diff --git a/compiler/testData/builtin-classes.txt b/compiler/testData/builtin-classes.txt
index 5611beca4ab..4c5416311ac 100644
--- a/compiler/testData/builtin-classes.txt
+++ b/compiler/testData/builtin-classes.txt
@@ -23,11 +23,11 @@ public final class Array</*0*/ reified T> : kotlin.Cloneable {
 
 public final class Boolean : kotlin.Comparable<kotlin.Boolean> {
     /*primary*/ private constructor Boolean()
-    public final fun and(/*0*/ other: kotlin.Boolean): kotlin.Boolean
+    public final infix fun and(/*0*/ other: kotlin.Boolean): kotlin.Boolean
     public open override /*1*/ fun compareTo(/*0*/ other: kotlin.Boolean): kotlin.Int
     public final operator fun not(): kotlin.Boolean
-    public final fun or(/*0*/ other: kotlin.Boolean): kotlin.Boolean
-    public final fun xor(/*0*/ other: kotlin.Boolean): kotlin.Boolean
+    public final infix fun or(/*0*/ other: kotlin.Boolean): kotlin.Boolean
+    public final infix fun xor(/*0*/ other: kotlin.Boolean): kotlin.Boolean
 }
 
 public final class BooleanArray : kotlin.Cloneable {
@@ -594,7 +594,7 @@ public interface Function</*0*/ out R> {
 
 public final class Int : kotlin.Number, kotlin.Comparable<kotlin.Int> {
     /*primary*/ private constructor Int()
-    public final fun and(/*0*/ other: kotlin.Int): kotlin.Int
+    public final infix fun and(/*0*/ other: kotlin.Int): kotlin.Int
     public final operator fun compareTo(/*0*/ other: kotlin.Byte): kotlin.Int
     public final operator fun compareTo(/*0*/ other: kotlin.Double): kotlin.Int
     public final operator fun compareTo(/*0*/ other: kotlin.Float): kotlin.Int
@@ -623,7 +623,7 @@ public final class Int : kotlin.Number, kotlin.Comparable<kotlin.Int> {
     public final operator fun mod(/*0*/ other: kotlin.Int): kotlin.Int
     public final operator fun mod(/*0*/ other: kotlin.Long): kotlin.Long
     public final operator fun mod(/*0*/ other: kotlin.Short): kotlin.Int
-    public final fun or(/*0*/ other: kotlin.Int): kotlin.Int
+    public final infix fun or(/*0*/ other: kotlin.Int): kotlin.Int
     public final operator fun plus(): kotlin.Int
     public final operator fun plus(/*0*/ other: kotlin.Byte): kotlin.Int
     public final operator fun plus(/*0*/ other: kotlin.Double): kotlin.Double
@@ -637,8 +637,8 @@ public final class Int : kotlin.Number, kotlin.Comparable<kotlin.Int> {
     public final operator fun rangeTo(/*0*/ other: kotlin.Int): kotlin.IntRange
     public final operator fun rangeTo(/*0*/ other: kotlin.Long): kotlin.LongRange
     public final operator fun rangeTo(/*0*/ other: kotlin.Short): kotlin.IntRange
-    public final fun shl(/*0*/ bits: kotlin.Int): kotlin.Int
-    public final fun shr(/*0*/ bits: kotlin.Int): kotlin.Int
+    public final infix fun shl(/*0*/ bits: kotlin.Int): kotlin.Int
+    public final infix fun shr(/*0*/ bits: kotlin.Int): kotlin.Int
     public final operator fun times(/*0*/ other: kotlin.Byte): kotlin.Int
     public final operator fun times(/*0*/ other: kotlin.Double): kotlin.Double
     public final operator fun times(/*0*/ other: kotlin.Float): kotlin.Float
@@ -652,8 +652,8 @@ public final class Int : kotlin.Number, kotlin.Comparable<kotlin.Int> {
     public open override /*1*/ fun toInt(): kotlin.Int
     public open override /*1*/ fun toLong(): kotlin.Long
     public open override /*1*/ fun toShort(): kotlin.Short
-    public final fun ushr(/*0*/ bits: kotlin.Int): kotlin.Int
-    public final fun xor(/*0*/ other: kotlin.Int): kotlin.Int
+    public final infix fun ushr(/*0*/ bits: kotlin.Int): kotlin.Int
+    public final infix fun xor(/*0*/ other: kotlin.Int): kotlin.Int
 
     public companion object Companion : kotlin.IntegerConstants<kotlin.Int> {
         /*primary*/ private constructor Companion()
@@ -770,7 +770,7 @@ public interface ListIterator</*0*/ out T> : kotlin.Iterator<T> {
 
 public final class Long : kotlin.Number, kotlin.Comparable<kotlin.Long> {
     /*primary*/ private constructor Long()
-    public final fun and(/*0*/ other: kotlin.Long): kotlin.Long
+    public final infix fun and(/*0*/ other: kotlin.Long): kotlin.Long
     public final operator fun compareTo(/*0*/ other: kotlin.Byte): kotlin.Int
     public final operator fun compareTo(/*0*/ other: kotlin.Double): kotlin.Int
     public final operator fun compareTo(/*0*/ other: kotlin.Float): kotlin.Int
@@ -799,7 +799,7 @@ public final class Long : kotlin.Number, kotlin.Comparable<kotlin.Long> {
     public final operator fun mod(/*0*/ other: kotlin.Int): kotlin.Long
     public final operator fun mod(/*0*/ other: kotlin.Long): kotlin.Long
     public final operator fun mod(/*0*/ other: kotlin.Short): kotlin.Long
-    public final fun or(/*0*/ other: kotlin.Long): kotlin.Long
+    public final infix fun or(/*0*/ other: kotlin.Long): kotlin.Long
     public final operator fun plus(): kotlin.Long
     public final operator fun plus(/*0*/ other: kotlin.Byte): kotlin.Long
     public final operator fun plus(/*0*/ other: kotlin.Double): kotlin.Double
@@ -813,8 +813,8 @@ public final class Long : kotlin.Number, kotlin.Comparable<kotlin.Long> {
     public final operator fun rangeTo(/*0*/ other: kotlin.Int): kotlin.LongRange
     public final operator fun rangeTo(/*0*/ other: kotlin.Long): kotlin.LongRange
     public final operator fun rangeTo(/*0*/ other: kotlin.Short): kotlin.LongRange
-    public final fun shl(/*0*/ bits: kotlin.Int): kotlin.Long
-    public final fun shr(/*0*/ bits: kotlin.Int): kotlin.Long
+    public final infix fun shl(/*0*/ bits: kotlin.Int): kotlin.Long
+    public final infix fun shr(/*0*/ bits: kotlin.Int): kotlin.Long
     public final operator fun times(/*0*/ other: kotlin.Byte): kotlin.Long
     public final operator fun times(/*0*/ other: kotlin.Double): kotlin.Double
     public final operator fun times(/*0*/ other: kotlin.Float): kotlin.Float
@@ -828,8 +828,8 @@ public final class Long : kotlin.Number, kotlin.Comparable<kotlin.Long> {
     public open override /*1*/ fun toInt(): kotlin.Int
     public open override /*1*/ fun toLong(): kotlin.Long
     public open override /*1*/ fun toShort(): kotlin.Short
-    public final fun ushr(/*0*/ bits: kotlin.Int): kotlin.Long
-    public final fun xor(/*0*/ other: kotlin.Long): kotlin.Long
+    public final infix fun ushr(/*0*/ bits: kotlin.Int): kotlin.Long
+    public final infix fun xor(/*0*/ other: kotlin.Long): kotlin.Long
 
     public companion object Companion : kotlin.IntegerConstants<kotlin.Long> {
         /*primary*/ private constructor Companion()
diff --git a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.kt b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.kt
index 84a5188e061..edf0b6bdee0 100644
--- a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.kt
+++ b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.kt
@@ -1,4 +1,4 @@
-tailrec fun Int.test(x : Int) : Int {
+tailrec infix fun Int.test(x : Int) : Int {
     if (this > 1) {
         return (this - 1) test x
     }
diff --git a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.txt b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.txt
index 74585d3c6eb..cce36af9c13 100644
--- a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.txt
+++ b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixCall.txt
@@ -1,4 +1,4 @@
 package
 
 public fun box(): kotlin.String
-@kotlin.tailrec() public fun kotlin.Int.test(/*0*/ x: kotlin.Int): kotlin.Int
+@kotlin.tailrec() public infix fun kotlin.Int.test(/*0*/ x: kotlin.Int): kotlin.Int
diff --git a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.kt b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.kt
index ba17e93ec7c..c533885426b 100644
--- a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.kt
+++ b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.kt
@@ -1,5 +1,5 @@
 // !DIAGNOSTICS: -UNUSED_PARAMETER
-tailrec fun Int.foo(x: Int) {
+tailrec infix fun Int.foo(x: Int) {
     if (x == 0) return
     val xx = x - 1
     return 1 foo xx
diff --git a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.txt b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.txt
index c2fc2c635d6..76d50de06e3 100644
--- a/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.txt
+++ b/compiler/testData/codegen/box/diagnostics/functions/tailRecursion/infixRecursiveCall.txt
@@ -1,4 +1,4 @@
 package
 
 public fun box(): kotlin.String
-@kotlin.tailrec() public fun kotlin.Int.foo(/*0*/ x: kotlin.Int): kotlin.Unit
+@kotlin.tailrec() public infix fun kotlin.Int.foo(/*0*/ x: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/AutoCreatedIt.kt b/compiler/testData/diagnostics/tests/AutoCreatedIt.kt
index 5e0f4ce9e08..b7f614eba6a 100644
--- a/compiler/testData/diagnostics/tests/AutoCreatedIt.kt
+++ b/compiler/testData/diagnostics/tests/AutoCreatedIt.kt
@@ -19,14 +19,14 @@ fun bar(<!UNUSED_PARAMETER!>f<!> :  (Int, Int) -> Int) {}
 fun bar1(<!UNUSED_PARAMETER!>f<!> :  (Int) -> Int) {}
 fun bar2(<!UNUSED_PARAMETER!>f<!> :  () -> Int) {}
 
-fun String.to(<!UNUSED_PARAMETER!>dest<!> : String) {
+infix fun String.to(<!UNUSED_PARAMETER!>dest<!> : String) {
 
 }
 
-fun String.on(<!UNUSED_PARAMETER!>predicate<!> :  (s : URI) -> Boolean) : URI {
+infix fun String.on(<!UNUSED_PARAMETER!>predicate<!> :  (s : URI) -> Boolean) : URI {
     return URI(this)
 }
 
 class URI(val body : Any) {
-    fun to(<!UNUSED_PARAMETER!>dest<!> : String) {}
+    infix fun to(<!UNUSED_PARAMETER!>dest<!> : String) {}
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/AutoCreatedIt.txt b/compiler/testData/diagnostics/tests/AutoCreatedIt.txt
index 3f8ba6777d5..76a467ded99 100644
--- a/compiler/testData/diagnostics/tests/AutoCreatedIt.txt
+++ b/compiler/testData/diagnostics/tests/AutoCreatedIt.txt
@@ -4,14 +4,14 @@ public fun bar(/*0*/ f: (kotlin.Int, kotlin.Int) -> kotlin.Int): kotlin.Unit
 public fun bar1(/*0*/ f: (kotlin.Int) -> kotlin.Int): kotlin.Unit
 public fun bar2(/*0*/ f: () -> kotlin.Int): kotlin.Unit
 public fun text(): kotlin.Unit
-public fun kotlin.String.on(/*0*/ predicate: (URI) -> kotlin.Boolean): URI
-public fun kotlin.String.to(/*0*/ dest: kotlin.String): kotlin.Unit
+public infix fun kotlin.String.on(/*0*/ predicate: (URI) -> kotlin.Boolean): URI
+public infix fun kotlin.String.to(/*0*/ dest: kotlin.String): kotlin.Unit
 
 public final class URI {
     public constructor URI(/*0*/ body: kotlin.Any)
     public final val body: kotlin.Any
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public final fun to(/*0*/ dest: kotlin.String): kotlin.Unit
+    public final infix fun to(/*0*/ dest: kotlin.String): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
diff --git a/compiler/testData/diagnostics/tests/BinaryCallsOnNullableValues.kt b/compiler/testData/diagnostics/tests/BinaryCallsOnNullableValues.kt
index 333670762e6..97a6a39012f 100644
--- a/compiler/testData/diagnostics/tests/BinaryCallsOnNullableValues.kt
+++ b/compiler/testData/diagnostics/tests/BinaryCallsOnNullableValues.kt
@@ -6,7 +6,7 @@ fun f(): Unit {
   var x: Int? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>1<!>
   x = null
   x <!UNSAFE_INFIX_CALL!>+<!> 1
-  x <!UNSAFE_INFIX_CALL!>plus<!> 1
+  x <!UNSAFE_INFIX_CALL, INFIX_MODIFIER_REQUIRED!>plus<!> 1
   x <!UNSAFE_INFIX_CALL!><<!> 1
   x <!UNSAFE_INFIX_CALL!>+=<!> 1
 
diff --git a/compiler/testData/diagnostics/tests/Infix.kt b/compiler/testData/diagnostics/tests/Infix.kt
index 93e185bb85d..c519a9127a5 100644
--- a/compiler/testData/diagnostics/tests/Infix.kt
+++ b/compiler/testData/diagnostics/tests/Infix.kt
@@ -8,6 +8,12 @@ class Example {
 infix fun Example.toExt(other: Example) = Pair(this, other)
 fun Example.toExtNonInfix(other: Example) = Pair(this, other)
 
+infix fun Example.toExtWithExtraParams(other: Example, blah: Int = 0) = Pair(this, other)
+fun Example.toExtNonInfixWithExtraParams(other: Example, blah: Int = 0) = Pair(this, other)
+
+infix fun Example.toExtDefaultValues(other: Example? = null, blah: Int = 0) = Pair(this, other)
+fun Example.toExtNonInfixDefaultValues(other: Example? = null, blah: Int = 0) = Pair(this, other)
+
 fun Example.withLambda(f: () -> Unit) = Pair(this, f)
 
 fun test() {
@@ -22,5 +28,11 @@ fun test() {
     a <!INFIX_MODIFIER_REQUIRED!>toExtNonInfix<!> b
     a.toExtNonInfix(b)
 
+    a toExtWithExtraParams b
+    a <!INFIX_MODIFIER_REQUIRED!>toExtNonInfixWithExtraParams<!> b
+
+    a toExtDefaultValues b
+    a <!INFIX_MODIFIER_REQUIRED!>toExtNonInfixDefaultValues<!> b
+
     a <!INFIX_MODIFIER_REQUIRED!>withLambda<!> { }
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/InfixModifierApplicability.kt b/compiler/testData/diagnostics/tests/InfixModifierApplicability.kt
index 6a9a5ff9919..f1fc4d6a720 100644
--- a/compiler/testData/diagnostics/tests/InfixModifierApplicability.kt
+++ b/compiler/testData/diagnostics/tests/InfixModifierApplicability.kt
@@ -5,6 +5,7 @@ infix fun <A, B> A.to(that: B): Pair<A, B> = Pair(this, that)
 
 infix fun String.o1(o: String) = o
 infix fun String.o2(o: String, o2: String? = null) = o
+infix fun String.o3(o: String = "", o2: String? = null) = o
 
 <!INAPPLICABLE_INFIX_MODIFIER!>infix<!> fun w1() {}
 <!INAPPLICABLE_INFIX_MODIFIER!>infix<!> fun w2(s: String) {}
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt
index 8e4be6efa34..8d07b8b532a 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.kt
@@ -1,5 +1,7 @@
 // !CHECK_TYPE
 
+infix fun Int.compareTo(<!UNUSED_PARAMETER!>o<!>: Int) = 0
+
 fun foo(a: Number): Int {
     val result = (a as Int) compareTo <!DEBUG_INFO_SMARTCAST!>a<!>
     checkSubtype<Int>(<!DEBUG_INFO_SMARTCAST!>a<!>)
@@ -10,4 +12,4 @@ fun bar(a: Number): Int {
     val result = 42 compareTo (a as Int)
     checkSubtype<Int>(<!DEBUG_INFO_SMARTCAST!>a<!>)
     return result
-}
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.txt b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.txt
index fdccaf6687a..12461e0b870 100644
--- a/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.txt
+++ b/compiler/testData/diagnostics/tests/dataFlowInfoTraversal/BinaryExpressionIdentifier.txt
@@ -2,3 +2,4 @@ package
 
 public fun bar(/*0*/ a: kotlin.Number): kotlin.Int
 public fun foo(/*0*/ a: kotlin.Number): kotlin.Int
+public infix fun kotlin.Int.compareTo(/*0*/ o: kotlin.Int): kotlin.Int
diff --git a/compiler/testData/diagnostics/tests/evaluate/numberBinaryOperationsInfixCall.kt b/compiler/testData/diagnostics/tests/evaluate/numberBinaryOperationsInfixCall.kt
index 77aedf5c7cc..983c609ff6f 100644
--- a/compiler/testData/diagnostics/tests/evaluate/numberBinaryOperationsInfixCall.kt
+++ b/compiler/testData/diagnostics/tests/evaluate/numberBinaryOperationsInfixCall.kt
@@ -4,23 +4,23 @@ fun fooByte(p: Byte) = p
 fun fooShort(p: Short) = p
 
 fun test() {
-    fooInt(1 plus 1)
-    fooByte(1 plus 1)
-    fooLong(1 plus 1)
-    fooShort(1 plus 1)
+    fooInt(1 <!INFIX_MODIFIER_REQUIRED!>plus<!> 1)
+    fooByte(1 <!INFIX_MODIFIER_REQUIRED!>plus<!> 1)
+    fooLong(1 <!INFIX_MODIFIER_REQUIRED!>plus<!> 1)
+    fooShort(1 <!INFIX_MODIFIER_REQUIRED!>plus<!> 1)
 
-    fooInt(1 times 1)
-    fooByte(1 times 1)
-    fooLong(1 times 1)
-    fooShort(1 times 1)
+    fooInt(1 <!INFIX_MODIFIER_REQUIRED!>times<!> 1)
+    fooByte(1 <!INFIX_MODIFIER_REQUIRED!>times<!> 1)
+    fooLong(1 <!INFIX_MODIFIER_REQUIRED!>times<!> 1)
+    fooShort(1 <!INFIX_MODIFIER_REQUIRED!>times<!> 1)
 
-    fooInt(1 div 1)
-    fooByte(1 div 1)
-    fooLong(1 div 1)
-    fooShort(1 div 1)
+    fooInt(1 <!INFIX_MODIFIER_REQUIRED!>div<!> 1)
+    fooByte(1 <!INFIX_MODIFIER_REQUIRED!>div<!> 1)
+    fooLong(1 <!INFIX_MODIFIER_REQUIRED!>div<!> 1)
+    fooShort(1 <!INFIX_MODIFIER_REQUIRED!>div<!> 1)
 
-    fooInt(1 mod 1)
-    fooByte(1 mod 1)
-    fooLong(1 mod 1)
-    fooShort(1 mod 1)
+    fooInt(1 <!INFIX_MODIFIER_REQUIRED!>mod<!> 1)
+    fooByte(1 <!INFIX_MODIFIER_REQUIRED!>mod<!> 1)
+    fooLong(1 <!INFIX_MODIFIER_REQUIRED!>mod<!> 1)
+    fooShort(1 <!INFIX_MODIFIER_REQUIRED!>mod<!> 1)
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt b/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt
index e1054b448c5..c11724ad947 100644
--- a/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt
+++ b/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt
@@ -16,7 +16,7 @@ fun <T: Any, E> T.foo(<!UNUSED_PARAMETER!>x<!> : E, y : A) : T   {
 
 class A
 
-operator fun A.plus(<!UNUSED_PARAMETER!>a<!> : Any) {
+infix operator fun A.plus(<!UNUSED_PARAMETER!>a<!> : Any) {
 
   1.foo()
   true.<!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>foo<!>(<!NO_VALUE_FOR_PARAMETER, NO_VALUE_FOR_PARAMETER!>)<!>
diff --git a/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.txt b/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.txt
index 81bc8b32159..e0710a321c7 100644
--- a/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.txt
+++ b/compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.txt
@@ -25,7 +25,7 @@ package outer {
     public fun kotlin.Int.foo(): kotlin.Int
     public operator fun </*0*/ T> T.minus(/*0*/ t: T): kotlin.Int
     public fun kotlin.Int?.optint(): kotlin.Unit
-    public operator fun outer.A.plus(/*0*/ a: kotlin.Any): kotlin.Unit
+    public operator infix fun outer.A.plus(/*0*/ a: kotlin.Any): kotlin.Unit
     public operator fun outer.A.plus(/*0*/ a: kotlin.Int): kotlin.Unit
 
     public final class A {
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/kt4529.kt b/compiler/testData/diagnostics/tests/functionLiterals/kt4529.kt
index 517f4e427b8..00cf35a4f33 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/kt4529.kt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/kt4529.kt
@@ -1,7 +1,7 @@
 //KT-4529 Lambdas are analyzed improperly in an infix call nested inside a println
 
 class G {
-    fun foo(bar: (Int) -> Int) = bar
+    infix fun foo(bar: (Int) -> Int) = bar
 }
 
 fun main(args: Array<String>) {
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/kt4529.txt b/compiler/testData/diagnostics/tests/functionLiterals/kt4529.txt
index 21ae4e3b210..279882f449d 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/kt4529.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/kt4529.txt
@@ -6,7 +6,7 @@ public fun use(/*0*/ a: kotlin.Any?): kotlin.Any?
 public final class G {
     public constructor G()
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public final fun foo(/*0*/ bar: (kotlin.Int) -> kotlin.Int): (kotlin.Int) -> kotlin.Int
+    public final infix fun foo(/*0*/ bar: (kotlin.Int) -> kotlin.Int): (kotlin.Int) -> kotlin.Int
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.kt b/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.kt
index 0475b116d4f..3292e3a15a7 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.kt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.kt
@@ -4,7 +4,7 @@ interface Foo
 fun (Foo.() -> Unit).invoke(b : Foo.() -> Unit)  {}
 
 object Z {
-    fun add(b : Foo.() -> Unit) : Z = Z
+    infix fun add(b : Foo.() -> Unit) : Z = Z
 }
 
 val t2 = Z add <!TYPE_MISMATCH!>{ } <!TOO_MANY_ARGUMENTS!>{ }<!><!>
diff --git a/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.txt b/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.txt
index 8f9a99c63c8..0e2cb190a69 100644
--- a/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.txt
+++ b/compiler/testData/diagnostics/tests/functionLiterals/kt6541_extensionForExtensionFunction.txt
@@ -11,7 +11,7 @@ public interface Foo {
 
 public object Z {
     private constructor Z()
-    public final fun add(/*0*/ b: Foo.() -> kotlin.Unit): Z
+    public final infix fun add(/*0*/ b: Foo.() -> kotlin.Unit): Z
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
diff --git a/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.kt b/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.kt
index 36a1fcdc553..1e3724fee47 100644
--- a/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.kt
+++ b/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.kt
@@ -13,5 +13,5 @@ fun test() {
 // from library
 class Pair<out A, out B>
 fun <K, V> mapOf(keyValuePair: Pair<K, V>): Map<K, V> = throw Exception()
-fun <A, B> A.to(that: B): Pair<A, B> = throw Exception()
+infix fun <A, B> A.to(that: B): Pair<A, B> = throw Exception()
 
diff --git a/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.txt b/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.txt
index 93eaf8dc80c..2b8ab1ff5d3 100644
--- a/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.txt
+++ b/compiler/testData/diagnostics/tests/inference/commonSystem/fixVariablesInRightOrder.txt
@@ -4,7 +4,7 @@ public fun </*0*/ T> bar(/*0*/ t: T, /*1*/ ext: GenericClass<T>.() -> kotlin.Uni
 public fun </*0*/ K, /*1*/ V> mapOf(/*0*/ keyValuePair: Pair<K, V>): kotlin.Map<K, V>
 public fun test(): kotlin.Unit
 public fun </*0*/ K, /*1*/ V> GenericClass<kotlin.Map<K, V>>.foo(): kotlin.Unit
-public fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
+public infix fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
 
 public final class GenericClass</*0*/ out T> {
     public constructor GenericClass</*0*/ out T>()
diff --git a/compiler/testData/diagnostics/tests/inference/mapFunction.kt b/compiler/testData/diagnostics/tests/inference/mapFunction.kt
index 002afc39a71..5717fb0770e 100644
--- a/compiler/testData/diagnostics/tests/inference/mapFunction.kt
+++ b/compiler/testData/diagnostics/tests/inference/mapFunction.kt
@@ -25,10 +25,10 @@ fun foo() {
 
 
 // ---------------------
-// copy from kotlin util
+// copy from kotlin util (but with `infix` modifier on `map`)
 
 fun <T> array(vararg t : T) : Array<T> = t as Array<T>
 
-fun <T, R> Array<T>.map(<!UNUSED_PARAMETER!>transform<!> : (T) -> R) : List<R> {<!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
+infix fun <T, R> Array<T>.map(<!UNUSED_PARAMETER!>transform<!> : (T) -> R) : List<R> {<!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
 
-fun <T, R> Iterable<T>.map(<!UNUSED_PARAMETER!>transform<!> : (T) -> R) : List<R> {<!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
\ No newline at end of file
+infix fun <T, R> Iterable<T>.map(<!UNUSED_PARAMETER!>transform<!> : (T) -> R) : List<R> {<!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/inference/mapFunction.txt b/compiler/testData/diagnostics/tests/inference/mapFunction.txt
index bcb41d68574..2ad8f81b7a8 100644
--- a/compiler/testData/diagnostics/tests/inference/mapFunction.txt
+++ b/compiler/testData/diagnostics/tests/inference/mapFunction.txt
@@ -3,6 +3,6 @@ package
 package a {
     public fun </*0*/ T> array(/*0*/ vararg t: T /*kotlin.Array<out T>*/): kotlin.Array<T>
     public fun foo(): kotlin.Unit
-    public fun </*0*/ T, /*1*/ R> kotlin.Array<T>.map(/*0*/ transform: (T) -> R): kotlin.List<R>
-    public fun </*0*/ T, /*1*/ R> kotlin.Iterable<T>.map(/*0*/ transform: (T) -> R): kotlin.List<R>
+    public infix fun </*0*/ T, /*1*/ R> kotlin.Array<T>.map(/*0*/ transform: (T) -> R): kotlin.List<R>
+    public infix fun </*0*/ T, /*1*/ R> kotlin.Iterable<T>.map(/*0*/ transform: (T) -> R): kotlin.List<R>
 }
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt
index c938327b3aa..596a86607ea 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.kt
@@ -10,7 +10,7 @@ fun <T> id(t: T): T = t
 
 //binary expressions
 //identifier
-fun <T> Z.foo(a: A<T>): A<T> = a
+infix fun <T> Z.foo(a: A<T>): A<T> = a
 
 fun test(z: Z) {
     z <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>foo<!> <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>newA<!>()
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt
index 8665c7ff112..2949b66ef14 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/binaryExpressions.txt
@@ -13,7 +13,7 @@ package h {
     public fun use(/*0*/ vararg a: kotlin.Any? /*kotlin.Array<out kotlin.Any?>*/): kotlin.Array<out kotlin.Any?>
     public operator fun </*0*/ T> h.Z.compareTo(/*0*/ a: h.A<T>): kotlin.Int
     public fun h.Z.equals(/*0*/ any: kotlin.Any): kotlin.Int
-    public fun </*0*/ T> h.Z.foo(/*0*/ a: h.A<T>): h.A<T>
+    public infix fun </*0*/ T> h.Z.foo(/*0*/ a: h.A<T>): h.A<T>
     public operator fun </*0*/ T> h.Z.plus(/*0*/ a: h.A<T>): h.A<T>
 
     public interface A</*0*/ T> {
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.kt b/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.kt
index 0e643003412..df887b2f1c3 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.kt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.kt
@@ -2,7 +2,7 @@
 
 package aaa
 
-fun <T> T.foo(t: T) = t
+infix fun <T> T.foo(t: T) = t
 
 fun <T> id(t: T) = t
 
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.txt b/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.txt
index 4e374690ec7..0f3c6329118 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.txt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/inferenceForNestedBinaryCall.txt
@@ -3,5 +3,5 @@ package
 package aaa {
     public fun a(): kotlin.Unit
     public fun </*0*/ T> id(/*0*/ t: T): T
-    public fun </*0*/ T> T.foo(/*0*/ t: T): T
+    public infix fun </*0*/ T> T.foo(/*0*/ t: T): T
 }
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.kt b/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.kt
index 10c73e6f469..f0fe0f47d5f 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.kt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.kt
@@ -10,7 +10,7 @@ public fun <T> query(<!UNUSED_PARAMETER!>t<!>: T, <!UNUSED_PARAMETER!>args<!>: M
 fun test(pair: Pair<String, Int>) {
     val id = "Hello" // variable is marked as unused
 
-    println("Some" + query(0, mapOf(id  to 1)))
+    println("Some" + query(0, mapOf(id to 1)))
 
     println("Some" + query(0, mapOf(pair)))
 }
@@ -19,7 +19,7 @@ fun test(pair: Pair<String, Int>) {
 //from standard library
 fun <K, V> mapOf(vararg <!UNUSED_PARAMETER!>values<!>: Pair<K, V>): Map<K, V> { throw Exception() }
 
-fun <A,B> A.to(<!UNUSED_PARAMETER!>that<!>: B): Pair<A, B> { throw Exception() }
+infix fun <A,B> A.to(<!UNUSED_PARAMETER!>that<!>: B): Pair<A, B> { throw Exception() }
 
 fun println(<!UNUSED_PARAMETER!>message<!> : Any?) { throw Exception() }
 
diff --git a/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.txt b/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.txt
index 5db538c973d..610ee7fb392 100644
--- a/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.txt
+++ b/compiler/testData/diagnostics/tests/inference/nestedCalls/kt3395.txt
@@ -7,7 +7,7 @@ package b {
     public fun </*0*/ T> query(/*0*/ t: T, /*1*/ args: kotlin.Map<kotlin.String, kotlin.Any>): kotlin.List<T>
     public fun test(/*0*/ pair: b.Pair<kotlin.String, kotlin.Int>): kotlin.Unit
     public fun test(/*0*/ t: kotlin.String): kotlin.Unit
-    public fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): b.Pair<A, B>
+    public infix fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): b.Pair<A, B>
 
     public final class Pair</*0*/ out A, /*1*/ out B> {
         public constructor Pair</*0*/ out A, /*1*/ out B>()
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt1029.kt b/compiler/testData/diagnostics/tests/inference/regressions/kt1029.kt
index 62d6662f1d0..20da0c58420 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt1029.kt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt1029.kt
@@ -6,7 +6,7 @@ package i
 public fun<T> from(<!UNUSED_PARAMETER!>yielder<!>: ()->Iterable<T>) : Iterable<T> {
 <!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
 
-public fun<T> Iterable<T>.where(<!UNUSED_PARAMETER!>predicate<!> : (T)->Boolean) : ()->Iterable<T> {
+public infix fun<T> Iterable<T>.where(<!UNUSED_PARAMETER!>predicate<!> : (T)->Boolean) : ()->Iterable<T> {
 <!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
 
 fun a() {
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt1029.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt1029.txt
index 1e12dbb5ff1..89617f24f82 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt1029.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt1029.txt
@@ -3,5 +3,5 @@ package
 package i {
     public fun a(): kotlin.Unit
     public fun </*0*/ T> from(/*0*/ yielder: () -> kotlin.Iterable<T>): kotlin.Iterable<T>
-    public fun </*0*/ T> kotlin.Iterable<T>.where(/*0*/ predicate: (T) -> kotlin.Boolean): () -> kotlin.Iterable<T>
+    public infix fun </*0*/ T> kotlin.Iterable<T>.where(/*0*/ predicate: (T) -> kotlin.Boolean): () -> kotlin.Iterable<T>
 }
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt1031.kt b/compiler/testData/diagnostics/tests/inference/regressions/kt1031.kt
index 6240a70a77a..c9fdca53736 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt1031.kt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt1031.kt
@@ -5,7 +5,7 @@ package i
 
 import java.util.ArrayList
 
-public fun<TItem> Iterable<TItem>.where(<!UNUSED_PARAMETER!>predicate<!> : (TItem)->Boolean) : ()->Iterable<TItem> {
+public infix fun<TItem> Iterable<TItem>.where(<!UNUSED_PARAMETER!>predicate<!> : (TItem)->Boolean) : ()->Iterable<TItem> {
 <!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
 
 public fun<TItem, TResult> select(<!UNUSED_PARAMETER!>yielder<!>: ()->Iterable<TItem>, <!UNUSED_PARAMETER!>selector<!> : (TItem)->TResult) : ()->Iterable<TResult> {
diff --git a/compiler/testData/diagnostics/tests/inference/regressions/kt1031.txt b/compiler/testData/diagnostics/tests/inference/regressions/kt1031.txt
index 7c0b60efd6f..7a00188f81d 100644
--- a/compiler/testData/diagnostics/tests/inference/regressions/kt1031.txt
+++ b/compiler/testData/diagnostics/tests/inference/regressions/kt1031.txt
@@ -3,5 +3,5 @@ package
 package i {
     public fun a(): kotlin.Unit
     public fun </*0*/ TItem, /*1*/ TResult> select(/*0*/ yielder: () -> kotlin.Iterable<TItem>, /*1*/ selector: (TItem) -> TResult): () -> kotlin.Iterable<TResult>
-    public fun </*0*/ TItem> kotlin.Iterable<TItem>.where(/*0*/ predicate: (TItem) -> kotlin.Boolean): () -> kotlin.Iterable<TItem>
+    public infix fun </*0*/ TItem> kotlin.Iterable<TItem>.where(/*0*/ predicate: (TItem) -> kotlin.Boolean): () -> kotlin.Iterable<TItem>
 }
diff --git a/compiler/testData/diagnostics/tests/inline/capture.kt b/compiler/testData/diagnostics/tests/inline/capture.kt
index 55bd44aa557..5fd271b88ca 100644
--- a/compiler/testData/diagnostics/tests/inline/capture.kt
+++ b/compiler/testData/diagnostics/tests/inline/capture.kt
@@ -1,8 +1,8 @@
 // !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE -NOTHING_TO_INLINE -NON_LOCAL_RETURN_NOT_ALLOWED
 
-fun Function1<Int, Unit>.noInlineExt(p: Int) {}
+infix fun Function1<Int, Unit>.noInlineExt(p: Int) {}
 
-inline fun Function1<Int, Unit>.inlineExt2(p: Int) {
+inline infix fun Function1<Int, Unit>.inlineExt2(p: Int) {
     {
         <!USAGE_IS_NOT_INLINABLE!>noInlineExt<!>(11)
         <!USAGE_IS_NOT_INLINABLE!>this<!>.noInlineExt(11)
@@ -25,7 +25,7 @@ inline fun inlineFunWithInvoke(s: (p: Int) -> Unit) {
     {
         s(11)
         s.invoke(11)
-        s invoke 11
+        s <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
     }()
 }
 
@@ -33,7 +33,7 @@ inline fun inlineFunWithInvokeNonInline(noinline s: (p: Int) -> Unit) {
     {
         s(11)
         s.invoke(11)
-        s invoke 11
+        s <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
     }()
 }
 
diff --git a/compiler/testData/diagnostics/tests/inline/capture.txt b/compiler/testData/diagnostics/tests/inline/capture.txt
index 23742d23167..ba276daa0ab 100644
--- a/compiler/testData/diagnostics/tests/inline/capture.txt
+++ b/compiler/testData/diagnostics/tests/inline/capture.txt
@@ -5,5 +5,5 @@ package
 @kotlin.inline() public fun inlineFunWrongExtension(/*0*/ s: (kotlin.Int) -> kotlin.Unit): kotlin.Unit
 @kotlin.inline() public fun testExtension(/*0*/ s: (kotlin.Int) -> kotlin.Unit): kotlin.Unit
 @kotlin.inline() public fun ((kotlin.Int) -> kotlin.Unit).inlineExt(): kotlin.Unit
-@kotlin.inline() public fun ((kotlin.Int) -> kotlin.Unit).inlineExt2(/*0*/ p: kotlin.Int): kotlin.Unit
-public fun ((kotlin.Int) -> kotlin.Unit).noInlineExt(/*0*/ p: kotlin.Int): kotlin.Unit
+@kotlin.inline() public infix fun ((kotlin.Int) -> kotlin.Unit).inlineExt2(/*0*/ p: kotlin.Int): kotlin.Unit
+public infix fun ((kotlin.Int) -> kotlin.Unit).noInlineExt(/*0*/ p: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/inline/extensionOnFunction.kt b/compiler/testData/diagnostics/tests/inline/extensionOnFunction.kt
index 58f71163cae..3a6d3f50366 100644
--- a/compiler/testData/diagnostics/tests/inline/extensionOnFunction.kt
+++ b/compiler/testData/diagnostics/tests/inline/extensionOnFunction.kt
@@ -1,8 +1,8 @@
 // !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE -NOTHING_TO_INLINE
 
-fun Function1<Int, Unit>.noInlineExt(p: Int) {}
+infix fun Function1<Int, Unit>.noInlineExt(p: Int) {}
 
-inline fun Function1<Int, Unit>.inlineExt2(p: Int) {
+inline infix fun Function1<Int, Unit>.inlineExt2(p: Int) {
     <!USAGE_IS_NOT_INLINABLE!>noInlineExt<!>(11)
     <!USAGE_IS_NOT_INLINABLE!>this<!>.noInlineExt(11)
     <!USAGE_IS_NOT_INLINABLE!>this<!> noInlineExt 11
diff --git a/compiler/testData/diagnostics/tests/inline/extensionOnFunction.txt b/compiler/testData/diagnostics/tests/inline/extensionOnFunction.txt
index 9aebeeaa5f3..9c6b966fc01 100644
--- a/compiler/testData/diagnostics/tests/inline/extensionOnFunction.txt
+++ b/compiler/testData/diagnostics/tests/inline/extensionOnFunction.txt
@@ -4,5 +4,5 @@ package
 @kotlin.inline() public fun inlineFunWrongExtension(/*0*/ s: (kotlin.Int) -> kotlin.Unit): kotlin.Unit
 @kotlin.inline() public fun testExtension(/*0*/ s: (kotlin.Int) -> kotlin.Unit): kotlin.Unit
 @kotlin.inline() public fun ((kotlin.Int) -> kotlin.Unit).inlineExt(): kotlin.Unit
-@kotlin.inline() public fun ((kotlin.Int) -> kotlin.Unit).inlineExt2(/*0*/ p: kotlin.Int): kotlin.Unit
-public fun ((kotlin.Int) -> kotlin.Unit).noInlineExt(/*0*/ p: kotlin.Int): kotlin.Unit
+@kotlin.inline() public infix fun ((kotlin.Int) -> kotlin.Unit).inlineExt2(/*0*/ p: kotlin.Int): kotlin.Unit
+public infix fun ((kotlin.Int) -> kotlin.Unit).noInlineExt(/*0*/ p: kotlin.Int): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/inline/invoke.kt b/compiler/testData/diagnostics/tests/inline/invoke.kt
index 80db51f666c..d76a596549e 100644
--- a/compiler/testData/diagnostics/tests/inline/invoke.kt
+++ b/compiler/testData/diagnostics/tests/inline/invoke.kt
@@ -3,24 +3,24 @@
 inline fun inlineFunWithInvoke(s: (p: Int) -> Unit, ext: Int.(p: Int) -> Unit) {
     s(11)
     s.invoke(11)
-    s invoke 11
+    s <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
 
     11.ext(11)
-    11 ext 11
+    11 <!INFIX_MODIFIER_REQUIRED!>ext<!> 11
 }
 
 inline fun inlineFunWithInvokeNonInline(noinline s: (p: Int) -> Unit, ext: Int.(p: Int) -> Unit) {
     s(11)
     s.invoke(11)
-    s invoke 11
+    s <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
 
     11.ext(11)
-    11 ext 11
+    11 <!INFIX_MODIFIER_REQUIRED!>ext<!> 11
 }
 
 inline fun Function1<Int, Unit>.inlineExt() {
     invoke(11)
     this.invoke(11)
-    this invoke 11
+    this <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
     this(11)
-}
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.kt b/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.kt
index c209b5867d0..91a244fe12e 100644
--- a/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.kt
+++ b/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.kt
@@ -1,7 +1,7 @@
 // !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE -NOTHING_TO_INLINE
 
 class Z {
-    inline fun <R> inlineFun(crossinline p: () -> R) {
+    inline infix fun <R> inlineFun(crossinline p: () -> R) {
         p()
     }
 }
diff --git a/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.txt b/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.txt
index 54576420a72..4063f350520 100644
--- a/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.txt
+++ b/compiler/testData/diagnostics/tests/inline/nonLocalReturns/onlyLocalReturnLambdaBinaryExpr.txt
@@ -8,6 +8,6 @@ public final class Z {
     public constructor Z()
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    @kotlin.inline() public final fun </*0*/ R> inlineFun(/*0*/ @kotlin.crossinline() p: () -> R): kotlin.Unit
+    @kotlin.inline() public final infix fun </*0*/ R> inlineFun(/*0*/ @kotlin.crossinline() p: () -> R): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
diff --git a/compiler/testData/diagnostics/tests/inline/parenthesized.kt b/compiler/testData/diagnostics/tests/inline/parenthesized.kt
index eadaa818410..8eb98c0b647 100644
--- a/compiler/testData/diagnostics/tests/inline/parenthesized.kt
+++ b/compiler/testData/diagnostics/tests/inline/parenthesized.kt
@@ -3,13 +3,13 @@
 inline fun inlineFunWithInvoke(s: (p: Int) -> Unit) {
     (s)(11)
     (s).invoke(11)
-    (s) invoke 11
+    (s) <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
     (<!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>s<!>)
 }
 
 inline fun Function1<Int, Unit>.inlineExt() {
     (this).invoke(11)
-    (this) invoke 11
+    (this) <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
     (this)(11)
     (<!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>this<!>)
 }
@@ -17,7 +17,7 @@ inline fun Function1<Int, Unit>.inlineExt() {
 inline fun inlineFunWithInvoke2(s: (p: Int) -> Unit) {
     (((s)))(11)
     (((s))).invoke(11)
-    (((s))) invoke 11
+    (((s))) <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
     (((<!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>s<!>)))
 }
 
diff --git a/compiler/testData/diagnostics/tests/inline/sam.kt b/compiler/testData/diagnostics/tests/inline/sam.kt
index 845263fd63b..f20181901d1 100644
--- a/compiler/testData/diagnostics/tests/inline/sam.kt
+++ b/compiler/testData/diagnostics/tests/inline/sam.kt
@@ -17,10 +17,10 @@ inline fun inlineFunWithInvoke(s: (p: Int) -> Unit, ext: Int.(p: Int) -> Unit) {
     Test().test(){
         s(11)
         s.invoke(11)
-        s invoke 11
+        s <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
 
         11.ext(11)
-        11 ext 11
+        11 <!INFIX_MODIFIER_REQUIRED!>ext<!> 11
 
         <!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>s<!>
         <!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>ext<!>
@@ -32,10 +32,10 @@ inline fun inlineFunWithInvokeNonInline(noinline s: (p: Int) -> Unit, ext: Int.(
     Test().test(){
         s(11)
         s.invoke(11)
-        s invoke 11
+        s <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
 
         11.ext(11)
-        11 ext 11
+        11 <!INFIX_MODIFIER_REQUIRED!>ext<!> 11
 
         <!UNUSED_EXPRESSION!>s<!>
         <!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>ext<!>
@@ -48,7 +48,7 @@ inline fun Function1<Int, Unit>.inlineExt() {
     Test().test(){
         invoke(11)
         this.invoke(11)
-        this invoke 11
+        this <!INFIX_MODIFIER_REQUIRED!>invoke<!> 11
         this(11)
 
         <!USAGE_IS_NOT_INLINABLE, UNUSED_EXPRESSION!>this<!>
diff --git a/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.kt b/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.kt
index a124f892048..fec32c10412 100644
--- a/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.kt
+++ b/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.kt
@@ -1,16 +1,15 @@
 class A() {
-  operator fun plus(<!UNUSED_PARAMETER!>i<!> : Int) {}
+  operator infix fun plus(<!UNUSED_PARAMETER!>i<!> : Int) {}
   operator fun minus() {}
-  operator fun contains(<!UNUSED_PARAMETER!>a<!> : Any?) : Boolean = true
+  operator infix fun contains(<!UNUSED_PARAMETER!>a<!> : Any?) : Boolean = true
 }
 
-operator fun A.div(<!UNUSED_PARAMETER!>i<!> : Int) {}
-operator fun A?.times(<!UNUSED_PARAMETER!>i<!> : Int) {}
+operator infix fun A.div(<!UNUSED_PARAMETER!>i<!> : Int) {}
+operator infix fun A?.times(<!UNUSED_PARAMETER!>i<!> : Int) {}
 
 fun test(x : Int?, a : A?) {
     x<!UNSAFE_CALL!>.<!>plus(1)
     x?.plus(1)
-    x <!UNSAFE_INFIX_CALL!>plus<!> 1
     x <!UNSAFE_INFIX_CALL!>+<!> 1
     <!UNSAFE_CALL!>-<!>x
     x<!UNSAFE_CALL!>.<!>minus()
diff --git a/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.txt b/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.txt
index 3646a244fce..59fba32b8d3 100644
--- a/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.txt
+++ b/compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/InfixCallNullability.txt
@@ -1,15 +1,15 @@
 package
 
 public fun test(/*0*/ x: kotlin.Int?, /*1*/ a: A?): kotlin.Unit
-public operator fun A.div(/*0*/ i: kotlin.Int): kotlin.Unit
-public operator fun A?.times(/*0*/ i: kotlin.Int): kotlin.Unit
+public operator infix fun A.div(/*0*/ i: kotlin.Int): kotlin.Unit
+public operator infix fun A?.times(/*0*/ i: kotlin.Int): kotlin.Unit
 
 public final class A {
     public constructor A()
-    public final operator fun contains(/*0*/ a: kotlin.Any?): kotlin.Boolean
+    public final operator infix fun contains(/*0*/ a: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public final operator fun minus(): kotlin.Unit
-    public final operator fun plus(/*0*/ i: kotlin.Int): kotlin.Unit
+    public final operator infix fun plus(/*0*/ i: kotlin.Int): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
diff --git a/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.kt b/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.kt
index e8945dbb4c1..1c7670478e3 100644
--- a/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.kt
+++ b/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.kt
@@ -20,4 +20,4 @@ val x = B()["a", "v"]["a" to "b"] {} ["q" to "p"] // does not parses around {}
 
 //from library
 data class Pair<out A, out B> (val first: A, val second: B)
-fun <A,B> A.to(that: B) = Pair(this, that)
\ No newline at end of file
+infix fun <A,B> A.to(that: B) = Pair(this, that)
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.txt b/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.txt
index 8f0037df299..dce1dc05ab7 100644
--- a/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.txt
+++ b/compiler/testData/diagnostics/tests/operatorsOverloading/kt3450.txt
@@ -4,7 +4,7 @@ public val x: B
 public fun test(): kotlin.Unit
 public operator fun A.div(/*0*/ s: kotlin.String): A
 public operator fun kotlin.String.plus(): A
-public fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
+public infix fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
 
 public final class A {
     public constructor A()
diff --git a/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.kt b/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.kt
index 92006839405..26ad2b48d8b 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.kt
+++ b/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/arithmetic.kt
@@ -40,16 +40,15 @@ fun test() {
     platformN <!UNSAFE_INFIX_CALL!>+<!> 1
     platformJ + 1
 
-    1 plus platformNN
+    1 <!INFIX_MODIFIER_REQUIRED!>plus<!> platformNN
     1 <!NONE_APPLICABLE!>plus<!> platformN
-    1 plus platformJ
+    1 <!INFIX_MODIFIER_REQUIRED!>plus<!> platformJ
 
-    platformNN plus 1
-    platformN <!UNSAFE_INFIX_CALL!>plus<!> 1
-    platformJ plus 1
+    platformNN <!INFIX_MODIFIER_REQUIRED!>plus<!> 1
+    platformN <!UNSAFE_INFIX_CALL, INFIX_MODIFIER_REQUIRED!>plus<!> 1
+    platformJ <!INFIX_MODIFIER_REQUIRED!>plus<!> 1
 
     platformNN += 1
     platformN <!UNSAFE_INFIX_CALL!>+=<!> 1
     platformJ += 1
-}
-
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/regressions/kt385.109.441.kt b/compiler/testData/diagnostics/tests/regressions/kt385.109.441.kt
index 7045ffb6802..6a201f85e14 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt385.109.441.kt
+++ b/compiler/testData/diagnostics/tests/regressions/kt385.109.441.kt
@@ -4,9 +4,9 @@
 
 import java.util.*
 
-fun <T> Iterator<T>.foreach(operation: (element: T) -> Unit)  : Unit { while(hasNext()) operation(next()) }
+infix fun <T> Iterator<T>.foreach(operation: (element: T) -> Unit)  : Unit { while(hasNext()) operation(next()) }
 
-fun <T> Iterator<T>.foreach(operation: (index: Int, element: T) -> Unit) : Unit {
+infix fun <T> Iterator<T>.foreach(operation: (index: Int, element: T) -> Unit) : Unit {
     var k = 0
     while(hasNext())
         operation(k++, next())
diff --git a/compiler/testData/diagnostics/tests/regressions/kt385.109.441.txt b/compiler/testData/diagnostics/tests/regressions/kt385.109.441.txt
index b7c391432b4..5040571b965 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt385.109.441.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt385.109.441.txt
@@ -8,5 +8,5 @@ public fun println(/*0*/ message: kotlin.Long): kotlin.Unit
 @kotlin.inline() public fun </*0*/ T> run(/*0*/ body: () -> T): T
 public fun </*0*/ T> kotlin.Iterable<T>.foreach(/*0*/ operation: (T) -> kotlin.Unit): kotlin.Unit
 public fun </*0*/ T> kotlin.Iterable<T>.foreach(/*0*/ operation: (kotlin.Int, T) -> kotlin.Unit): kotlin.Unit
-public fun </*0*/ T> kotlin.Iterator<T>.foreach(/*0*/ operation: (T) -> kotlin.Unit): kotlin.Unit
-public fun </*0*/ T> kotlin.Iterator<T>.foreach(/*0*/ operation: (kotlin.Int, T) -> kotlin.Unit): kotlin.Unit
+public infix fun </*0*/ T> kotlin.Iterator<T>.foreach(/*0*/ operation: (T) -> kotlin.Unit): kotlin.Unit
+public infix fun </*0*/ T> kotlin.Iterator<T>.foreach(/*0*/ operation: (kotlin.Int, T) -> kotlin.Unit): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/regressions/kt442.kt b/compiler/testData/diagnostics/tests/regressions/kt442.kt
index c09cca93b3f..887d48959e0 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt442.kt
+++ b/compiler/testData/diagnostics/tests/regressions/kt442.kt
@@ -20,7 +20,7 @@ fun <T> generic_invoker(gen :  (String) -> T) : T {
     return gen("")
 }
 
-fun <T> T.with(f :  T.() -> Unit) {
+infix fun <T> T.with(f :  T.() -> Unit) {
     f()
 }
 
diff --git a/compiler/testData/diagnostics/tests/regressions/kt442.txt b/compiler/testData/diagnostics/tests/regressions/kt442.txt
index 4ec35e8db58..25db33cd53e 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt442.txt
+++ b/compiler/testData/diagnostics/tests/regressions/kt442.txt
@@ -7,4 +7,4 @@ public fun </*0*/ T> generic_invoker(/*0*/ gen: (kotlin.String) -> T): T
 public fun main(/*0*/ args: kotlin.Array<kotlin.String>): kotlin.Unit
 public fun testFunny(): kotlin.Unit
 public fun testFunny2(): kotlin.Unit
-public fun </*0*/ T> T.with(/*0*/ f: T.() -> kotlin.Unit): kotlin.Unit
+public infix fun </*0*/ T> T.with(/*0*/ f: T.() -> kotlin.Unit): kotlin.Unit
diff --git a/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.kt b/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.kt
index 09854d7cdf4..71aea3b88f6 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.kt
+++ b/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.kt
@@ -1,7 +1,7 @@
 package o
 
 class A {
-    fun foo(b: B) = b
+    infix fun foo(b: B) = b
 }
 
 class B {
diff --git a/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.txt b/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.txt
index 461d7351cd7..c6687274428 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/afterBinaryExpr.txt
@@ -6,7 +6,7 @@ package o {
     public final class A {
         public constructor A()
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-        public final fun foo(/*0*/ b: o.B): o.B
+        public final infix fun foo(/*0*/ b: o.B): o.B
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
     }
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.kt b/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.kt
index 99427844d31..87f51c9338a 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.kt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.kt
@@ -10,4 +10,4 @@ class Test {
 }
 
 class Pair<out A, out B>(val first: A, val second: B)
-fun <A, B> A.to(that: B) = Pair(this, that)
\ No newline at end of file
+infix fun <A, B> A.to(that: B) = Pair(this, that)
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt b/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt
index 611bb1bca39..53a25fbd224 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/inference/smartCastOnReceiver.txt
@@ -1,6 +1,6 @@
 package
 
-public fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
+public infix fun </*0*/ A, /*1*/ B> A.to(/*0*/ that: B): Pair<A, B>
 
 public interface A {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
diff --git a/compiler/testData/diagnostics/tests/smartCasts/kt3711.kt b/compiler/testData/diagnostics/tests/smartCasts/kt3711.kt
index 86ac84fc969..db7a36d3b9b 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/kt3711.kt
+++ b/compiler/testData/diagnostics/tests/smartCasts/kt3711.kt
@@ -1,6 +1,6 @@
 data class StringPair(val first: String, val second: String)
 
-fun String.to(second: String) = StringPair(this, second)
+infix fun String.to(second: String) = StringPair(this, second)
 
 fun f(a: String?) {
     if (a != null) {
diff --git a/compiler/testData/diagnostics/tests/smartCasts/kt3711.txt b/compiler/testData/diagnostics/tests/smartCasts/kt3711.txt
index 815dd3b0dfc..7076b7b05f9 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/kt3711.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/kt3711.txt
@@ -1,7 +1,7 @@
 package
 
 public fun f(/*0*/ a: kotlin.String?): kotlin.Unit
-public fun kotlin.String.to(/*0*/ second: kotlin.String): StringPair
+public infix fun kotlin.String.to(/*0*/ second: kotlin.String): StringPair
 
 @kotlin.data() public final class StringPair {
     public constructor StringPair(/*0*/ first: kotlin.String, /*1*/ second: kotlin.String)
diff --git a/compiler/testData/diagnostics/tests/smartCasts/kt3899.kt b/compiler/testData/diagnostics/tests/smartCasts/kt3899.kt
index be164c3d6d8..2a3b7c0ae86 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/kt3899.kt
+++ b/compiler/testData/diagnostics/tests/smartCasts/kt3899.kt
@@ -1,6 +1,6 @@
 data class StringPair(val first: String, val second: String)
 
-fun String.to(second: String) = StringPair(this, second)
+infix fun String.to(second: String) = StringPair(this, second)
 
 fun hashMapOf(<!UNUSED_PARAMETER!>pair<!>: StringPair): MutableMap<String, String> {
 <!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
diff --git a/compiler/testData/diagnostics/tests/smartCasts/kt3899.txt b/compiler/testData/diagnostics/tests/smartCasts/kt3899.txt
index 357936f623f..bfc97629990 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/kt3899.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/kt3899.txt
@@ -2,7 +2,7 @@ package
 
 public fun F(): kotlin.MutableMap<kotlin.String, kotlin.String>
 public fun hashMapOf(/*0*/ pair: StringPair): kotlin.MutableMap<kotlin.String, kotlin.String>
-public fun kotlin.String.to(/*0*/ second: kotlin.String): StringPair
+public infix fun kotlin.String.to(/*0*/ second: kotlin.String): StringPair
 
 @kotlin.data() public final class StringPair {
     public constructor StringPair(/*0*/ first: kotlin.String, /*1*/ second: kotlin.String)
diff --git a/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.kt b/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.kt
index d1e1267658f..770e1fcca6a 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.kt
+++ b/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.kt
@@ -2,7 +2,7 @@ public open class A() {
     public open val foo: Int? = 1
 }
 
-fun Int.bar(i: Int) = i
+infix fun Int.bar(i: Int) = i
 
 fun test() {
     val p = A()
diff --git a/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.txt b/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.txt
index 60b77df2d92..710c3753670 100644
--- a/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.txt
+++ b/compiler/testData/diagnostics/tests/smartCasts/publicVals/open.txt
@@ -1,7 +1,7 @@
 package
 
 public fun test(): kotlin.Unit
-public fun kotlin.Int.bar(/*0*/ i: kotlin.Int): kotlin.Int
+public infix fun kotlin.Int.bar(/*0*/ i: kotlin.Int): kotlin.Int
 
 public open class A {
     public constructor A()
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.java b/compiler/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.java
index 34c2169d33e..03f35a72029 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/BaseDiagnosticsTest.java
@@ -68,7 +68,7 @@ public abstract class BaseDiagnosticsTest extends
                                                           "\nfun <T> checkSubtype(t: T) = t" +
                                                           "\nclass Inv<T>" +
                                                           "\nfun <E> Inv<E>._() {}" +
-                                                          "\nfun <T> T.checkType(f: Inv<T>.() -> Unit) {}";
+                                                          "\ninfix fun <T> T.checkType(f: Inv<T>.() -> Unit) {}";
     public static final String CHECK_TYPE_IMPORT = "import " + CHECK_TYPE_PACKAGE + ".*";
 
     public static final String EXPLICIT_FLEXIBLE_TYPES_DIRECTIVE = "EXPLICIT_FLEXIBLE_TYPES";
diff --git a/idea/testData/checker/BinaryCallsOnNullableValues.kt b/idea/testData/checker/BinaryCallsOnNullableValues.kt
index 4342a082341..825c8769df2 100644
--- a/idea/testData/checker/BinaryCallsOnNullableValues.kt
+++ b/idea/testData/checker/BinaryCallsOnNullableValues.kt
@@ -6,7 +6,7 @@ fun f(): Unit {
   var x: Int? = <warning>1</warning>
   x = 1
   x + 1
-  x plus 1
+  x.plus(1)
   x < 1
   x += 1
 
diff --git a/idea/testData/checker/ExtensionFunctions.kt b/idea/testData/checker/ExtensionFunctions.kt
index c5113158532..b9f516263b0 100644
--- a/idea/testData/checker/ExtensionFunctions.kt
+++ b/idea/testData/checker/ExtensionFunctions.kt
@@ -13,7 +13,7 @@ fun <T: Any, E> T.foo(<warning>x</warning> : E, y : A) : T   {
 
 class A
 
-operator fun A.plus(<warning>a</warning> : Any) {
+infix operator fun A.plus(<warning>a</warning> : Any) {
 
   1.foo()
   true.<error>foo</error>(<error><error>)</error></error>
@@ -21,7 +21,7 @@ operator fun A.plus(<warning>a</warning> : Any) {
   <warning>1</warning>
 }
 
-operator fun A.plus(<warning>a</warning> : Int) {
+infix operator fun A.plus(<warning>a</warning> : Int) {
   <warning>1</warning>
 }
 
diff --git a/idea/testData/checker/rendering/TypeInferenceError.kt b/idea/testData/checker/rendering/TypeInferenceError.kt
index ac769f3af89..d82b2759194 100644
--- a/idea/testData/checker/rendering/TypeInferenceError.kt
+++ b/idea/testData/checker/rendering/TypeInferenceError.kt
@@ -7,5 +7,5 @@ fun foo() {
 
 //extract from library
 fun <K, V> hashMap(<warning>p</warning>: Pair<K, V>): MutableMap<K, V> {<error>}</error>
-fun <K, V> K.to(<warning>v</warning>: V): Pair<K, V> {<error>}</error>
+infix fun <K, V> K.to(<warning>v</warning>: V): Pair<K, V> {<error>}</error>
 class Pair<K, V> {}
\ No newline at end of file