Skip analysis of standard library packages using generics

The upstream analysis packages we depend on do not yet support analysis of code
using Go 1.18 type parameter features, making analysis of the Go tip standard
library choke and crash. Skip these packages for now.

PiperOrigin-RevId: 400030256

tools/nogo/nogo.go

@@ -293,6 +293,19 @@ func CheckStdlib(config *StdlibConfig, analyzers []*analysis.Analyzer) (allFindi
 		break
 	}
 
+	// Go standard library packages using Go 1.18 type parameter features.
+	//
+	// As of writing, analysis tooling is not updated to support type
+	// parameters and will choke on these packages. We skip these packages
+	// entirely for now.
+	//
+	// TODO(b/201686256): remove once tooling can handle type parameters.
+	usesTypeParams := map[string]struct{}{
+		"constraints": struct{}{}, // golang.org/issue/45458
+		"maps":        struct{}{}, // golang.org/issue/47649
+		"slices":      struct{}{}, // golang.org/issue/45955
+	}
+
 	// Aggregate all files by directory.
 	packages := make(map[string]*PackageConfig)
 	for _, file := range config.Srcs {
@@ -306,10 +319,17 @@ func CheckStdlib(config *StdlibConfig, analyzers []*analysis.Analyzer) (allFindi
 			continue // Not a file.
 		}
 		pkg := d[len(rootSrcPrefix):]
+
 		// Skip cmd packages and obvious test files: see above.
 		if strings.HasPrefix(pkg, "cmd/") || strings.HasSuffix(file, "_test.go") {
 			continue
 		}
+
+		if _, ok := usesTypeParams[pkg]; ok {
+			log.Printf("WARNING: Skipping package %q: type param analysis not yet supported", pkg)
+			continue
+		}
+
 		c, ok := packages[pkg]
 		if !ok {
 			c = &PackageConfig{