FIR: Fix false positive INAPPLICABLE_INFIX_MODIFIER

compiler/fir/analysis-tests/testData/resolve/diagnostics/infixFunctions.kt

@@ -10,4 +10,15 @@ infix class A
 
 infix typealias B = A
 
-infix val x = 1
+infix val x = 1
+
+class C {
+    infix fun good(x: Int) {}
+    infix fun Int.goodAsWell(x: Int) {}
+
+    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun Int.foo(x: Int, y: Int) {}<!>
+
+    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun Int.bar() {}<!>
+
+    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun baz(x: Int, y: Int) {}<!>
+}

compiler/fir/analysis-tests/testData/resolve/diagnostics/infixFunctions.txt

@@ -16,3 +16,24 @@ FILE: infixFunctions.kt
     public final typealias B = R|A|
     public final val x: R|kotlin/Int| = Int(1)
         public get(): R|kotlin/Int|
+    public final class C : R|kotlin/Any| {
+        public constructor(): R|C| {
+            super<R|kotlin/Any|>()
+        }
+
+        public final infix fun good(x: R|kotlin/Int|): R|kotlin/Unit| {
+        }
+
+        public final infix fun R|kotlin/Int|.goodAsWell(x: R|kotlin/Int|): R|kotlin/Unit| {
+        }
+
+        public final infix fun R|kotlin/Int|.foo(x: R|kotlin/Int|, y: R|kotlin/Int|): R|kotlin/Unit| {
+        }
+
+        public final infix fun R|kotlin/Int|.bar(): R|kotlin/Unit| {
+        }
+
+        public final infix fun baz(x: R|kotlin/Int|, y: R|kotlin/Int|): R|kotlin/Unit| {
+        }
+
+    }

compiler/fir/analysis-tests/testData/resolve/fromBuilder/typeParameters.kt

@@ -1,7 +1,7 @@
 interface List<out T : Any> {
     operator fun get(index: Int): T
 
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun concat(other: List<T>): List<T><!>
+    infix fun concat(other: List<T>): List<T>
 }
 
 typealias StringList = List<out String>

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirInfixFunctionDeclarationChecker.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.fir.FirSourceElement
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
+import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.isInfix
@@ -16,7 +17,7 @@ import org.jetbrains.kotlin.fir.declarations.isInfix
 object FirInfixFunctionDeclarationChecker : FirDeclarationChecker<FirMemberDeclaration>() {
     override fun check(declaration: FirMemberDeclaration, context: CheckerContext, reporter: DiagnosticReporter) {
         if (declaration is FirSimpleFunction && declaration.isInfix) {
-            if (declaration.valueParameters.size != 1 || declaration.receiverTypeRef == null) {
+            if (declaration.valueParameters.size != 1 || !hasExtensionOrDispatchReceiver(declaration, context)) {
                 reporter.report(declaration.source)
             }
             return
@@ -26,7 +27,15 @@ object FirInfixFunctionDeclarationChecker : FirDeclarationChecker<FirMemberDecla
         }
     }
 
+    private fun hasExtensionOrDispatchReceiver(
+        function: FirSimpleFunction,
+        context: CheckerContext
+    ): Boolean {
+        if (function.receiverTypeRef != null) return true
+        return context.containingDeclarations.lastOrNull() is FirClass<*>
+    }
+
     private fun DiagnosticReporter.report(source: FirSourceElement?) {
         source?.let { report(FirErrors.INAPPLICABLE_INFIX_MODIFIER.on(it, "Inapplicable infix modifier")) }
     }
-}
+}

compiler/testData/diagnostics/tests/AutoCreatedIt.fir.kt

@@ -29,5 +29,5 @@ infix fun String.on(predicate :  (s : URI) -> Boolean) : URI {
 }
 
 class URI(val body : Any) {
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun to(dest : String) {}<!>
+    infix fun to(dest : String) {}
 }

compiler/testData/diagnostics/tests/Infix.fir.kt

@@ -1,7 +1,7 @@
 class Pair<out A, out B>(val first: A, val second: B)
 
 class Example {
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun to(other: Example) = Pair(this, other)<!>
+    infix fun to(other: Example) = Pair(this, other)
     fun toNonInfix(other: Example) = Pair(this, other)
 }
 
@@ -35,4 +35,4 @@ fun test() {
     a toExtNonInfixDefaultValues b
 
     a withLambda { }
-}
+}

compiler/testData/diagnostics/tests/InfixModifierApplicability.fir.kt

@@ -6,7 +6,7 @@ infix fun <A, B> A.to(that: B): Pair<A, B> = Pair(this, that)
 // OK
 infix fun String.ok1(o: String) {}
 class OkTest {
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun ok2(o: String) {}<!>
+    infix fun ok2(o: String) {}
     infix fun String.ok3(o: String) {}
 }
 
@@ -24,4 +24,4 @@ class Example {
     <!INAPPLICABLE_INFIX_MODIFIER!>infix fun e8(s: String, a: Int = 0) {}<!>
     <!INAPPLICABLE_INFIX_MODIFIER!>infix fun e9(s: String, a: Int) {}<!>
     <!INAPPLICABLE_INFIX_MODIFIER!>infix fun e10() {}<!>
-}
+}

compiler/testData/diagnostics/tests/OperatorChecks.fir.kt

@@ -59,9 +59,9 @@ interface Example {
     operator fun hasNext(): Boolean
     operator fun hasNext(n: Int): String
 
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun i1(n: Int)<!>
+    infix fun i1(n: Int)
     <!INAPPLICABLE_INFIX_MODIFIER!>infix fun i1(n: Int, n2: Int)<!>
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun i1(vararg n: Int)<!>
+    infix fun i1(vararg n: Int)
 }
 
 class OkDelegates {

compiler/testData/diagnostics/tests/functionLiterals/kt4529.fir.kt

@@ -1,19 +0,0 @@
-//KT-4529 Lambdas are analyzed improperly in an infix call nested inside a println
-
-class G {
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun foo(bar: (Int) -> Int) = bar<!>
-}
-
-fun main() {
-    use(
-            G().foo {it + 11} // no error
-    )
-    use(
-            G() foo {it + 11} // ERROR
-    )
-    use(
-            G() foo ({it + 1}) // 2 ERRORs
-    )
-}
-
-fun use(a: Any?) = a

compiler/testData/diagnostics/tests/functionLiterals/kt4529.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //KT-4529 Lambdas are analyzed improperly in an infix call nested inside a println
 
 class G {

compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.fir.kt

@@ -4,7 +4,7 @@ interface Foo
 fun (Foo.() -> Unit).invoke(b : Foo.() -> Unit)  {}
 
 object Z {
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun add(b : Foo.() -> Unit) : Z = Z<!>
+    infix fun add(b : Foo.() -> Unit) : Z = Z
 }
 
 val t2 = Z <!INAPPLICABLE_CANDIDATE!>add<!> { } { }

compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.fir.kt

@@ -1,9 +1,9 @@
 // !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE -NOTHING_TO_INLINE
 
 class Z {
-    <!INAPPLICABLE_INFIX_MODIFIER!>inline infix fun <R> inlineFun(crossinline p: () -> R) {
+    inline infix fun <R> inlineFun(crossinline p: () -> R) {
         p()
-    }<!>
+    }
 }
 
 fun <R> fun1(p: () -> R) {

compiler/testData/diagnostics/tests/modifiers/operatorInfix/MemberFunctions.fir.kt

@@ -1,10 +1,10 @@
 // !DIAGNOSTICS: -UNUSED_PARAMETER, -EXTENSION_SHADOWED_BY_MEMBER
 
 class Example {
-    <!INAPPLICABLE_INFIX_MODIFIER!>operator infix fun plus(other: Example) = 0<!>
+    operator infix fun plus(other: Example) = 0
     fun minus(other: Example) = 0
 
-    <!INAPPLICABLE_INFIX_MODIFIER!>operator infix fun times(other: Example) = 0<!>
+    operator infix fun times(other: Example) = 0
     fun div(other: Example) = 0
 }
 
@@ -42,4 +42,4 @@ fun a() {
 }
 
 fun consumeInt(i: Int) {}
-fun consumeString(s: String) {}
+fun consumeString(s: String) {}

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.fir.kt

@@ -1,8 +1,8 @@
 // !WITH_NEW_INFERENCE
 class A() {
-    <!INAPPLICABLE_INFIX_MODIFIER!>operator infix fun plus(i : Int) {}<!>
+    operator infix fun plus(i : Int) {}
     operator fun unaryMinus() {}
-    <!INAPPLICABLE_INFIX_MODIFIER!>operator infix fun contains(a : Any?) : Boolean = true<!>
+    operator infix fun contains(a : Any?) : Boolean = true
 }
 
 operator infix fun A.div(i : Int) {}

compiler/testData/diagnostics/tests/redeclarations/shadowedExtension/infixExtensionVsNonInfixMember.fir.kt

@@ -1,7 +1,7 @@
 interface IFoo {
     fun foo(i: Int): Int
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun bar(i: Int): Int<!>
+    infix fun bar(i: Int): Int
 }
 
 infix fun IFoo.foo(i: Int) = i
-infix fun IFoo.bar(i: Int) = i
+infix fun IFoo.bar(i: Int) = i

compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.fir.kt

@@ -1,7 +1,7 @@
 package o
 
 class A {
-    <!INAPPLICABLE_INFIX_MODIFIER!>infix fun foo(b: B) = b<!>
+    infix fun foo(b: B) = b
 }
 
 class B {
@@ -11,4 +11,4 @@ class B {
 fun test(a: A, b: B?) {
     a foo b!!
     b.bar()
-}
+}