Always null detection

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

@@ -0,0 +1,11 @@
+fun foo(): String {
+    var s: String?
+    s = null
+    <!ALWAYS_NULL!>s<!>?.length
+    if (<!ALWAYS_NULL!>s<!> == null) s = "z"
+    var t: String? = "y"
+    if (t == null) t = "x"
+    var x: Int? = null
+    if (x == null) <!TYPE_MISMATCH!><!DEBUG_INFO_SMARTCAST!>x<!> += null<!>
+    return <!DEBUG_INFO_SMARTCAST!>t<!> + s
+}

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

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

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

@@ -8,19 +8,19 @@ fun foo(x : String?, y : String?) {
         x<!UNSAFE_CALL!>.<!>length
         y<!UNSAFE_CALL!>.<!>length
     }
-    if (y != null || x == y) {
+    if (y != null || x == <!ALWAYS_NULL!>y<!>) {
         x<!UNSAFE_CALL!>.<!>length
         y<!UNSAFE_CALL!>.<!>length
     }
     else {
         // y == null but x != y
         <!DEBUG_INFO_SMARTCAST!>x<!>.length
-        y<!UNSAFE_CALL!>.<!>length
+        <!ALWAYS_NULL!>y<!><!UNSAFE_CALL!>.<!>length
     }
-    if (y == null && x != y) {
+    if (y == null && x != <!ALWAYS_NULL!>y<!>) {
         // y == null but x != y
         <!DEBUG_INFO_SMARTCAST!>x<!>.length
-        y<!UNSAFE_CALL!>.<!>length
+        <!ALWAYS_NULL!>y<!><!UNSAFE_CALL!>.<!>length
     }
     else {
         x<!UNSAFE_CALL!>.<!>length

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

@@ -3,10 +3,10 @@ fun foo(x: String?, y: String?, z: String?, w: String?) {
         <!DEBUG_INFO_SMARTCAST!>z<!>.length
     else
         z<!UNSAFE_CALL!>.<!>length
-    if (x != null || y != null || (x != z && y != z))
+    if (x != null || y != null || (<!ALWAYS_NULL!>x<!> != z && <!ALWAYS_NULL!>y<!> != z))
         z<!UNSAFE_CALL!>.<!>length
     else
-        z<!UNSAFE_CALL!>.<!>length
+        <!ALWAYS_NULL!>z<!><!UNSAFE_CALL!>.<!>length
     if (x == null || y == null || (x != z && y != z))
         z<!UNSAFE_CALL!>.<!>length
     else

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

@@ -0,0 +1,10 @@
+class IncDec {
+    <!INAPPLICABLE_OPERATOR_MODIFIER!>operator<!> fun inc(): Unit {}
+}
+
+fun foo(): IncDec {
+    var x = IncDec()
+    x = <!UNUSED_CHANGED_VALUE!>x<!INC_DEC_SHOULD_NOT_RETURN_UNIT!>++<!><!>
+    x<!INC_DEC_SHOULD_NOT_RETURN_UNIT!>++<!>
+    return x
+}

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

@@ -0,0 +1,11 @@
+package
+
+public fun foo(): IncDec
+
+public final class IncDec {
+    public constructor IncDec()
+    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 operator fun inc(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -1,6 +1,6 @@
 fun bar(x: Int?): Int {
     if (x != null) return -1
-    if (<!SENSELESS_COMPARISON!>x == null<!>) return -2
+    if (<!ALWAYS_NULL!>x<!> == null) return -2
     // Should be unreachable
     return 2 + 2
 }

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

@@ -4,7 +4,7 @@ fun foo() {
     v = "abc"
     <!DEBUG_INFO_SMARTCAST!>v<!>.length
     v = null
-    v<!UNSAFE_CALL!>.<!>length
+    <!ALWAYS_NULL!>v<!><!UNSAFE_CALL!>.<!>length
     v = "abc"
     <!DEBUG_INFO_SMARTCAST!>v<!>.length
 }

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

@@ -3,5 +3,5 @@ fun foo() {
     // It is possible in principle to provide smart cast here
     v<!UNSAFE_CALL!>.<!>length
     v = null
-    v<!UNSAFE_CALL!>.<!>length
+    <!ALWAYS_NULL!>v<!><!UNSAFE_CALL!>.<!>length
 }

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

@@ -1,5 +1,5 @@
 fun foo(): Int {
     var i: Int? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>42<!>
     i = null
-    return i <!UNSAFE_INFIX_CALL!>+<!> 1
+    return <!ALWAYS_NULL!>i<!> <!UNSAFE_INFIX_CALL!>+<!> 1
 }

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

@@ -1,5 +1,5 @@
 fun foo(): Int {
     var s: String? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>"abc"<!>
     s = null
-    return s<!UNSAFE_CALL!>.<!>length
+    return <!ALWAYS_NULL!>s<!><!UNSAFE_CALL!>.<!>length
 }