compiler: add support for type parameters (aka generics)

...that was surprisingly easy.

loader/loader_go118.go

@@ -0,0 +1,18 @@
+//go:build go1.18
+// +build go1.18
+
+package loader
+
+// Workaround for Go 1.17 support. Should be removed once we drop Go 1.17
+// support.
+
+import (
+	"go/ast"
+	"go/types"
+)
+
+func init() {
+	addInstances = func(info *types.Info) {
+		info.Instances = make(map[*ast.Ident]types.Instance)
+	}
+}