Effects: add diagnostic tests on contracts

- Make AbstractDiagnosticsTest dump function contracts
- Add diagnostics tests on parsing contracts
- Add diagnostics tests on smartcats in presence of functions with
contracts
- Add diagnostics tests on initialization and flow in presence of
in-place called lambdas

==========
Introduction of EffectSystem: 16/18

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/multieffect/implicitIff.kt

@@ -0,0 +1,86 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun onlyTrue(b: Boolean): Boolean {
+    contract {
+        returns(true) implies (b)
+    }
+    return b
+}
+
+fun onlyFalse(b: Boolean): Boolean {
+    contract {
+        returns(false) implies (!b)
+    }
+    return b
+}
+
+fun trueAndFalse(b: Boolean): Boolean {
+    contract {
+        returns(true) implies (b)
+        returns(false) implies (!b)
+    }
+    return b
+}
+
+
+
+// ==== actual tests ====
+
+fun useOnlyTrueInTrueBranch(x: Any?) {
+    if (onlyTrue(x is String)) {
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+    else {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+}
+
+fun useOnlyTrueInFalseBranch(x: Any?) {
+    if (onlyTrue(x !is String)) {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    else {
+        // No smartcast here, we don't know that condition is false here
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+}
+
+fun useOnlyFalseInTrueBranch(x: Any?) {
+    if (onlyFalse(x is String)) {
+        // No smartcast here, we don't know that condition is true here
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    else {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+}
+
+fun useOnlyFalseInFalseBranch(x: Any?) {
+    if (onlyFalse(x !is String)) {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    else {
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+}
+
+fun useTrueAndFalseInTrueBranch(x: Any?) {
+    if (trueAndFalse(x is String)) {
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+    else {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+}
+
+fun useTrueAndFalseInFalseBranch(x: Any?) {
+    if (trueAndFalse(x !is String)) {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    else {
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/multieffect/implicitIff.txt

@@ -0,0 +1,18 @@
+package
+
+public fun onlyFalse(/*0*/ b: kotlin.Boolean): kotlin.Boolean
+    Returns(FALSE) -> !b
+
+public fun onlyTrue(/*0*/ b: kotlin.Boolean): kotlin.Boolean
+    Returns(TRUE) -> b
+
+public fun trueAndFalse(/*0*/ b: kotlin.Boolean): kotlin.Boolean
+    Returns(TRUE) -> b
+    Returns(FALSE) -> !b
+
+public fun useOnlyFalseInFalseBranch(/*0*/ x: kotlin.Any?): kotlin.Unit
+public fun useOnlyFalseInTrueBranch(/*0*/ x: kotlin.Any?): kotlin.Unit
+public fun useOnlyTrueInFalseBranch(/*0*/ x: kotlin.Any?): kotlin.Unit
+public fun useOnlyTrueInTrueBranch(/*0*/ x: kotlin.Any?): kotlin.Unit
+public fun useTrueAndFalseInFalseBranch(/*0*/ x: kotlin.Any?): kotlin.Unit
+public fun useTrueAndFalseInTrueBranch(/*0*/ x: kotlin.Any?): kotlin.Unit

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/multieffect/returnsAndCalls.kt

@@ -0,0 +1,67 @@
+// !LANGUAGE: +CallsInPlaceEffect +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun callsAndInverts(b: Boolean, block: () -> Unit): Boolean {
+    contract {
+        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
+        returns(true) implies (!b)
+        returns(false) implies b
+    }
+
+    block()
+    return !b
+}
+
+
+
+fun smartcastAndInitialization(x: Any?) {
+    val y: Int
+
+    if (callsAndInverts(x !is String) { y = 42 }) {
+        println(y)
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    } else {
+        println(y)
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    println(y)
+}
+
+fun inPresenceOfLazy(x: Any?, unknownBoolean: Boolean) {
+    val y: Int
+
+    if (unknownBoolean && callsAndInverts(x !is String) { y = 42 }) {
+        println(<!UNINITIALIZED_VARIABLE!>y<!>)
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+    else {
+        println(y)
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    println(y)
+}
+
+fun isPresenceOfLazy2(x: Any?, unknownBoolean: Boolean) {
+    val y: Int
+    if (unknownBoolean && callsAndInverts(x !is String) { y = 42 }) {
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+    else {
+        println(<!UNINITIALIZED_VARIABLE!>y<!>)
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    println(y)
+}
+
+fun isPresenceOfLazy3(x: Any?, unknownBoolean: Boolean) {
+    val y: Int
+    if (unknownBoolean && callsAndInverts(x !is String) { y = 42 }) {
+        <!DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+    else {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+    println(<!UNINITIALIZED_VARIABLE!>y<!>)
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/multieffect/returnsAndCalls.txt

@@ -0,0 +1,11 @@
+package
+
+public fun callsAndInverts(/*0*/ b: kotlin.Boolean, /*1*/ block: () -> kotlin.Unit): kotlin.Boolean
+    CallsInPlace(block, EXACTLY_ONCE)
+    Returns(TRUE) -> !b
+    Returns(FALSE) -> b
+
+public fun inPresenceOfLazy(/*0*/ x: kotlin.Any?, /*1*/ unknownBoolean: kotlin.Boolean): kotlin.Unit
+public fun isPresenceOfLazy2(/*0*/ x: kotlin.Any?, /*1*/ unknownBoolean: kotlin.Boolean): kotlin.Unit
+public fun isPresenceOfLazy3(/*0*/ x: kotlin.Any?, /*1*/ unknownBoolean: kotlin.Boolean): kotlin.Unit
+public fun smartcastAndInitialization(/*0*/ x: kotlin.Any?): kotlin.Unit