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/dsl/errors/booleanComparisons.kt

@@ -0,0 +1,22 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun foo(b: Boolean): Boolean {
+    contract {
+        // pointless, can be reduced to just "b"
+        returns(true) implies (<!ERROR_IN_CONTRACT_DESCRIPTION(only equality comparisons with 'null' allowed)!>b == true<!>)
+    }
+
+    return b
+}
+
+fun bar(b: Boolean?): Boolean {
+    contract {
+        // not pointless, but not supported yet
+        returns(true) implies (<!ERROR_IN_CONTRACT_DESCRIPTION(only equality comparisons with 'null' allowed)!>b == true<!>)
+    }
+    if (b == null) throw java.lang.IllegalArgumentException("")
+    return <!DEBUG_INFO_SMARTCAST!>b<!>
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/booleanComparisons.txt

@@ -0,0 +1,4 @@
+package
+
+public fun bar(/*0*/ b: kotlin.Boolean?): kotlin.Boolean
+public fun foo(/*0*/ b: kotlin.Boolean): kotlin.Boolean

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/callInContractDescription.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun bar(x: Int): Boolean = x == 0
+
+fun foo(x: Int): Boolean {
+    contract {
+        returns(true) implies (<!ERROR_IN_CONTRACT_DESCRIPTION(call-expressions are not supported yet)!>bar(x)<!>)
+    }
+    return x == 0
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/callInContractDescription.txt

@@ -0,0 +1,4 @@
+package
+
+public fun bar(/*0*/ x: kotlin.Int): kotlin.Boolean
+public fun foo(/*0*/ x: kotlin.Int): kotlin.Boolean

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/nestedConditionalEffects.kt

@@ -0,0 +1,10 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun foo(boolean: Boolean) {
+    contract {
+        (returns() implies (boolean)) <!UNRESOLVED_REFERENCE!>implies<!> (!boolean)
+    }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/nestedConditionalEffects.txt

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

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/notFirstStatement.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun foo(y: Boolean) {
+    val <!UNUSED_VARIABLE!>x<!>: Int = 42
+    <!CONTRACT_NOT_ALLOWED!>contract {
+        returns() implies y
+    }<!>
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/notFirstStatement.txt

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

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/referenceToProperty.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+class Foo(val x: Int?) {
+    fun isXNull(): Boolean {
+        contract {
+            returns(false) implies (<!ERROR_IN_CONTRACT_DESCRIPTION(only references to parameters are allowed in contract description)!>x<!> != null)
+        }
+        return x != null
+    }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/referenceToProperty.txt

@@ -0,0 +1,10 @@
+package
+
+public final class Foo {
+    public constructor Foo(/*0*/ x: kotlin.Int?)
+    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 final fun isXNull(): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/unlabeledReceiver.kt

@@ -0,0 +1,11 @@
+// !LANGUAGE: +ReturnsEffect
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+
+import kotlin.internal.contracts.*
+
+fun Any?.foo(): Boolean {
+    contract {
+        returns(true) implies (<!ERROR_IN_CONTRACT_DESCRIPTION(only references to parameters are allowed. Did you miss label on <this>?)!>this<!> <!EQUALS_MISSING!>!=<!> null)
+    }
+    return this != null
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/dsl/errors/unlabeledReceiver.txt

@@ -0,0 +1,4 @@
+package
+
+public fun kotlin.Any?.foo(): kotlin.Boolean
+    Returns(TRUE) -> <this> != null