Smart casts for local variables not captured in a closure and not changed in a loop, see #KT-3175.

isLocalVariable added. Assignment / initialization analysis.
Control whether a variable is changed in a loop at the beginning and at the end of the loop.
Control whether a variable is captured in a closure. #KT-3175  Fixed. #KT-2266  Fixed.
Tests for variable null safety and for variables is/as operations.
Loop / closure / variable property tests are included.
Old tests changed in accordance with KT-3175. In particular, all three of testSmartcastImpossible were fixed.

idea/testData/checker/BinaryCallsOnNullableValues.kt

@@ -5,10 +5,10 @@ class A() {
 fun f(): Unit {
   var x: Int? = <warning>1</warning>
   x = 1
-  x <error>+</error> 1
-  x <error>plus</error> 1
-  x <error><</error> 1
-  x <error>+=</error> 1
+  x + 1
+  x plus 1
+  x < 1
+  x += 1
 
   x == 1
   x != 1
@@ -21,8 +21,8 @@ fun f(): Unit {
   x === 1
   x !== 1
 
-  x<error>..</error>2
-  <error>x</error> in 1..2
+  x..2
+  x in 1..2
 
   val y : Boolean? = true
   <warning>false || <error>y</error></warning>

idea/testData/checker/infos/SmartCasts.kt

@@ -198,8 +198,8 @@ fun mergeSmartCasts(a: Any?) {
 fun f(): String {
     var <info>a</info>: Any = 11
     if (<info>a</info> is String) {
-        val <warning>i</warning>: String = <error descr="[SMARTCAST_IMPOSSIBLE] Smart cast to 'kotlin.String' is impossible, because 'a' could have changed since the is-check">a</error>
-        <error descr="[SMARTCAST_IMPOSSIBLE] Smart cast to 'kotlin.String' is impossible, because 'a' could have changed since the is-check">a</error>.compareTo("f")
+        val <warning>i</warning>: String = <info descr="Smart cast to kotlin.String"><info descr="Wrapped into a reference object to be modified when captured in a closure">a</info></info>
+        <info descr="Smart cast to kotlin.String"><info descr="Wrapped into a reference object to be modified when captured in a closure">a</info></info>.compareTo("f")
         val <warning>f</warning>: Function0<String> = { <error descr="[SMARTCAST_IMPOSSIBLE] Smart cast to 'kotlin.String' is impossible, because 'a' could have changed since the is-check">a</error> }
         return <error descr="[SMARTCAST_IMPOSSIBLE] Smart cast to 'kotlin.String' is impossible, because 'a' could have changed since the is-check">a</error>
     }
@@ -209,7 +209,7 @@ fun f(): String {
 fun foo(aa: Any): Int {
     var a = aa
     if (a is Int) {
-        return <error descr="[SMARTCAST_IMPOSSIBLE] Smart cast to 'kotlin.Int' is impossible, because 'a' could have changed since the is-check">a</error>
+        return <info descr="Smart cast to kotlin.Int">a</info>
     }
     return 1
 }

idea/testData/quickfix/typeMismatch/casts/afterSmartcastImpossible1.kt

@@ -1,10 +1,14 @@
 // "Cast expression 'a' to 'Foo'" "true"
+
 trait Foo {
     fun plus(x: Any) : Foo
 }
 
-fun foo(_a: Any): Any {
-    var a = _a
+open class MyClass {
+    public open val a: Any = "42"
+}
+
+fun MyClass.foo(): Any {
     if (a is Foo) {
         return a as Foo + a
     }

idea/testData/quickfix/typeMismatch/casts/afterSmartcastImpossible2.kt

@@ -1,10 +1,14 @@
 // "Cast expression 'a' to 'Foo'" "true"
+
 trait Foo {
     fun not() : Foo
 }
 
-fun foo(_a: Any): Any {
-    var a = _a
+open class MyClass {
+    public open val a: Any = "42"
+}
+
+fun MyClass.foo(): Any {
     if (a is Foo) {
         return !(a as Foo)
     }

idea/testData/quickfix/typeMismatch/casts/afterSmartcastImpossible3.kt

@@ -1,11 +1,15 @@
 // "Cast expression 'x' to 'Foo<*>'" "true"
+
 trait Foo<T: Number> {
-    fun foo()
+    fun bar()
 }
 
-fun bar(_x: Any) {
-    var x = _x
+open class MyClass {
+    public open val x: Any = "42"
+}
+
+fun MyClass.bar() {
     if (x is Foo<*>) {
-        (x as Foo<*>).foo()
+        (x as Foo<*>).bar()
     }
 }

idea/testData/quickfix/typeMismatch/casts/beforeSmartcastImpossible1.kt

@@ -1,10 +1,14 @@
 // "Cast expression 'a' to 'Foo'" "true"
+
 trait Foo {
     fun plus(x: Any) : Foo
 }
 
-fun foo(_a: Any): Any {
-    var a = _a
+open class MyClass {
+    public open val a: Any = "42"
+}
+
+fun MyClass.foo(): Any {
     if (a is Foo) {
         return a<caret> + a
     }

idea/testData/quickfix/typeMismatch/casts/beforeSmartcastImpossible2.kt

@@ -1,10 +1,14 @@
 // "Cast expression 'a' to 'Foo'" "true"
+
 trait Foo {
     fun not() : Foo
 }
 
-fun foo(_a: Any): Any {
-    var a = _a
+open class MyClass {
+    public open val a: Any = "42"
+}
+
+fun MyClass.foo(): Any {
     if (a is Foo) {
         return !a<caret>
     }

idea/testData/quickfix/typeMismatch/casts/beforeSmartcastImpossible3.kt

@@ -1,11 +1,15 @@
 // "Cast expression 'x' to 'Foo<*>'" "true"
+
 trait Foo<T: Number> {
-    fun foo()
+    fun bar()
 }
 
-fun bar(_x: Any) {
-    var x = _x
+open class MyClass {
+    public open val x: Any = "42"
+}
+
+fun MyClass.bar() {
     if (x is Foo<*>) {
-        x<caret>.foo()
+        x<caret>.bar()
     }
 }