Static Type Checking & @CompileStatic

import groovy.transform.TypeChecked

@TypeChecked
void flow(Object o) {
    if (o instanceof String) {
        println o.toUpperCase()      // o is a String in this branch
    } else if (o instanceof Integer) {
        println o + 1                // o is an Integer in this branch
    }
    def x = 'text'
    println x.length()               // x holds a String
    x = 42
    println x.intValue()             // x now holds an Integer
    x = 'again'
    println x.toUpperCase()          // and a String again
}
flow('abc')
flow(4)

ABC
4
42
AGAIN
5
4
42
AGAIN

import groovy.transform.TypeChecked

@TypeChecked
void bad(Object o) {
    def x = 'text'
    x = 42
    println x.length()
}

f2.groovy: 7: [Static type checking] - Cannot find matching method java.lang.Integer#length(). Please check if the declared type is correct and if the method exists.
 @ line 7, column 13.
       println x.length()
               ^

import groovy.transform.TypeChecked

@TypeChecked
void lub(boolean flag) {
    def v = flag ? 1 : 2.5d                        // Integer and Double: both are Number
    println v.intValue()
    def w = flag ? 'a' : new StringBuilder('b')    // String and StringBuilder: both are CharSequence
    println w.length()
    def l = [1, 2.5, 3L]                           // a List of Number
    println l.first().intValue()
}
lub(true)

1
1
1

import groovy.transform.TypeChecked

@TypeChecked
void lub2(boolean flag) {
    def v = flag ? 1 : 'one'
    println v.toUpperCase()
}

f4.groovy: 6: [Static type checking] - Cannot find matching method (java.io.Serializable & java.lang.Comparable & java.lang.constant.Constable & java.lang.constant.ConstantDesc)#toUpperCase(). Please check if the declared type is correct and if the method exists.
 @ line 6, column 13.
       println v.toUpperCase()
               ^

import groovy.transform.TypeChecked

@TypeChecked
void shared() {
    def x = 1
    def c = { x = 'text' }     // x is assigned a String inside the closure
    c()
    println x.intValue()
}

l1.groovy: 8: [Static type checking] - Cannot find matching method (java.io.Serializable & java.lang.Comparable & java.lang.constant.Constable & java.lang.constant.ConstantDesc)#intValue(). Please check if the declared type is correct and if the method exists.
 @ line 8, column 13.
       println x.intValue()
               ^

import groovy.transform.TypeChecked

@TypeChecked
void closures() {
    def names = ['basil', 'mint']
    println names.collect { it.toUpperCase() }
    println names.inject(0) { acc, s -> acc + s.length() }
    def m = [a: 1, b: 2]
    m.each { k, v -> println k.toUpperCase() + (v + 1) }
}
closures()

[BASIL, MINT]
9
A2
B3

f6.groovy: 6: [Static type checking] - Cannot find matching method java.lang.String#toUpperCasee(). Please check if the declared type is correct and if the method exists.
 @ line 6, column 29.
       println names.collect { it.toUpperCasee() }
                               ^

import groovy.transform.CompileStatic
import groovy.transform.TypeChecked

String pick(Object o) { 'object' }
String pick(String s) { 'string' }

String dynamicPick(Object o) { pick(o) }

@TypeChecked
String checkedPick(Object o) { pick(o) }

@CompileStatic
String staticPick(Object o) { pick(o) }

Object value = 'x'
println dynamicPick(value)
println checkedPick(value)
println staticPick(value)

string
string
object

import groovy.transform.CompileStatic

class Bench {
    static long dynamicSum(n) {
        def total = 0L
        for (i in 0..<n) { total += i % 7 }
        total
    }
    @CompileStatic
    static long staticSum(int n) {
        long total = 0L
        for (int i = 0; i < n; i++) { total += i % 7 }
        total
    }
}

def time = { String label, Closure body ->
    body()                                  // warm up
    long t0 = System.nanoTime()
    def r = body()
    long ms = (System.nanoTime() - t0).intdiv(1_000_000)
    println "${label}: result=${r}"
    ms
}
int n = 50_000_000
long d = time('dynamic') { Bench.dynamicSum(n) }
long s = time('static ') { Bench.staticSum(n) }
println "static is faster: ${s < d}"
println "dynamic ${d} ms, static ${s} ms"

dynamic: result=149999997
static : result=149999997
static is faster: true
dynamic 170 ms, static 29 ms

import groovy.transform.CompileStatic

@CompileStatic
class Outer {
    List<String> upper(List<String> xs) { xs.collect { it.toUpperCase() } }
    static class Inner { int twice(int n) { n * 2 } }
}
println new Outer().upper(['a', 'b'])
println new Outer.Inner().twice(4)
println Outer.Inner.getDeclaredMethods().find { it.name == 'twice' }

[A, B]
8
public int Outer$Inner.twice(int)

import groovy.transform.CompileStatic

class Greeter {
    def methodMissing(String name, args) { "dynamic ${name}" }
}

def dyn() { new Greeter().hello() }
println dyn()

@CompileStatic
class Strict { String callIt() { new Greeter().hello() } }

h1.groovy: 11: [Static type checking] - Cannot find matching method Greeter#hello(). Please check if the declared type is correct and if the method exists.
 @ line 11, column 34.
   class Strict { String callIt() { new Greeter().hello() } }
                                    ^

import groovy.transform.CompileStatic

String.metaClass.shout = { -> delegate.toUpperCase() + '!' }

def dynamicShout() { 'hi'.shout() }
println dynamicShout()

@CompileStatic
String staticShout() { 'hi'.shout() }

h3.groovy: 9: [Static type checking] - Cannot find matching method java.lang.String#shout(). Please check if the declared type is correct and if the method exists.
 @ line 9, column 24.
   String staticShout() { 'hi'.shout() }
                          ^

import groovy.transform.CompileStatic

class Config { Map<String, Object> values = [:] }

@CompileStatic
class Svc {
    int total(Config c) {
        int sum = 0
        c.values.each { k, v -> sum += (v as int) }   // as-coercions still work
        sum
    }
    def broken(Config c) { c.size }                   // Config has no size property
}

h5.groovy: 13: [Static type checking] - No such property: size for class: Config
 @ line 13, column 28.
       def broken(Config c) { c.size }
                              ^