[FIR] Implement early calculation of "not SAM" flag for classes

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirDeclarationStatus.kt

@@ -35,6 +35,7 @@ interface FirDeclarationStatus : FirElement {
     val isData: Boolean
     val isSuspend: Boolean
     val isStatic: Boolean
+    val isNotSAM: Boolean
 
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R = visitor.visitDeclarationStatus(this, data)
 }

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirResolvedDeclarationStatus.kt

@@ -34,6 +34,7 @@ interface FirResolvedDeclarationStatus : FirDeclarationStatus {
     override val isData: Boolean
     override val isSuspend: Boolean
     override val isStatic: Boolean
+    override val isNotSAM: Boolean
 
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R = visitor.visitResolvedDeclarationStatus(this, data)
 }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/Utils.kt

@@ -6,11 +6,17 @@
 package org.jetbrains.kotlin.fir
 
 import org.jetbrains.kotlin.analyzer.ModuleInfo
+import org.jetbrains.kotlin.descriptors.Modality
+import org.jetbrains.kotlin.fir.declarations.FirProperty
+import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
+import org.jetbrains.kotlin.fir.declarations.impl.FirDeclarationStatusImpl
+import org.jetbrains.kotlin.fir.declarations.impl.FirModifiableClass
+import org.jetbrains.kotlin.fir.declarations.modality
 import org.jetbrains.kotlin.fir.expressions.FirBlock
 import org.jetbrains.kotlin.fir.expressions.FirExpression
 import org.jetbrains.kotlin.fir.expressions.FirExpressionWithSmartcast
 import org.jetbrains.kotlin.fir.expressions.FirWhenSubjectExpression
-import org.jetbrains.kotlin.fir.visitors.FirTransformer
 
 fun ModuleInfo.dependenciesWithoutSelf(): Sequence<ModuleInfo> = dependencies().asSequence().filter { it != this }
 
@@ -30,4 +36,27 @@ tailrec fun FirElement.unwrapSmartcast(): FirElement = if (this is FirExpression
     originalExpression.unwrapSmartcast()
 } else {
     this
+}
+
+private val PUBLIC_METHOD_NAMES_IN_OBJECT = setOf("equals", "hashCode", "getClass", "wait", "notify", "notifyAll", "toString")
+
+fun FirModifiableClass<FirRegularClass>.calculateSAM() {
+    val status = symbol.fir.status as FirDeclarationStatusImpl
+    var counter = 0
+    for (declaration in declarations) {
+        if (declaration is FirProperty && declaration.modality == Modality.ABSTRACT) {
+            status.isNotSAM = true
+            return
+        }
+        if (declaration is FirSimpleFunction) {
+            if (declaration.modality != Modality.ABSTRACT || declaration.name.asString() in PUBLIC_METHOD_NAMES_IN_OBJECT) {
+                continue
+            }
+            counter++
+            if (counter > 1) {
+                status.isNotSAM = true
+                return
+            }
+        }
+    }
 }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/impl/FirDeclarationStatusImpl.kt

@@ -121,6 +121,12 @@ open class FirDeclarationStatusImpl(
             this[STATIC] = value
         }
 
+    override var isNotSAM: Boolean
+        get() = this[NOT_SAM]
+        set(value) {
+            this[NOT_SAM] = value
+        }
+
     private enum class Modifier(val mask: Int) {
         EXPECT(0x1),
         ACTUAL(0x2),
@@ -136,7 +142,8 @@ open class FirDeclarationStatusImpl(
         COMPANION(0x800),
         DATA(0x1000),
         SUSPEND(0x2000),
-        STATIC(0x4000)
+        STATIC(0x4000),
+        NOT_SAM(0x8000)
     }
 
     override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {}

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt

@@ -302,7 +302,8 @@ object NodeConfigurator : AbstractFieldConfigurator() {
             +modality
             generateBooleanFields(
                 "expect", "actual", "override", "operator", "infix", "inline", "tailRec",
-                "external", "const", "lateInit", "inner", "companion", "data", "suspend", "static"
+                "external", "const", "lateInit", "inner", "companion", "data", "suspend",
+                "static", "notSAM"
             )
         }