Resolve types of arrow function parameters used as arguments

go.mod

@@ -2,4 +2,4 @@ module github.com/rectorphp/argtyper
 
 go 1.26
 
-require github.com/rectorphp/php-parser-in-go v0.1.1
+require github.com/rectorphp/php-parser-in-go v0.1.2-0.20260914171035-ef8c7cbb139d

go.sum

@@ -2,7 +2,7 @@ github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/rectorphp/php-parser-in-go v0.1.1 h1:9jMbxAtDBjubUlPFKB5lbbvpXn8Otxq9eG77Q7moqwk=
-github.com/rectorphp/php-parser-in-go v0.1.1/go.mod h1:6p9QnZnLGc9uruvKuSXlVt4uSIY5Rqe6h2aj9+hEBG8=
+github.com/rectorphp/php-parser-in-go v0.1.2-0.20260914171035-ef8c7cbb139d h1:T26rEJvnupxPmDhRGulHue2rj83Ncl6DtjCLbbMFjT4=
+github.com/rectorphp/php-parser-in-go v0.1.2-0.20260914171035-ef8c7cbb139d/go.mod h1:6p9QnZnLGc9uruvKuSXlVt4uSIY5Rqe6h2aj9+hEBG8=
 gotest.tools v2.2.0+incompatible h1:VsBPFP1AI068pPrMxtb/S8Zkgf9xEmTLJjfM+P5UIEo=
 gotest.tools v2.2.0+incompatible/go.mod h1:DsYFclhRJ6vuDpmuTbkuFWG+y2sxOXAzmJt81HFBacw=

internal/apply/apply_test.go

@@ -200,6 +200,11 @@ func TestApply(t *testing.T) {
 			},
 			want: "<?php\nnamespace App;\n\nfunction handle(\\App\\Entity\\Lead $item) {}",
 		},
+		{
+			name:   "qualifies arrow function typed parameter argument from use import",
+			target: "<?php\nnamespace App;\n\nuse App\\Entity\\Lead;\n\nfinal class Repo {\n    public function save($entity) {}\n    public function go() { $run = fn (Lead $lead) => $this->save($lead); }\n}",
+			want:   "<?php\nnamespace App;\n\nuse App\\Entity\\Lead;\n\nfinal class Repo {\n    public function save(\\App\\Entity\\Lead $entity) {}\n    public function go() { $run = fn (Lead $lead) => $this->save($lead); }\n}",
+		},
 		{
 			name:   "qualifies typed parameter argument from use import",
 			target: "<?php\nnamespace App;\n\nuse App\\Entity\\Lead;\n\nfinal class Repo {\n    public function save($entity) {}\n    public function go(Lead $lead) { $this->save($lead); }\n}",

internal/collect/collect.go

@@ -75,6 +75,10 @@ func (c *collector) walk(node ast.Vertex, sc scope) {
 	case *ast.ExprClosure:
 		sc.params = c.paramClasses(typed.Params, sc.classFQCN)
 		sc.locals = c.localClasses(typed.Stmts)
+	case *ast.ExprArrowFunction:
+		// arrow functions capture outer variables, so keep the inherited params
+		// and locals and overlay the arrow's own typed parameters.
+		sc.params = merge(sc.params, c.paramClasses(typed.Params, sc.classFQCN))
 	}
 
 	c.visit(node, sc)
@@ -291,6 +295,21 @@ func (c *collector) classFromType(typeNode ast.Vertex, enclosing string) string
 	return name
 }
 
+// merge overlays the over map onto a copy of base, with over winning on clashes.
+func merge(base, over map[string]string) map[string]string {
+	if len(over) == 0 {
+		return base
+	}
+	merged := make(map[string]string, len(base)+len(over))
+	for name, class := range base {
+		merged[name] = class
+	}
+	for name, class := range over {
+		merged[name] = class
+	}
+	return merged
+}
+
 // shortName returns the last segment of a fully qualified name, the form used
 // as a method lookup key.
 func shortName(fqcn string) string {