Check for invalid integers in compiler's CLI (crystal-lang#13959)

src/compiler/crystal/command.cr

@@ -503,7 +503,8 @@ class Crystal::Command
           compiler.release!
         end
         opts.on("-O LEVEL", "Optimization mode: 0 (default), 1, 2, 3") do |level|
-          compiler.optimization_mode = Compiler::OptimizationMode.from_value?(level.to_i) || raise Error.new("Unknown optimization mode #{level}")
+          optimization_mode = level.to_i?.try { |v| Compiler::OptimizationMode.from_value?(v) }
+          compiler.optimization_mode = optimization_mode || raise Error.new("Invalid optimization mode: #{level}")
         end
       end
 
@@ -524,7 +525,7 @@ class Crystal::Command
           compiler.single_module = true
         end
         opts.on("--threads NUM", "Maximum number of threads to use") do |n_threads|
-          compiler.n_threads = n_threads.to_i
+          compiler.n_threads = n_threads.to_i? || raise Error.new("Invalid thread count: #{n_threads}")
         end
         unless run
           opts.on("--target TRIPLE", "Target triple") do |triple|

src/compiler/crystal/command/playground.cr

@@ -11,7 +11,9 @@ class Crystal::Command
       opts.banner = "Usage: crystal play [options] [file]\n\nOptions:"
 
       opts.on("-p PORT", "--port PORT", "Runs the playground on the specified port") do |port|
-        server.port = port.to_i
+        port = port.to_i?
+        raise Error.new("Invalid port number: #{port}") unless port && Socket::IPAddress.valid_port?(port)
+        server.port = port
       end
 
       opts.on("-b HOST", "--binding HOST", "Binds the playground to the specified IP") do |host|