优化

src/CompilerBase.php

@@ -138,6 +138,16 @@ class CompilerBase implements PropertyAccessContext
     use LoopVarOptimizer;
     use SsaPropOptimizer;
 
+    /**
+     * Variables (and parameters) within the currently compiled function that must
+     * be emitted as a runtime variant (php::Var). A variable is recorded here when
+     * it is assigned incompatible types at different points in the body — which is
+     * perfectly legal in dynamically typed PHP but would otherwise force a strict
+     * backend to either fatal ("Cannot re-assign") or silently miscompile. The set
+     * is populated by computeVariantVars() right before the function body is parsed.
+     */
+    protected array $variantVars = [];
+
     public const string DEFAULT_PHP_VERSION = '8.5';
     protected const string NATIVE_PROPERTY_VALUE_VAR = 'var';
     protected const string NATIVE_PROPERTY_VALUE_DYNAMIC = 'dynamic';
@@ -999,6 +1009,7 @@ class CompilerBase implements PropertyAccessContext
         $this->context = new FunctionContext();
         $this->function = '';
         $this->functionDef = null;
+        $this->variantVars = [];
     }
 
     protected function resetMethod(): void
@@ -3946,6 +3957,33 @@ class CompilerBase implements PropertyAccessContext
         $this->fatalError($left, "Cannot re-assign $varName from `{$fromType}` to `{$toType}`");
     }
 
+    /**
+     * Mirror of checkVarAssignExpr()'s compatibility rules without the fatal side
+     * effect. Returns true when a variable of type $existing may legally receive a
+     * value of type $new (used by computeVariantVars() to decide whether a variable
+     * must be promoted to a runtime variant).
+     */
+    protected function areTypesAssignable(string $existing, string $new): bool
+    {
+        if ($existing === Type::VAR or $new === Type::VAR) {
+            return true;
+        }
+        if ($existing === Type::REF or $new === Type::REF) {
+            return true;
+        }
+        if ($existing === $new) {
+            return true;
+        }
+        if ($this->isNativeType($existing) and $this->isNativeType($new)) {
+            return true;
+        }
+        $bigTypes = [Type::BIGINT, Type::DECIMAL, Type::BIGFLOAT];
+        if (in_array($existing, $bigTypes, true) or in_array($new, $bigTypes, true)) {
+            return true;
+        }
+        return false;
+    }
+
     /**
      * Check a value against a composite PHP type when the value's static type
      * is precise enough to prove a mismatch. Composite declarations still use