Remove duplicate parameter null checks in JvmStatic delegate methods.

Remove unnecessary non-null parameter checks inside static delegate methods
created for @JvmStatic companion object methods. Allows function generation
strategy decide if such checks need to be injected.

 #KT-7188 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/FunctionCodegen.java

@@ -558,7 +558,7 @@ public class FunctionCodegen {
             mv.visitLabel(methodEntry);
             context.setMethodStartLabel(methodEntry);
 
-            if (!KotlinTypeMapper.isAccessor(functionDescriptor)) {
+            if (!strategy.skipNotNullAssertionsForParameters()) {
                 genNotNullAssertionsForParameters(new InstructionAdapter(mv), parentCodegen.state, functionDescriptor, frameMap);
             }
 
@@ -1383,6 +1383,11 @@ public class FunctionCodegen {
 
                         iv.areturn(delegateMethod.getReturnType());
                     }
+
+                    @Override
+                    public boolean skipNotNullAssertionsForParameters() {
+                        return false;
+                    }
                 }
         );
     }

compiler/backend/src/org/jetbrains/kotlin/codegen/FunctionGenerationStrategy.java

@@ -34,6 +34,8 @@ public abstract class FunctionGenerationStrategy {
             @NotNull MemberCodegen<?> parentCodegen
     );
 
+    public abstract boolean skipNotNullAssertionsForParameters();
+
     public MethodVisitor wrapMethodVisitor(@NotNull MethodVisitor mv, int access, @NotNull String name, @NotNull String desc) {
         return mv;
     }
@@ -76,6 +78,12 @@ public abstract class FunctionGenerationStrategy {
             doGenerateBody(codegen, signature);
         }
 
+        @Override
+        public boolean skipNotNullAssertionsForParameters() {
+            // Assume the strategy injects non-null checks for parameters by default
+            return false;
+        }
+
         public abstract void doGenerateBody(@NotNull ExpressionCodegen codegen, @NotNull JvmMethodSignature signature);
     }
 }

compiler/backend/src/org/jetbrains/kotlin/codegen/ImplementationBodyCodegen.java

@@ -671,6 +671,11 @@ public class ImplementationBodyCodegen extends ClassBodyCodegen {
                     }
                     iv.areturn(componentType);
                 }
+
+                @Override
+                public boolean skipNotNullAssertionsForParameters() {
+                    return false;
+                }
             });
         }
 
@@ -719,6 +724,11 @@ public class ImplementationBodyCodegen extends ClassBodyCodegen {
                     iv.areturn(thisDescriptorType);
                 }
 
+                @Override
+                public boolean skipNotNullAssertionsForParameters() {
+                    return false;
+                }
+
                 private void pushCapturedFieldsOnStack(InstructionAdapter iv, MutableClosure closure) {
                     ClassDescriptor captureThis = closure.getCaptureThis();
                     if (captureThis != null) {

compiler/backend/src/org/jetbrains/kotlin/codegen/JvmStaticInCompanionObjectGenerator.kt

@@ -44,6 +44,8 @@ class JvmStaticInCompanionObjectGenerator(
                 Synthetic(originElement, staticFunctionDescriptor),
                 staticFunctionDescriptor,
                 object : FunctionGenerationStrategy.CodegenBased(state) {
+                    override fun skipNotNullAssertionsForParameters(): Boolean = true
+
                     override fun doGenerateBody(codegen: ExpressionCodegen, signature: JvmMethodSignature) {
                         val iv = codegen.v
                         val classDescriptor = descriptor.containingDeclaration as ClassDescriptor

compiler/backend/src/org/jetbrains/kotlin/codegen/MemberCodegen.java

@@ -719,6 +719,11 @@ public abstract class MemberCodegen<T extends KtPureElement/* TODO: & KtDeclarat
             functionCodegen.generateMethod(
                     Synthetic(null, original), accessor,
                     new FunctionGenerationStrategy.CodegenBased(state) {
+                        @Override
+                        public boolean skipNotNullAssertionsForParameters() {
+                            return true;
+                        }
+
                         @Override
                         public void doGenerateBody(@NotNull ExpressionCodegen codegen, @NotNull JvmMethodSignature signature) {
                             markLineNumberForElement(element.getPsiOrParent(), codegen.v);
@@ -779,6 +784,11 @@ public abstract class MemberCodegen<T extends KtPureElement/* TODO: & KtDeclarat
 
                     iv.areturn(signature.getReturnType());
                 }
+
+                @Override
+                public boolean skipNotNullAssertionsForParameters() {
+                    return true;
+                }
             }
 
             if (accessor.isWithSyntheticGetterAccessor()) {

compiler/backend/src/org/jetbrains/kotlin/codegen/MultifileClassCodegen.kt

@@ -312,6 +312,10 @@ class MultifileClassCodegenImpl(
     }
 
     object DelegateToCompiledMemberGenerationStrategy : FunctionGenerationStrategy() {
+        override fun skipNotNullAssertionsForParameters(): kotlin.Boolean {
+            throw IllegalStateException("shouldn't be called")
+        }
+
         override fun generateBody(mv: MethodVisitor, frameMap: FrameMap, signature: JvmMethodSignature, context: MethodContext, parentCodegen: MemberCodegen<*>) {
             throw IllegalStateException("shouldn't be called")
         }

compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/CoroutineCodegen.kt

@@ -531,6 +531,10 @@ class CoroutineCodegenForNamedFunction private constructor(
 private const val COROUTINE_LAMBDA_PARAMETER_PREFIX = "p$"
 
 private object FailingFunctionGenerationStrategy : FunctionGenerationStrategy() {
+    override fun skipNotNullAssertionsForParameters(): kotlin.Boolean {
+        error("This functions must not be called")
+    }
+
     override fun generateBody(
             mv: MethodVisitor,
             frameMap: FrameMap,