[Wasm] Do not erase interfaces down to Any type in Wasm signature.

This enables overloading virtual methods with different interface types

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/ir2wasm/BodyGenerator.kt

@@ -255,7 +255,7 @@ class BodyGenerator(val context: WasmFunctionCodegenContext) : IrElementVisitorV
         // Processing it separately
         if (call.symbol == wasmSymbols.boxIntrinsic) {
             val toType = call.getTypeArgument(0)!!
-            val klass = toType.erasedUpperBound!!
+            val klass = toType.getRuntimeClass!!
             val structTypeName = context.referenceGcType(klass.symbol)
             val klassId = context.referenceClassId(klass.symbol)
 
@@ -332,7 +332,7 @@ class BodyGenerator(val context: WasmFunctionCodegenContext) : IrElementVisitorV
     }
 
     private fun generateTypeRTT(type: IrType) {
-        val rtClass = type.erasedUpperBound?.symbol ?: context.backendContext.irBuiltIns.anyClass
+        val rtClass = type.getRuntimeClass?.symbol ?: context.backendContext.irBuiltIns.anyClass
         body.buildGetGlobal(context.referenceClassRTT(rtClass))
     }
 

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/ir2wasm/TypeTransformer.kt

@@ -47,7 +47,7 @@ class WasmTypeTransformer(
         }
 
     fun IrType.toWasmGcRefType(): WasmType =
-        WasmRefNullType(WasmHeapType.Type(context.referenceGcType(erasedUpperBound?.symbol ?: builtIns.anyClass)))
+        WasmRefNullType(WasmHeapType.Type(context.referenceGcType(getRuntimeClass?.symbol ?: builtIns.anyClass)))
 
     fun IrType.toBoxedInlineClassType(): WasmType =
         toWasmGcRefType()
@@ -111,7 +111,7 @@ class WasmTypeTransformer(
 
 
 // Return null if upper bound is Any
-val IrTypeParameter.erasedUpperBound: IrClass?
+private val IrTypeParameter.erasedUpperBound: IrClass?
     get() {
         // Pick the (necessarily unique) non-interface upper bound if it exists
         for (type in superTypes) {
@@ -126,7 +126,10 @@ val IrType.erasedUpperBound: IrClass?
         is IrClassSymbol -> classifier.owner
         is IrTypeParameterSymbol -> classifier.owner.erasedUpperBound
         else -> throw IllegalStateException()
-    }.let {
+    }
+
+val IrType.getRuntimeClass: IrClass?
+    get() = erasedUpperBound.let {
         if (it?.isInterface == true) null
         else it
     }

compiler/ir/backend.wasm/src/org/jetbrains/kotlin/backend/wasm/lower/WasmTypeOperatorLowering.kt

@@ -13,9 +13,8 @@ import org.jetbrains.kotlin.backend.common.lower.at
 import org.jetbrains.kotlin.backend.common.lower.createIrBuilder
 import org.jetbrains.kotlin.backend.common.lower.irNot
 import org.jetbrains.kotlin.backend.wasm.WasmBackendContext
-import org.jetbrains.kotlin.backend.wasm.ir2wasm.erasedUpperBound
+import org.jetbrains.kotlin.backend.wasm.ir2wasm.getRuntimeClass
 import org.jetbrains.kotlin.ir.IrStatement
-import org.jetbrains.kotlin.ir.backend.js.utils.findUnitGetInstanceFunction
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.declarations.IrTypeParameter
@@ -100,7 +99,7 @@ class WasmBaseTypeOperatorTransformer(val context: WasmBackendContext) : IrEleme
         context.inlineClassesUtils.isTypeInlined(this)
 
     private val IrType.erasedType: IrType
-        get() = this.erasedUpperBound?.defaultType ?: builtIns.anyType
+        get() = this.getRuntimeClass?.defaultType ?: builtIns.anyType
 
     private fun generateTypeCheck(
         valueProvider: () -> IrExpression,