KT-34644 Give return keyword more priority in completion where appropriate

- See `returnExpressionItems::returnIsProbableInPosition` to get an idea where return is supposed to be more appropriate
  - End of the block (except for top level block of unit function or cycle) or as single expression in if or when
  - Right side of the elvis operator (which is not already in return)
- Add additional `probable_keyword` weigher to signalize about probable keyword (for now it is only for `return`)
- ^KT-34644 Fixed

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/BeginOfNestedBlock.kt

@@ -0,0 +1,11 @@
+fun returnFun() {}
+
+fun usage() {
+    if (true) {
+        re<caret>
+        return
+    }
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/BeginOfTopLevelBlock.kt

@@ -0,0 +1,9 @@
+fun returnFun() {}
+
+fun usage() {
+    re<caret>
+    return
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/EndOfNestedBlock.kt

@@ -0,0 +1,10 @@
+fun returnFun() {}
+
+fun usage() {
+    if (true) {
+        re<caret>
+    }
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/EndOfTopLevelBlock.kt

@@ -0,0 +1,8 @@
+fun returnFun() {}
+
+fun usage() {
+    re<caret>
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/ForWithBody.kt

@@ -0,0 +1,10 @@
+fun returnFun() {}
+
+fun usage() {
+    for (i in 1..10) {
+        re<caret>
+    }
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/ForWithoutBody.kt

@@ -0,0 +1,8 @@
+fun returnFun() {}
+
+fun usage() {
+    for (i in 1..10) re<caret>
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/IfWithoutBody.kt

@@ -0,0 +1,8 @@
+fun returnFun() {}
+
+fun usage() {
+    if (true) re<caret>
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/InElvis.kt

@@ -0,0 +1,9 @@
+fun returnFun() {}
+
+fun usage(a: Int?) {
+    a ?: re<caret>
+    return
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/InElvisWhenSmartCompletionWins.kt

@@ -0,0 +1,12 @@
+fun returnFun(): Int = 10
+fun <T> returnAnything(): T = null!!
+
+fun usage(a: Int?) {
+    a ?: re<caret>
+}
+
+// function of the same type as `a` is preferred to return in this case
+
+// ORDER: returnFun
+// ORDER: return
+// ORDER: returnAnything

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/InWhenSingleExpression.kt

@@ -0,0 +1,11 @@
+fun returnFun() {}
+
+fun usage(a: Int) {
+    when (a) {
+        10 -> re<caret>
+    }
+    return
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/noReturnType/InWhenWithBody.kt

@@ -0,0 +1,13 @@
+fun returnFun() {}
+
+fun usage(a: Int) {
+    when (a) {
+        10 -> {
+            re<caret>
+        }
+    }
+    return
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/BeginOfNestedBlock.kt

@@ -0,0 +1,13 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    if (true) {
+        re<caret>
+        return 20
+    }
+
+    return 10
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/BeginOfTopLevelBlock.kt

@@ -0,0 +1,9 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    re<caret>
+    return 10
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/EndOfNestedBlock.kt

@@ -0,0 +1,12 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    if (true) {
+        re<caret>
+    }
+
+    return 10
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/EndOfTopLevelBlock.kt

@@ -0,0 +1,8 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    re<caret>
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/ForWithBody.kt

@@ -0,0 +1,12 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    for (i in 1..10) {
+        re<caret>
+    }
+
+    return 10
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/ForWithoutBody.kt

@@ -0,0 +1,10 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    for (i in 1..10) re<caret>
+
+    return 10
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/IfWithoutBody.kt

@@ -0,0 +1,10 @@
+fun returnFun(): Int = 10
+
+fun usage(): Int {
+    if (true) re<caret>
+
+    return 10
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InElvis.kt

@@ -0,0 +1,9 @@
+fun returnFun() {}
+
+fun usage(a: Int?): Int {
+    a ?: re<caret>
+    return 10
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InElvisInReturn.kt

@@ -0,0 +1,8 @@
+fun reportError(): Nothing
+
+fun usage(a: Int?): Int {
+    return a ?: a ?: a ?: re<caret>
+}
+
+// ORDER: reportError
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InElvisWhenSmartCompletionWins.kt

@@ -0,0 +1,13 @@
+fun returnFun(): Int = 10
+fun <T> returnAnything(): T = null!!
+
+fun usage(a: Int?): Int {
+    a ?: re<caret>
+    return 10
+}
+
+// function of the same type as `a` is preferred to return in this case
+
+// ORDER: returnFun
+// ORDER: return
+// ORDER: returnAnything

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InIfAsReturnedExpression.kt

@@ -0,0 +1,8 @@
+fun reportError(): Nothing
+
+fun usage(a: Int?): Int {
+    return if (a == null) re<caret> else a
+}
+
+// ORDER: reportError
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InIfInWhenWithBodyAsReturnedExpression.kt

@@ -0,0 +1,16 @@
+fun reportError(): Nothing
+
+fun usage(a: Int?): Int {
+    return when {
+        a == null -> {
+            if (true) { re<caret> }
+
+            10
+        }
+
+        else -> a
+    }
+}
+
+// ORDER: return
+// ORDER: reportError

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InNotElvisBinaryOperator.kt

@@ -0,0 +1,9 @@
+fun returnFun(): String = ""
+
+fun usage(a: Int?): Int {
+    a to re<caret>
+    return 10
+}
+
+// ORDER: returnFun
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InWhenAsReturnedExpression.kt

@@ -0,0 +1,11 @@
+fun reportError(): Nothing
+
+fun usage(a: Int?): Int {
+    return when {
+        a == null -> re<caret>
+        else -> a
+    }
+}
+
+// ORDER: reportError
+// ORDER: return

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InWhenSingleExpression.kt

@@ -0,0 +1,11 @@
+fun returnFun(): Int = 10
+
+fun usage(a: Int): Int {
+    when (a) {
+        10 -> re<caret>
+    }
+    return 10
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InWhenWithBody.kt

@@ -0,0 +1,13 @@
+fun returnFun(): Int = 10
+
+fun usage(a: Int): Int {
+    when (a) {
+        10 -> {
+            re<caret>
+        }
+    }
+    return 10
+}
+
+// ORDER: return
+// ORDER: returnFun

idea/idea-completion/testData/weighers/basic/contextualReturn/withReturnType/InWhenWithBodyAsReturnedExpression.kt

@@ -0,0 +1,11 @@
+fun reportError(): Nothing
+
+fun usage(a: Int?): Int {
+    return when {
+        a == null -> re<caret>
+        else -> a
+    }
+}
+
+// ORDER: reportError
+// ORDER: return