fix: resolve regexp package identity via type checker in regexpcompileinfunction linter

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Author: Copilot

pkg/linters/regexpcompileinfunction/regexpcompileinfunction.go

@@ -34,7 +34,7 @@ func run(pass *analysis.Pass) (any, error) {
 
 	for cur := range insp.Root().Preorder((*ast.CallExpr)(nil)) {
 		call, ok := cur.Node().(*ast.CallExpr)
-		if !ok || !isRegexpCompileCall(call) {
+		if !ok || !isRegexpCompileCall(pass, call) {
 			continue
 		}
 		if !hasConstantStringPattern(pass, call) {
@@ -68,17 +68,27 @@ func run(pass *analysis.Pass) (any, error) {
 	return nil, nil
 }
 
-// isRegexpCompileCall checks if the call is to regexp.MustCompile or regexp.Compile.
-func isRegexpCompileCall(call *ast.CallExpr) bool {
+// isRegexpCompileCall checks if the call is to regexp.MustCompile or regexp.Compile,
+// resolving the package identity via the type checker to handle aliased imports
+// and avoid false positives from local identifiers named "regexp".
+func isRegexpCompileCall(pass *analysis.Pass, call *ast.CallExpr) bool {
 	sel, ok := call.Fun.(*ast.SelectorExpr)
 	if !ok {
 		return false
 	}
+	if sel.Sel.Name != "MustCompile" && sel.Sel.Name != "Compile" {
+		return false
+	}
 	ident, ok := sel.X.(*ast.Ident)
-	if !ok {
+	if !ok || pass.TypesInfo == nil {
+		return false
+	}
+	obj := pass.TypesInfo.ObjectOf(ident)
+	if obj == nil {
 		return false
 	}
-	return ident.Name == "regexp" && (sel.Sel.Name == "MustCompile" || sel.Sel.Name == "Compile")
+	pkgName, ok := obj.(*types.PkgName)
+	return ok && pkgName.Imported().Path() == "regexp"
 }
 
 // hasConstantStringPattern checks whether the regexp pattern is a compile-time constant string,

pkg/linters/regexpcompileinfunction/testdata/src/regexpcompileinfunction/alias_import.go

@@ -0,0 +1,20 @@
+package regexpcompileinfunction
+
+import re "regexp"
+
+// flagged: aliased import of regexp — alias must not cause a false negative.
+func ProcessWithAlias(s string) bool {
+	r := re.MustCompile(`^[a-z]+$`) // want `regexp compilation inside function should be moved to package-level variable`
+	return r.MatchString(s)
+}
+
+func ValidateWithAlias(input string) (bool, error) {
+	r, err := re.Compile(`\d+`) // want `regexp compilation inside function should be moved to package-level variable`
+	if err != nil {
+		return false, err
+	}
+	return r.MatchString(input), nil
+}
+
+// not flagged: aliased import at package level is fine.
+var packageLevelAliasRegexp = re.MustCompile(`^[a-z]+$`)

pkg/linters/regexpcompileinfunction/testdata/src/regexpcompileinfunction/shadowed_identifier.go

@@ -0,0 +1,14 @@
+package regexpcompileinfunction
+
+// customRegexp is an unrelated type that happens to have Compile/MustCompile methods.
+type customRegexp struct{}
+
+func (customRegexp) Compile(_ string) (*customRegexp, error) { return &customRegexp{}, nil }
+func (customRegexp) MustCompile(_ string) *customRegexp      { return &customRegexp{} }
+
+// not flagged: local variable named "regexp" is not the stdlib regexp package.
+func GoodShadowedRegexpIdentifier(s string) bool {
+	regexp := customRegexp{}
+	_ = regexp.MustCompile(s)
+	return true
+}