Preliminary declaration visitor for estimating local variable's predictability for smart casts

Predictability estimation algorithm is completely new, but backward compatibility should present.
A large set of tests. Some updated tests.
Smart casts allowed for captured variables if they are not modified in closure #KT-9051 Fixed
Also #KT-8643 Fixed
Also #KT-7976 Fixed
Correct handling of lambda arguments in functions #KT-9143 Fixed

compiler/testData/diagnostics/tests/smartCasts/lambdaAndArgument.kt

@@ -0,0 +1,14 @@
+// !DIAGNOSTICS: -NOTHING_TO_INLINE
+
+inline fun <T> foo(t1: T, t2: T) = t1 ?: t2
+
+inline fun <T> bar(<!UNUSED_PARAMETER!>l<!>: (T) -> Unit): T = null!!
+
+fun use() {
+    var x: Int?
+    x = 5
+    // Write is AFTER
+    <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+    // x is nullable at the second argument
+    foo(bar { x = null }, x!!)
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaAndArgument.txt

@@ -0,0 +1,5 @@
+package
+
+@kotlin.inline() public fun </*0*/ T> bar(/*0*/ l: (T) -> kotlin.Unit): T
+@kotlin.inline() public fun </*0*/ T> foo(/*0*/ t1: T, /*1*/ t2: T): T
+public fun use(): kotlin.Unit

compiler/testData/diagnostics/tests/smartCasts/lambdaAndArgumentFun.kt

@@ -0,0 +1,14 @@
+// !DIAGNOSTICS: -NOTHING_TO_INLINE
+// See KT-9143: smart cast on a variable nulled inside a lambda argument
+inline fun <T> foo(t1: T, t2: T) = t1 ?: t2
+
+inline fun <T> bar(<!UNUSED_PARAMETER!>l<!>: (T) -> Unit): T = null!!
+
+fun use() {
+    var x: Int?
+    x = 5
+    // Write to x is AFTER
+    <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+    // No smart cast should be here!
+    foo(bar { x = null }, <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode())
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaAndArgumentFun.txt

@@ -0,0 +1,5 @@
+package
+
+@kotlin.inline() public fun </*0*/ T> bar(/*0*/ l: (T) -> kotlin.Unit): T
+@kotlin.inline() public fun </*0*/ T> foo(/*0*/ t1: T, /*1*/ t2: T): T
+public fun use(): kotlin.Unit

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifies.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun run(f: () -> Unit) = 0
+
+fun foo(arg: Int?) {
+    run {
+        var x = arg
+        if (x == null) return@run
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifies.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(/*0*/ arg: kotlin.Int?): kotlin.Unit
+public fun run(/*0*/ f: () -> kotlin.Unit): kotlin.Int

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesInLoop.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun run(f: () -> Unit) = 0
+
+fun foo(arg: Int?) {
+    run {
+        var x = arg
+        while (x != null) {
+            x = <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+            if (x == 0) x = null
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesInLoop.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(/*0*/ arg: kotlin.Int?): kotlin.Unit
+public fun run(/*0*/ f: () -> kotlin.Unit): kotlin.Int

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesInSecondary.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun run(f: () -> Unit) = 0
+
+class My {
+    constructor(arg: Int?) {
+        run {
+            var x = arg
+            if (x == null) return@run
+            <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+        }   
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesInSecondary.txt

@@ -0,0 +1,10 @@
+package
+
+public fun run(/*0*/ f: () -> kotlin.Unit): kotlin.Int
+
+public final class My {
+    public constructor My(/*0*/ arg: kotlin.Int?)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesWithDirectEq.kt

@@ -0,0 +1,22 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun run(f: () -> Unit) = 0
+
+fun foo(arg: Int?) = run {
+    var x = arg
+    if (x == null) return@run
+    <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+}
+
+class My {
+    fun foo(arg: Int?) = run {
+        var x = arg
+        if (x == null) return@run
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+    }
+
+    fun Int?.bar() = run {
+        var x = this
+        if (x == null) return@run
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaDeclaresAndModifiesWithDirectEq.txt

@@ -0,0 +1,13 @@
+package
+
+public fun foo(/*0*/ arg: kotlin.Int?): kotlin.Int
+public fun run(/*0*/ f: () -> kotlin.Unit): kotlin.Int
+
+public final class My {
+    public constructor My()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun foo(/*0*/ arg: kotlin.Int?): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    public final fun kotlin.Int?.bar(): kotlin.Int
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaUsesOwnerModifies.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun run(f: () -> Unit) = 0
+
+fun foo(arg: Int?) {
+    var x = arg
+    if (x == null) return
+    run {
+        // Not safe: x = null later in the owner
+        x<!UNSAFE_CALL!>.<!>hashCode()
+    }
+    x = null  
+}

compiler/testData/diagnostics/tests/smartCasts/lambdaUsesOwnerModifies.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(/*0*/ arg: kotlin.Int?): kotlin.Unit
+public fun run(/*0*/ f: () -> kotlin.Unit): kotlin.Int

compiler/testData/diagnostics/tests/smartCasts/localClassChanges.kt

@@ -0,0 +1,15 @@
+fun trans(n: Int, f: () -> Boolean) = if (f()) n else null
+
+fun foo() {
+    var i: Int? = 5    
+    if (i != null) {
+        class Changing {
+            fun bar() {
+                i = null
+            }
+        }
+        i<!UNSAFE_CALL!>.<!>hashCode()
+        Changing().bar()
+        i<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/localClassChanges.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Unit
+public fun trans(/*0*/ n: kotlin.Int, /*1*/ f: () -> kotlin.Boolean): kotlin.Int?

compiler/testData/diagnostics/tests/smartCasts/localFunBetween.kt

@@ -0,0 +1,15 @@
+open class Base
+class Derived: Base()
+
+fun bar(derived: Derived) = derived
+
+fun trans(n: Int, f: (Int) -> Boolean) = if (f(n)) n else null
+
+fun foo() {
+    val base: Base = Derived()
+    if (base is Derived) {
+        fun can(n: Int) = n > 0
+        trans(42, ::can)
+        bar(<!DEBUG_INFO_SMARTCAST!>base<!>)
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/localFunBetween.txt

@@ -0,0 +1,19 @@
+package
+
+public fun bar(/*0*/ derived: Derived): Derived
+public fun foo(): kotlin.Unit
+public fun trans(/*0*/ n: kotlin.Int, /*1*/ f: (kotlin.Int) -> kotlin.Boolean): kotlin.Int?
+
+public open class Base {
+    public constructor Base()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Derived : Base {
+    public constructor Derived()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/localFunChanges.kt

@@ -0,0 +1,14 @@
+fun trans(n: Int, f: () -> Boolean) = if (f()) n else null
+
+fun foo() {
+    var i: Int? = 5    
+    if (i != null) {
+        fun can(): Boolean {
+            i = null
+            return true
+        }
+        i<!UNSAFE_CALL!>.<!>hashCode()
+        trans(<!TYPE_MISMATCH!>i<!>, ::can)
+        i<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/localFunChanges.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Unit
+public fun trans(/*0*/ n: kotlin.Int, /*1*/ f: () -> kotlin.Boolean): kotlin.Int?

compiler/testData/diagnostics/tests/smartCasts/localObjectChanges.kt

@@ -0,0 +1,15 @@
+fun trans(n: Int, f: () -> Boolean) = if (f()) n else null
+
+fun foo() {
+    var i: Int? = 5    
+    if (i != null) {
+        // Write is AFTER this place
+        <!DEBUG_INFO_SMARTCAST!>i<!>.hashCode()
+        object {
+            fun bar() {
+                i = null
+            }
+        }.bar()
+        i<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/localObjectChanges.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Unit
+public fun trans(/*0*/ n: kotlin.Int, /*1*/ f: () -> kotlin.Boolean): kotlin.Int?

compiler/testData/diagnostics/tests/smartCasts/ownerDeclaresBothModifies.kt

@@ -0,0 +1,15 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+fun run(f: () -> Unit) = 0
+
+fun foo(arg: Int?) {
+    var x = arg
+    if (x == null) return
+    run {
+        // Unsafe because of owner modification
+        x<!UNSAFE_CALL!>.<!>hashCode()
+        x = null
+    }
+    if (x != null) x = 42
+    // Unsafe because of lambda
+    x<!UNSAFE_CALL!>.<!>hashCode()
+}

compiler/testData/diagnostics/tests/smartCasts/ownerDeclaresBothModifies.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(/*0*/ arg: kotlin.Int?): kotlin.Unit
+public fun run(/*0*/ f: () -> kotlin.Unit): kotlin.Int

compiler/testData/diagnostics/tests/smartCasts/varChangedInInitializer.kt

@@ -0,0 +1,7 @@
+class My {
+    init {
+        var y: Int?
+        y = 42
+        <!DEBUG_INFO_SMARTCAST!>y<!>.hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/varChangedInInitializer.txt

@@ -0,0 +1,8 @@
+package
+
+public final class My {
+    public constructor My()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/varChangedInLocalInitializer.kt

@@ -0,0 +1,10 @@
+fun foo() {
+    class My {
+        val x: Int
+        init {
+            var y: Int?
+            y = 42
+            x = <!DEBUG_INFO_SMARTCAST!>y<!>.hashCode()
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/varChangedInLocalInitializer.txt

@@ -0,0 +1,3 @@
+package
+
+public fun foo(): kotlin.Unit

compiler/testData/diagnostics/tests/smartCasts/varInAccessor.kt

@@ -0,0 +1,17 @@
+var x: Int = 0
+    get() {
+        var y: Int? = null
+        if (y != null) {
+            return <!DEBUG_INFO_SMARTCAST!>y<!>.hashCode()
+        }
+        return field
+    }
+    set(param) {
+        var y: Int? = null
+        if (y != null) {
+            field = <!DEBUG_INFO_SMARTCAST!>y<!>.hashCode()
+        }
+        else {
+            field = param
+        }
+    }

compiler/testData/diagnostics/tests/smartCasts/varInAccessor.txt

@@ -0,0 +1,3 @@
+package
+
+public var x: kotlin.Int

compiler/testData/diagnostics/tests/smartCasts/varInInitializer.kt

@@ -0,0 +1,12 @@
+class My {
+    val x: Int
+    init {
+        var y: Int? = null
+        if (y != null) {
+            x = <!DEBUG_INFO_SMARTCAST!>y<!>.hashCode()
+        }
+        else {
+            x = 0
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/varInInitializer.txt

@@ -0,0 +1,9 @@
+package
+
+public final class My {
+    public constructor My()
+    public final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/varInSecondaryConstructor.kt

@@ -0,0 +1,10 @@
+class My(val z: Int) {
+    var x: Int = 0
+    constructor(arg: Int?): this(arg ?: 42) {
+        var y: Int?
+        y = arg
+        if (y != null) {
+            x = <!DEBUG_INFO_SMARTCAST!>y<!>
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/varInSecondaryConstructor.txt

@@ -0,0 +1,11 @@
+package
+
+public final class My {
+    public constructor My(/*0*/ z: kotlin.Int)
+    public constructor My(/*0*/ arg: kotlin.Int?)
+    public final var x: kotlin.Int
+    public final val z: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/varInsideLocalFun.kt

@@ -0,0 +1,17 @@
+// Based on KT-8643
+public class MyClass
+{
+    fun main() {
+        var str: String? = null
+
+        if (str != null)
+            callback {
+                // Nodoby writes str, smart cast is possible
+                method1(<!DEBUG_INFO_SMARTCAST!>str<!>)
+            }
+    }
+
+    inline fun callback(foo: () ->Unit) = foo()
+
+    fun method1(str: String) = str
+}

compiler/testData/diagnostics/tests/smartCasts/varInsideLocalFun.txt

@@ -0,0 +1,11 @@
+package
+
+public final class MyClass {
+    public constructor MyClass()
+    @kotlin.inline() public final fun callback(/*0*/ foo: () -> kotlin.Unit): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final fun main(): kotlin.Unit
+    public final fun method1(/*0*/ str: kotlin.String): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/variables/accessorAndFunction.kt

@@ -0,0 +1,23 @@
+class My {
+
+    val y: Int 
+        get() {
+            var x: Int?
+            x = 3
+            return <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+        }
+
+    fun test() {
+        var x: Int?
+        x = 2
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+        fun bb() {
+           var <!NAME_SHADOWING!>x<!>: Any?
+           x = 4
+           <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
+        }
+        x = 4
+        // Really smart cast is possible but name shadowing by bb() prevents it
+        <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/variables/accessorAndFunction.txt

@@ -0,0 +1,10 @@
+package
+
+public final class My {
+    public constructor My()
+    public final val y: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final fun test(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/variables/inPropertySam.kt

@@ -0,0 +1,18 @@
+// FILE: My.java
+
+public interface My {
+    String foo(String arg);
+}
+
+// FILE: test.kt
+
+class Your {
+    val x = My() {
+        arg: String? ->
+        var y = arg
+        val z: String
+        if (y != null) z = <!DEBUG_INFO_SMARTCAST!>y<!>
+        else z = "42"
+        z
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/variables/inPropertySam.txt

@@ -0,0 +1,18 @@
+package
+
+public /*synthesized*/ fun My(/*0*/ function: (kotlin.String!) -> kotlin.String!): My
+
+public interface My {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(/*0*/ arg: kotlin.String!): kotlin.String!
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Your {
+    public constructor Your()
+    public final val x: My
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/smartCasts/variables/lambdaBetweenArguments.kt

@@ -0,0 +1,9 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun foo(x: Int, f: () -> Unit, y: Int) {}
+
+fun bar() {
+    var x: Int?
+    x = 4
+    foo(<!DEBUG_INFO_SMARTCAST!>x<!>, { x = null; x<!UNSAFE_CALL!>.<!>hashCode() }, <!SMARTCAST_IMPOSSIBLE!>x<!>)
+}

compiler/testData/diagnostics/tests/smartCasts/variables/lambdaBetweenArguments.txt

@@ -0,0 +1,4 @@
+package
+
+public fun bar(): kotlin.Unit
+public fun foo(/*0*/ x: kotlin.Int, /*1*/ f: () -> kotlin.Unit, /*2*/ y: kotlin.Int): kotlin.Unit

compiler/testData/diagnostics/tests/smartCasts/varnotnull/varCapturedInSafeClosure.kt

@@ -9,7 +9,7 @@ public fun foo() {
     }
     if (s != null) {
         System.out.println(closure())
-        // Smart cast is possible but closure makes it harder to understand
-        System.out.println(s<!UNSAFE_CALL!>.<!>length)
+        // Smart cast is possible, nobody modifies s
+        System.out.println(<!DEBUG_INFO_SMARTCAST!>s<!>.length)
     }
 }