 
+        if ($stmt instanceof PhpParser\Node\Expr\Ternary) {
+            $cond = self::getUnresolvedClassConstExpr(
+                $stmt->cond,
+                $aliases,
+                $fq_classlike_name
+            );
+
+            $if = null;
+
+            if ($stmt->if) {
+                $if = self::getUnresolvedClassConstExpr(
+                    $stmt->if,
+                    $aliases,
+                    $fq_classlike_name
+                );
+
+                if ($if === null) {
+                    $if = false;
+                }
+            }
+
+            $else = self::getUnresolvedClassConstExpr(
+                $stmt->else,
+                $aliases,
+                $fq_classlike_name
+            );
+
+            if ($cond && $else && $if !== false) {
+                return new UnresolvedConstant\UnresolvedTernary($cond, $if, $else);
+            }
+        }
+
         if ($stmt instanceof PhpParser\Node\Expr\ConstFetch) {
             if (strtolower($stmt->name->parts[0]) === 'false') {
                 return new UnresolvedConstant\ScalarValue(false);

tests/ConstantTest.php

@@ -429,6 +429,16 @@ class ConstantTest extends TestCase
                         const Z = self::X;
                     }'
             ],
+            'supportTernaries' => [
+                '<?php
+                    const cons1 = true;
+
+                    class Clazz {
+                        const cons2 = (cons1) ? 1 : 0;
+                    }
+
+                    echo Clazz::cons2;',
+            ]
         ];
     }