[FIR-IDE] Changes after review

Move usage of SingleCandidateResolver into dedicated component from KtFirAnalysisSession.
Add validity assertion, use concurrent map for context cache, provide original PSI when building context.
Update names, make other minor changes.

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/KtAnalysisSession.kt

@@ -40,6 +40,7 @@ abstract class KtAnalysisSession(override val token: ValidityToken) : ValidityTo
     protected abstract val containingDeclarationProvider: KtSymbolContainingDeclarationProvider
     protected abstract val symbolProvider: KtSymbolProvider
     protected abstract val callResolver: KtCallResolver
+    protected abstract val completionCandidateChecker: KtCompletionCandidateChecker
 
 
     /// TODO: get rid of
@@ -119,10 +120,16 @@ abstract class KtAnalysisSession(override val token: ValidityToken) : ValidityTo
         return resolveToSymbols().singleOrNull()
     }
 
-    abstract fun resolveAndCheckReceivers(
-        firSymbolForCandidate: KtCallableSymbol,
-        originalFile: KtFile,
-        nameExpression: KtSimpleNameExpression,
-        possibleReceiver: KtExpression?,
-    ): Boolean
+    fun KtCallableSymbol.checkExtensionIsSuitable(
+        originalPsiFile: KtFile,
+        originalPosition: PsiElement?,
+        psiFakeCompletionExpression: KtSimpleNameExpression,
+        psiReceiverExpression: KtExpression?,
+    ): Boolean = completionCandidateChecker.checkExtensionFitsCandidate(
+        this,
+        originalPsiFile,
+        originalPosition,
+        psiFakeCompletionExpression,
+        psiReceiverExpression
+    )
 }

idea/idea-frontend-api/src/org/jetbrains/kotlin/idea/frontend/api/components/KtCompletionCandidateChecker.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.frontend.api.components
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
+import org.jetbrains.kotlin.psi.KtExpression
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.psi.KtSimpleNameExpression
+
+abstract class KtCompletionCandidateChecker : KtAnalysisSessionComponent() {
+    abstract fun checkExtensionFitsCandidate(
+        firSymbolForCandidate: KtCallableSymbol,
+        originalFile: KtFile,
+        originalPosition: PsiElement?,
+        nameExpression: KtSimpleNameExpression,
+        possibleExplicitReceiver: KtExpression?,
+    ): Boolean
+}