[FIR] Implement CONFLICTING_IMPORT diagnostic

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -951,6 +951,10 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val CANNOT_BE_IMPORTED by error<KtSimpleNameExpression>(PositioningStrategy.IMPORT_LAST_NAME) {
             parameter<Name>("name")
         }
+
+        val CONFLICTING_IMPORT by error<KtImportDirective>(PositioningStrategy.IMPORT_LAST_NAME) {
+            parameter<Name>("name")
+        }
     }
 }
 

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -48,6 +48,7 @@ import org.jetbrains.kotlin.psi.KtElement
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtFunction
 import org.jetbrains.kotlin.psi.KtIfExpression
+import org.jetbrains.kotlin.psi.KtImportDirective
 import org.jetbrains.kotlin.psi.KtModifierListOwner
 import org.jetbrains.kotlin.psi.KtNamedDeclaration
 import org.jetbrains.kotlin.psi.KtObjectDeclaration
@@ -522,5 +523,6 @@ object FirErrors {
     val CANNOT_ALL_UNDER_IMPORT_FROM_SINGLETON by error1<KtSimpleNameExpression, Name>(SourceElementPositioningStrategies.IMPORT_LAST_NAME)
     val PACKAGE_CANNOT_BE_IMPORTED by error0<KtSimpleNameExpression>(SourceElementPositioningStrategies.IMPORT_LAST_NAME)
     val CANNOT_BE_IMPORTED by error1<KtSimpleNameExpression, Name>(SourceElementPositioningStrategies.IMPORT_LAST_NAME)
+    val CONFLICTING_IMPORT by error1<KtImportDirective, Name>(SourceElementPositioningStrategies.IMPORT_LAST_NAME)
 
 }

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

@@ -6,11 +6,14 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.followAllAlias
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.resolve.symbolProvider
+import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
 import org.jetbrains.kotlin.name.ClassId
 
 object FirImportsChecker : FirFileChecker() {
@@ -24,14 +27,14 @@ object FirImportsChecker : FirFileChecker() {
                 checkCanBeImported(import, context, reporter)
             }
         }
+        checkConflictingImports(declaration.imports, context, reporter)
     }
 
     private fun checkAllUnderFromEnumEntry(import: FirImport, context: CheckerContext, reporter: DiagnosticReporter) {
         val fqName = import.importedFqName ?: return
         if (fqName.isRoot || fqName.parent().isRoot) return
         val classId = ClassId.topLevel(fqName.parent())
-        val classSymbol = context.session.symbolProvider.getClassLikeSymbolByFqName(classId) ?: return
-        val classFir = classSymbol.fir as? FirRegularClass ?: return
+        val classFir = classId.resolveToClass(context) ?: return
         if (classFir.isEnumClass && classFir.collectEnumEntries().any { it.name == fqName.shortName() }) {
             reporter.reportOn(import.source, FirErrors.CANNOT_ALL_UNDER_IMPORT_FROM_SINGLETON, classFir.name, context)
         }
@@ -42,12 +45,12 @@ object FirImportsChecker : FirFileChecker() {
         val importedName = importedFqName.shortName()
         //empty name come from LT in some erroneous cases
         if (importedName.isSpecial || importedName.identifier.isEmpty()) return
+
         val classId = (import as? FirResolvedImport)?.resolvedClassId
         if (classId != null) {
-            val classSymbol = context.session.symbolProvider.getClassLikeSymbolByFqName(classId) ?: return
-            val classFir = classSymbol.fir as? FirRegularClass ?: return
+            val classFir = classId.resolveToClass(context) ?: return
             if (classFir.classKind.isSingleton) return
-            
+
             val illegalImport = classFir.declarations.any {
                 it is FirSimpleFunction && !it.isStatic && it.name == importedName ||
                         it is FirProperty && it.name == importedName
@@ -65,4 +68,48 @@ object FirImportsChecker : FirFileChecker() {
             }
         }
     }
+
+    private fun checkConflictingImports(imports: List<FirImport>, context: CheckerContext, reporter: DiagnosticReporter) {
+        val interestingImports = imports
+            .filterIsInstance<FirResolvedImport>()
+            .filter { import ->
+                !import.isAllUnder
+                        && import.importedName?.identifierOrNullIfSpecial?.isNotEmpty() == true
+                        && import.resolvesToClass(context)
+            }
+        interestingImports
+            .groupBy { it.aliasName ?: it.importedName!! }
+            .values
+            .filter { it.size > 1 }
+            .forEach { conflicts ->
+                conflicts.forEach {
+                    reporter.reportOn(it.source, FirErrors.CONFLICTING_IMPORT, it.importedName!!, context)
+                }
+            }
+    }
+
+    private fun FirResolvedImport.resolvesToClass(context: CheckerContext): Boolean {
+        if (resolvedClassId != null) {
+            if (isAllUnder) return true
+            val parentClass = resolvedClassId!!
+            val relativeClassName = this.relativeClassName ?: return false
+            val importedName = this.importedName ?: return false
+            val innerClassId = ClassId(parentClass.packageFqName, relativeClassName.child(importedName), false)
+            return innerClassId.resolveToClass(context) != null
+        } else {
+            val importedFqName = importedFqName ?: return false
+            if (importedFqName.isRoot) return false
+            val importedClassId = ClassId.topLevel(importedFqName)
+            return importedClassId.resolveToClass(context) != null
+        }
+    }
+
+    private fun ClassId.resolveToClass(context: CheckerContext): FirRegularClass? {
+        val classSymbol = context.session.symbolProvider.getClassLikeSymbolByFqName(this) ?: return null
+        return when (classSymbol) {
+            is FirRegularClassSymbol -> classSymbol.fir
+            is FirTypeAliasSymbol -> classSymbol.fir.followAllAlias(context.session) as? FirRegularClass
+            else -> null
+        }
+    }
 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt

@@ -70,6 +70,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.COMPONENT_FUNCTIO
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.COMPONENT_FUNCTION_ON_NULLABLE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.COMPONENT_FUNCTION_RETURN_TYPE_MISMATCH
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CONDITION_TYPE_MISMATCH
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CONFLICTING_IMPORT
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CONFLICTING_OVERLOADS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CONFLICTING_PROJECTION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CONFLICTING_PROJECTION_IN_TYPEALIAS_EXPANSION
@@ -1174,6 +1175,11 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
                 "Cannot import ''{0}'', functions and properties can be imported only from packages or objects",
                 TO_STRING
             )
+            map.put(
+                CONFLICTING_IMPORT,
+                "Conflicting import, imported name ''{0}'' is ambiguous",
+                TO_STRING
+            )
 
             // Extended checkers group
             map.put(REDUNDANT_VISIBILITY_MODIFIER, "Redundant visibility modifier")

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt

@@ -6,10 +6,7 @@
 package org.jetbrains.kotlin.diagnostics
 
 import com.intellij.openapi.util.TextRange
-import com.intellij.psi.PsiComment
-import com.intellij.psi.PsiElement
-import com.intellij.psi.PsiNameIdentifierOwner
-import com.intellij.psi.PsiWhiteSpace
+import com.intellij.psi.*
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import com.intellij.psi.tree.TokenSet
 import org.jetbrains.kotlin.KtNodeTypes
@@ -891,6 +888,12 @@ object PositioningStrategies {
     }
 
     val IMPORT_LAST_NAME: PositioningStrategy<PsiElement> = object : PositioningStrategy<PsiElement>() {
+
+        override fun isValid(element: PsiElement): Boolean {
+            if (element is PsiErrorElement) return false
+            return !element.children.any { !isValid(it) }
+        }
+
         override fun mark(element: PsiElement): List<TextRange> {
             if (element is KtImportDirective) {
                 val importedReference = element.importedReference

compiler/testData/diagnostics/tests/imports/ClassImportsConflicting.fir.kt

@@ -1,15 +0,0 @@
-//FILE:a.kt
-package a
-
-import b.O
-import c.O
-
-//FILE:b.kt
-package b
-
-object O {}
-
-//FILE:c.kt
-package c
-
-object O {}

compiler/testData/diagnostics/tests/imports/ClassImportsConflicting.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 //FILE:a.kt
 package a
 

compiler/testData/diagnostics/tests/imports/ExplicitImportsAmbiguity.fir.kt

@@ -1,17 +0,0 @@
-// FILE: a.kt
-package a
-
-class X
-
-// FILE: b.kt
-package b
-
-class X
-
-// FILE: c.kt
-package c
-
-import a.X
-import b.X
-
-class Y : <!UNRESOLVED_REFERENCE!>X<!>

compiler/testData/diagnostics/tests/imports/ExplicitImportsAmbiguity.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // FILE: a.kt
 package a
 

compiler/testData/diagnostics/tests/imports/ImportClassClash.fir.kt

@@ -1,48 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-// FILE: 1.kt
-package a
-
-class someFun() {}
-fun someFun(i: Int) {}
-
-class someVal() {}
-val Int.someVal: Int get() = 3
-
-class A
-
-class B
-
-// FILE: 2.kt
-package b
-
-class someFun
-class someVal
-class someAll
-
-fun A() {}
-
-class B
-
-
-// FILE: 3.kt
-import a.someFun
-import b.someFun
-
-import a.someVal
-import b.someVal
-
-import a.A
-import b.A
-
-// FILE: 4.kt
-import b.*
-import a.B
-
-// FILE: 5.kt
-package b
-
-import a.B
-
-// FILE: 6.kt
-import a.B
-import b.B

compiler/testData/diagnostics/tests/imports/ImportClassClash.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // FILE: 1.kt
 package a

compiler/testData/diagnostics/tests/imports/NestedClassClash.fir.kt

@@ -1,31 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-// FILE: a.kt
-package a
-
-class A {
-    class B
-}
-
-// FILE: b.kt
-package a
-
-class D {
-    class B
-}
-
-// FILE: c.kt
-import a.A.B
-import a.D.B
-
-fun test(b: <!UNRESOLVED_REFERENCE!>B<!>) {
-    <!UNRESOLVED_REFERENCE!>B<!>()
-}
-
-// FILE: d.kt
-import a.A.*
-import a.D.*
-
-// todo ambiguvity here
-fun test2(b: <!UNRESOLVED_REFERENCE!>B<!>) {
-    <!UNRESOLVED_REFERENCE!>B<!>()
-}

compiler/testData/diagnostics/tests/imports/NestedClassClash.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // FILE: a.kt
 package a

compiler/testData/diagnostics/testsWithStdLib/annotations/throws.fir.kt

@@ -1,164 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER
-// FILE: main1.kt
-package abc1
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main2.kt
-package abc2
-
-import kotlin.jvm.Throws
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main3.kt
-package abc3
-
-import kotlin.Throws
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main4.kt
-package abc4
-
-import kotlin.Throws
-import kotlin.jvm.Throws
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main5.kt
-package abc5
-
-import kotlin.jvm.*
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main6.kt
-package abc6
-
-import kotlin.*
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main7.kt
-package abc7
-
-import kotlin.*
-import kotlin.jvm.*
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main8.kt
-package abc8
-
-import kotlin.*
-import kotlin.jvm.Throws
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}
-
-// FILE: main9.kt
-package abc9
-
-import kotlin.jvm.*
-import kotlin.Throws
-
-@Throws(Exception::class)
-fun foo1() {}
-
-@kotlin.Throws(Exception::class)
-fun foo2() {}
-
-@kotlin.jvm.Throws(Exception::class)
-fun foo3() {}
-
-fun foo5(x: Throws) {}
-fun foo6(x: kotlin.Throws) {}
-fun foo7(x: kotlin.jvm.Throws) {}

compiler/testData/diagnostics/testsWithStdLib/annotations/throws.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // FILE: main1.kt
 package abc1

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -34,6 +34,7 @@ import org.jetbrains.kotlin.psi.KtElement
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtFunction
 import org.jetbrains.kotlin.psi.KtIfExpression
+import org.jetbrains.kotlin.psi.KtImportDirective
 import org.jetbrains.kotlin.psi.KtModifierListOwner
 import org.jetbrains.kotlin.psi.KtNamedDeclaration
 import org.jetbrains.kotlin.psi.KtObjectDeclaration
@@ -2593,6 +2594,13 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.CONFLICTING_IMPORT) { firDiagnostic ->
+        ConflictingImportImpl(
+            firDiagnostic.a,
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirJvmErrors.CONFLICTING_JVM_DECLARATIONS) { firDiagnostic ->
         ConflictingJvmDeclarationsImpl(
             firDiagnostic as FirPsiDiagnostic<*>,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.psi.KtElement
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtFunction
 import org.jetbrains.kotlin.psi.KtIfExpression
+import org.jetbrains.kotlin.psi.KtImportDirective
 import org.jetbrains.kotlin.psi.KtModifierListOwner
 import org.jetbrains.kotlin.psi.KtNamedDeclaration
 import org.jetbrains.kotlin.psi.KtObjectDeclaration
@@ -1819,6 +1820,11 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         abstract val name: Name
     }
 
+    abstract class ConflictingImport : KtFirDiagnostic<KtImportDirective>() {
+        override val diagnosticClass get() = ConflictingImport::class
+        abstract val name: Name
+    }
+
     abstract class ConflictingJvmDeclarations : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = ConflictingJvmDeclarations::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -42,6 +42,7 @@ import org.jetbrains.kotlin.psi.KtElement
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtFunction
 import org.jetbrains.kotlin.psi.KtIfExpression
+import org.jetbrains.kotlin.psi.KtImportDirective
 import org.jetbrains.kotlin.psi.KtModifierListOwner
 import org.jetbrains.kotlin.psi.KtNamedDeclaration
 import org.jetbrains.kotlin.psi.KtObjectDeclaration
@@ -2951,6 +2952,14 @@ internal class CannotBeImportedImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class ConflictingImportImpl(
+    override val name: Name,
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.ConflictingImport(), KtAbstractFirDiagnostic<KtImportDirective> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class ConflictingJvmDeclarationsImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,