Added implied mixed return type to ResolverInterface::retrieveValue

src/SDK/Common/Configuration/Resolver/EnvironmentResolver.php

@@ -24,11 +24,7 @@ class EnvironmentResolver implements ResolverInterface
         return !Configuration::isEmpty($env);
     }
 
-    /**
-     * @psalm-suppress InvalidReturnStatement
-     * @psalm-suppress InvalidReturnType
-     */
-    public function retrieveValue(string $variableName)
+    public function retrieveValue(string $variableName): mixed
     {
         $value = getenv($variableName);
         if ($value === false) {

src/SDK/Common/Configuration/Resolver/PhpIniResolver.php

@@ -16,7 +16,7 @@ class PhpIniResolver implements ResolverInterface
     {
     }
 
-    public function retrieveValue(string $variableName)
+    public function retrieveValue(string $variableName): mixed
     {
         $value = $this->accessor->get($variableName) ?: '';
         if (is_array($value)) {

src/SDK/Common/Configuration/Resolver/ResolverInterface.php

@@ -6,10 +6,7 @@ namespace OpenTelemetry\SDK\Common\Configuration\Resolver;
 
 interface ResolverInterface
 {
-    /**
-     * @return mixed
-     */
-    public function retrieveValue(string $variableName);
+    public function retrieveValue(string $variableName): mixed;
 
     public function hasVariable(string $variableName): bool;
 }

src/SDK/Common/Configuration/Resolver/SdkConfigurationResolver.php

@@ -36,7 +36,7 @@ class SdkConfigurationResolver implements ResolverInterface
         $this->reader = new EnvSourceReader($envSources);
     }
 
-    public function retrieveValue(string $variableName)
+    public function retrieveValue(string $variableName): mixed
     {
         return $this->reader->read($variableName);
     }