KT-16553 Underscore variable values shall not be evaluated

Do not generate 'componentN' calls for '_' in destructuring assignment.

Author: dnpetrov

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/StatementGenerator.kt

@@ -114,6 +114,10 @@ class StatementGenerator(
             componentSubstitutedCall.setExplicitReceiverValue(containerValue)
 
             val componentVariable = getOrFail(BindingContext.VARIABLE, ktEntry)
+
+            // componentN for '_' SHOULD NOT be evaluated
+            if (componentVariable.name.isSpecial) continue
+
             val irComponentCall = callGenerator.generateCall(ktEntry.startOffset, ktEntry.endOffset, componentSubstitutedCall,
                                                              IrStatementOrigin.COMPONENT_N.withIndex(index + 1))
             val irComponentVar = IrVariableImpl(ktEntry.startOffset, ktEntry.endOffset, IrDeclarationOrigin.DEFINED,

compiler/testData/ir/irText/expressions/destructuringWithUnderscore.kt

@@ -0,0 +1,11 @@
+object A
+
+object B {
+    operator fun A.component1() = 1
+    operator fun A.component2() = 2
+    operator fun A.component3() = 3
+}
+
+fun B.test() {
+    val (x, _, z) = A
+}

compiler/testData/ir/irText/expressions/destructuringWithUnderscore.txt

@@ -0,0 +1,36 @@
+FILE /destructuringWithUnderscore.kt
+  CLASS OBJECT A
+    CONSTRUCTOR private constructor A()
+      BLOCK_BODY
+        DELEGATING_CONSTRUCTOR_CALL 'constructor Any()'
+        INSTANCE_INITIALIZER_CALL classDescriptor='A'
+  CLASS OBJECT B
+    CONSTRUCTOR private constructor B()
+      BLOCK_BODY
+        DELEGATING_CONSTRUCTOR_CALL 'constructor Any()'
+        INSTANCE_INITIALIZER_CALL classDescriptor='B'
+    FUN public final operator fun A.component1(): kotlin.Int
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='component1() on A: Int'
+          CONST Int type=kotlin.Int value='1'
+    FUN public final operator fun A.component2(): kotlin.Int
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='component2() on A: Int'
+          CONST Int type=kotlin.Int value='2'
+    FUN public final operator fun A.component3(): kotlin.Int
+      BLOCK_BODY
+        RETURN type=kotlin.Nothing from='component3() on A: Int'
+          CONST Int type=kotlin.Int value='3'
+  FUN public fun B.test(): kotlin.Unit
+    BLOCK_BODY
+      COMPOSITE type=kotlin.Unit origin=DESTRUCTURING_DECLARATION
+        VAR IR_TEMPORARY_VARIABLE val tmp0_container: A
+          GET_OBJECT 'A' type=A
+        VAR val x: kotlin.Int
+          CALL 'component1() on A: Int' type=kotlin.Int origin=COMPONENT_N(index=1)
+            $this: GET_VAR '<receiver: test() on B: Unit>' type=B origin=null
+            $receiver: GET_VAR 'tmp0_container: A' type=A origin=null
+        VAR val z: kotlin.Int
+          CALL 'component3() on A: Int' type=kotlin.Int origin=COMPONENT_N(index=3)
+            $this: GET_VAR '<receiver: test() on B: Unit>' type=B origin=null
+            $receiver: GET_VAR 'tmp0_container: A' type=A origin=null

compiler/tests/org/jetbrains/kotlin/ir/IrTextTestCaseGenerated.java

@@ -482,6 +482,12 @@ public void testDestructuring1() throws Exception {
             doTest(fileName);
         }
 
+        @TestMetadata("destructuringWithUnderscore.kt")
+        public void testDestructuringWithUnderscore() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/ir/irText/expressions/destructuringWithUnderscore.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("dotQualified.kt")
         public void testDotQualified() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/ir/irText/expressions/dotQualified.kt");