More precise value reassignment analysis. #KT-7418 Fixed. #KT-6902 Fixed.

Variable can now be "exactly initialized", "may be initialized" and "not initialized".
A set of relevant tests. Some fixed tests.

compiler/testData/diagnostics/tests/reassignment/afterfor.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(k: Int): Int {
+    val i: Int
+    for (j in 1..k) {
+        <!VAL_REASSIGNMENT!>i<!> = j
+    }
+    i = 6
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/afterfor.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ k: kotlin.Int): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/dowhile.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(): Int {
+    val i: Int
+    var j = 0
+    do {
+        <!VAL_REASSIGNMENT!>i<!> = ++j
+    } while (j < 5)
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/dowhile.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/else.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(f: Boolean): Int {
+    val i: Int
+    if (f) {}
+    else {
+        i = 2
+    }
+    <!VAL_REASSIGNMENT!>i<!> = 3
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/else.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ f: kotlin.Boolean): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/foronly.kt

@@ -0,0 +1,9 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(k: Int): Int {
+    val i: Int
+    for (j in 1..k) {
+        <!VAL_REASSIGNMENT!>i<!> = j
+    }
+    return <!UNINITIALIZED_VARIABLE!>i<!>
+}

compiler/testData/diagnostics/tests/reassignment/foronly.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ k: kotlin.Int): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/if.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(f: Boolean): Int {
+    val i: Int
+    if (f) {
+        i = 1
+    }
+    <!VAL_REASSIGNMENT!>i<!> = 3
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/if.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ f: kotlin.Boolean): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/ifelse.kt

@@ -0,0 +1,13 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(f: Boolean): Int {
+    val i: Int
+    if (f) {
+        i = 1
+    }
+    else {
+        i = 2
+    }
+    <!VAL_REASSIGNMENT!>i<!> = 3
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/ifelse.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ f: kotlin.Boolean): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/noifelse.kt

@@ -0,0 +1,6 @@
+fun foo(f: Boolean): Int {
+    val i: Int
+    if (f) {}
+    i = 3
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/noifelse.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ f: kotlin.Boolean): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/when.kt

@@ -0,0 +1,10 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(f: Boolean): Int {
+    val i: Int
+    when (f) {
+        true -> i = 1
+    }
+    <!VAL_REASSIGNMENT!>i<!> = 3
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/when.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ f: kotlin.Boolean): kotlin.Int

compiler/testData/diagnostics/tests/reassignment/whiletrue.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -UNUSED_VALUE
+
+fun foo(): Int {
+    val i: Int
+    var j = 0
+    while (true) {
+        <!VAL_REASSIGNMENT!>i<!> = ++j
+        if (j > 5) break
+    } 
+    return i
+}

compiler/testData/diagnostics/tests/reassignment/whiletrue.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(): kotlin.Int