FIR/UAST: commonize if expression

plugins/uast-kotlin-fir/testData/declaration/if.kt

@@ -0,0 +1,6 @@
+fun test(b: Boolean): Any {
+    return if (b)
+        42
+    else
+        "42"
+}

plugins/uast-kotlin-fir/testData/declaration/if.log.fe10.txt

@@ -0,0 +1,11 @@
+UFile (package = )
+    UClass (name = IfKt)
+        UMethod (name = test)
+            UParameter (name = b)
+                UAnnotation (fqName = org.jetbrains.annotations.NotNull)
+            UBlockExpression
+                UReturnExpression
+                    UIfExpression
+                        USimpleNameReferenceExpression (identifier = b)
+                        ULiteralExpression (value = 42)
+                        ULiteralExpression (value = "42")

plugins/uast-kotlin-fir/testData/declaration/if.log.fir.txt

@@ -0,0 +1,10 @@
+UFile (package = )
+    UClass (name = IfKt)
+        UMethod (name = test)
+            UParameter (name = b)
+            UBlockExpression
+                UReturnExpression
+                    UIfExpression
+                        [!] UnknownKotlinExpression (REFERENCE_EXPRESSION)
+                        ULiteralExpression (value = "not-yet-compile-time-constant")
+                        ULiteralExpression (value = "42")

plugins/uast-kotlin-fir/testData/declaration/if.render.fe10.txt

@@ -0,0 +1,5 @@
+public final class IfKt {
+    public static final fun test(@org.jetbrains.annotations.NotNull b: boolean) : java.lang.Object {
+        return if (b) 42 else "42"
+    }
+}

plugins/uast-kotlin-fir/testData/declaration/if.render.fir.txt

@@ -0,0 +1,5 @@
+public final class IfKt {
+    public static final fun test(b: boolean) : java.lang.Object {
+        return if ([!] UnknownKotlinExpression (REFERENCE_EXPRESSION)) "not-yet-compile-time-constant" else "42"
+    }
+}