FIR DFA: check for reassignments of LHS when handling ?..

`x?.y != null` does not imply that `x != null` if e.g. an argument to `y` has reassigned `x` in the meantime. The same is true for `x == y` and `functionWithContract(x, y)`, but those are somewhat harder to implement since there is no easy way to find the last node of a certain argument. ^KT-55096
2022-11-14 20:45:18 +01:00
parent ae1048f8a9
commit 5cc08fb314
11 changed files with 164 additions and 22 deletions
@@ -0,0 +1,51 @@
+// ISSUE: KT-55096
+// SKIP_TXT
+
+import kotlin.contracts.*
+
+class C(val x: Int)
+
+@OptIn(ExperimentalContracts::class)
+fun isNotNullAlsoCall(a: String?, b: () -> Unit): Boolean {
+    contract {
+        returns(true) implies (a != null)
+        callsInPlace(b, InvocationKind.EXACTLY_ONCE)
+    }
+    b()
+    return a != null
+}
+
+fun binaryBooleanExpression() {
+    var x: String? = ""
+    if (x is String || (x is String).also { x = null }) {
+        x<!UNSAFE_CALL!>.<!>length // bad (x#0 is String, x#1 is Nothing?, this is either)
+    }
+}
+
+fun unoverriddenEquals(a: Any?) {
+    val c = C(1)
+    var b: Any?
+    b = c
+    if (b == c.also { b = a }) {
+        a.x // bad (b#0 is C, b#1 = a)
+        b.x // bad (b#0 is C, this is b#1)
+        if (<!USELESS_IS_CHECK!>b is C<!>) { // b#1
+            a.x // ok (b#1 = a)
+            b.x // ok
+        }
+    }
+}
+
+fun safeCall() {
+    var x: String? = ""
+    if (x?.let { x = null; 1 } != null) {
+        x<!UNSAFE_CALL!>.<!>length // bad (#2 != null => x#0 != null; but x#1 = null and this is either)
+    }
+}
+
+fun contractFunction() {
+    var x: String? = ""
+    if (isNotNullAlsoCall(x) { x = null }) {
+        x.length // bad (#2 == true => x#0 != null; but this is x#1 = null)
+    }
+}
@@ -0,0 +1,51 @@
+// ISSUE: KT-55096
+// SKIP_TXT
+
+import kotlin.contracts.*
+
+class C(val x: Int)
+
+@OptIn(ExperimentalContracts::class)
+fun isNotNullAlsoCall(a: String?, b: () -> Unit): Boolean {
+    contract {
+        returns(true) implies (a != null)
+        callsInPlace(b, InvocationKind.EXACTLY_ONCE)
+    }
+    b()
+    return a != null
+}
+
+fun binaryBooleanExpression() {
+    var x: String? = ""
+    if (x is String || (x is String).also { x = null }) {
+        x<!UNSAFE_CALL!>.<!>length // bad (x#0 is String, x#1 is Nothing?, this is either)
+    }
+}
+
+fun unoverriddenEquals(a: Any?) {
+    val c = C(1)
+    var b: Any?
+    b = c
+    if (b == c.also { b = a }) {
+        a.<!UNRESOLVED_REFERENCE!>x<!> // bad (b#0 is C, b#1 = a)
+        <!SMARTCAST_IMPOSSIBLE!>b<!>.x // bad (b#0 is C, this is b#1)
+        if (b is C) { // b#1
+            a.<!UNRESOLVED_REFERENCE!>x<!> // ok (b#1 = a)
+            <!SMARTCAST_IMPOSSIBLE!>b<!>.x // ok
+        }
+    }
+}
+
+fun safeCall() {
+    var x: String? = ""
+    if (x?.let { x = null; 1 } != null) {
+        <!SMARTCAST_IMPOSSIBLE!>x<!>.length // bad (#2 != null => x#0 != null; but x#1 = null and this is either)
+    }
+}
+
+fun contractFunction() {
+    var x: String? = ""
+    if (isNotNullAlsoCall(x) { x = null }) {
+        <!SMARTCAST_IMPOSSIBLE!>x<!>.length // bad (#2 == true => x#0 != null; but this is x#1 = null)
+    }
+}