refactor: extract foreign-region helpers to satisfy funlen

Fold the config validation calls into validateConfigSemantics and the
runner's foreign-region check into checkWithForeignRegions so
loadFromBytes and lintFile stay under the funlen budget.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EwKxDxhjkTQPPkBrNhsrNG

Author: claude

internal/config/foreignregion.go

@@ -28,6 +28,17 @@ func EffectiveForeignRegions(cfg *Config, filePath string) []ForeignRegion {
 	return out
 }
 
+// validateConfigSemantics runs the post-parse structural checks that
+// depend on the fully-decoded config: kind graph validity and
+// foreign-region marker-pair well-formedness. Kept together so
+// loadFromBytes carries one call site rather than one per check.
+func validateConfigSemantics(cfg *Config) error {
+	if err := ValidateKinds(cfg); err != nil {
+		return err
+	}
+	return validateForeignRegions(cfg)
+}
+
 // validateForeignRegions rejects malformed marker-pair declarations:
 // a blank start or end marker, or a pair whose start equals its end
 // (the scanner could never tell which line opens and which closes a

internal/config/load.go

@@ -101,11 +101,7 @@ func loadFromBytes(data []byte, sourcePath string, mergeKinds bool) (*Config, er
 		return nil, err
 	}
 
-	if err := ValidateKinds(&cfg); err != nil {
-		return nil, fmt.Errorf("validating config: %w", err)
-	}
-
-	if err := validateForeignRegions(&cfg); err != nil {
+	if err := validateConfigSemantics(&cfg); err != nil {
 		return nil, fmt.Errorf("validating config: %w", err)
 	}
 

internal/engine/runner.go

@@ -486,18 +486,11 @@ func (r *Runner) lintFile(path string, intraFileCap int, cache *lint.RunCache, r
 	// directives, so it has no generated sections — leave the ranges nil.
 	populateGeneratedRanges(f)
 
-	// Foreign-region ranges extend the same exclusion set from a plain
-	// line scan (no AST needed), so style rules skip diagnostics inside a
-	// marker pair another generator owns. Malformed pairs surface as
-	// MDS073 diagnostics appended after the rule check.
-	foreignDiags := foreignregion.Apply(f, r.Config, path)
-
 	// Configure the enabled rules once per config signature (cached on the
 	// worker's confCache) and reuse the result across every file that shares
 	// that config, instead of re-cloning every Configurable rule per file.
 	configured, cfgErrs := rr.configured(sigKey, effective)
-	diags := checker.CheckConfiguredRules(f, configured, r.SkipSourceContext, intraFileCap)
-	diags = append(diags, foreignDiags...)
+	diags := r.checkWithForeignRegions(f, configured, path, intraFileCap)
 	if r.Explain {
 		explain.Attach(diags, r.Config, path, fmKinds, fmFields)
 	}
@@ -508,6 +501,19 @@ func (r *Runner) lintFile(path string, intraFileCap int, cache *lint.RunCache, r
 	return fileOutcome{diags: diags, errs: cfgErrs}
 }
 
+// checkWithForeignRegions extends f.GeneratedRanges with the foreign-
+// region spans that apply to path (a plain line scan, no AST needed) so
+// style rules skip diagnostics inside a marker pair another generator
+// owns, runs the configured rules, and appends the malformed-region
+// (MDS073) diagnostics for any unmatched or duplicated marker.
+func (r *Runner) checkWithForeignRegions(
+	f *lint.File, configured []rule.Rule, path string, intraFileCap int,
+) []lint.Diagnostic {
+	foreignDiags := foreignregion.Apply(f, r.Config, path)
+	diags := checker.CheckConfiguredRules(f, configured, r.SkipSourceContext, intraFileCap)
+	return append(diags, foreignDiags...)
+}
+
 // populateGeneratedRanges fills f.GeneratedRanges from the include/catalog
 // markers in its AST. The flat Layer-0 and Layer 0 parse-skip paths leave
 // f.AST nil (and only take that path for files with no such directive, so