K2 LL API: implement automatic diagnostic suppression

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostics/FileStructureElementDiagnosticsCollector.kt

@@ -27,6 +27,10 @@ internal class FileStructureElementDiagnosticsCollector private constructor(priv
             useExtendedCheckers,
         )
         collector.collectDiagnostics(firDeclaration, reporter)
-        return FileStructureElementDiagnosticList(reporter.diagnostics)
+        val source = firDeclaration.source
+        if (source != null) {
+            reporter.checkAndCommitReportsOn(source, null)
+        }
+        return FileStructureElementDiagnosticList(reporter.committedDiagnostics)
     }
 }

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostics/LLFirDiagnosticReporter.kt

@@ -6,11 +6,13 @@
 package org.jetbrains.kotlin.analysis.low.level.api.fir.diagnostics
 
 import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.AbstractKtSourceElement
 import org.jetbrains.kotlin.analysis.low.level.api.fir.util.addValueFor
 import org.jetbrains.kotlin.diagnostics.*
 
 internal class LLFirDiagnosticReporter : DiagnosticReporter() {
-    val diagnostics = mutableMapOf<PsiElement, MutableList<KtPsiDiagnostic>>()
+    private val pendingDiagnostics = mutableMapOf<PsiElement, MutableList<KtPsiDiagnostic>>()
+    val committedDiagnostics = mutableMapOf<PsiElement, MutableList<KtPsiDiagnostic>>()
 
     override fun report(diagnostic: KtDiagnostic?, context: DiagnosticContext) {
         if (diagnostic == null) return
@@ -21,7 +23,31 @@ internal class LLFirDiagnosticReporter : DiagnosticReporter() {
             is KtLightDiagnostic -> diagnostic.toPsiDiagnostic()
             else -> error("Unknown diagnostic type ${diagnostic::class.simpleName}")
         }
-        diagnostics.addValueFor(psiDiagnostic.psiElement, psiDiagnostic)
+        pendingDiagnostics.addValueFor(psiDiagnostic.psiElement, psiDiagnostic)
+    }
+
+    override fun checkAndCommitReportsOn(element: AbstractKtSourceElement, context: DiagnosticContext?) {
+        val commitEverything = context == null
+        for ((diagnosticElement, pendingList) in pendingDiagnostics) {
+            val committedList = committedDiagnostics.getOrPut(diagnosticElement) { mutableListOf() }
+            val iterator = pendingList.iterator()
+            while (iterator.hasNext()) {
+                val diagnostic = iterator.next()
+                when {
+                    context?.isDiagnosticSuppressed(diagnostic as KtDiagnostic) == true -> {
+                        if (diagnostic.element == element ||
+                            diagnostic.element.startOffset >= element.startOffset && diagnostic.element.endOffset <= element.endOffset
+                        ) {
+                            iterator.remove()
+                        }
+                    }
+                    diagnostic.element == element || commitEverything -> {
+                        iterator.remove()
+                        committedList += diagnostic
+                    }
+                }
+            }
+        }
     }
 }