Commit trace for callable reference's LHS with reserved syntax like foo?::bar?::bar to avoid the lack of diagnostics reporting

^KT-35075 Fixed

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirOldFrontendDiagnosticsTestGenerated.java

@@ -1999,6 +1999,11 @@ public class FirOldFrontendDiagnosticsTestGenerated extends AbstractFirOldFronte
             runTest("compiler/testData/diagnostics/tests/callableReference/whitespacesInExpression.kt");
         }
 
+        @TestMetadata("withQuestionMarks.kt")
+        public void testWithQuestionMarks() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/callableReference/withQuestionMarks.kt");
+        }
+
         @TestMetadata("compiler/testData/diagnostics/tests/callableReference/bound")
         @TestDataPath("$PROJECT_ROOT")
         @RunWith(JUnit3RunnerWithInners.class)

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/DoubleColonExpressionResolver.kt

@@ -325,7 +325,7 @@ class DoubleColonExpressionResolver(
     }
 
     private fun resolveReservedExpressionSyntaxOnDoubleColonLHS(doubleColonExpression: KtDoubleColonExpression, c: ExpressionTypingContext):
-            Pair<Boolean, DoubleColonLHS?> {
+            ReservedDoubleColonLHSResolutionResult {
         val resultForReservedExpr = tryResolveLHS(
             doubleColonExpression, c,
             this::shouldTryResolveLHSAsReservedExpression,
@@ -335,7 +335,7 @@ class DoubleColonExpressionResolver(
             val lhs = resultForReservedExpr.lhs
             if (lhs != null) {
                 c.trace.report(RESERVED_SYNTAX_IN_CALLABLE_REFERENCE_LHS.on(resultForReservedExpr.expression))
-                return Pair(true, resultForReservedExpr.commit())
+                return ReservedDoubleColonLHSResolutionResult(true, resultForReservedExpr.commit(), resultForReservedExpr.traceAndCache)
             }
         }
 
@@ -349,11 +349,13 @@ class DoubleColonExpressionResolver(
             if (lhs != null) {
                 c.trace.report(RESERVED_SYNTAX_IN_CALLABLE_REFERENCE_LHS.on(resultForReservedCallChain.expression))
                 // DO NOT commit trace from resultForReservedCallChain here
-                return Pair(true, null)
+                return ReservedDoubleColonLHSResolutionResult(true, null, resultForReservedExpr?.traceAndCache)
             }
         }
 
-        return Pair(false, null)
+        return ReservedDoubleColonLHSResolutionResult(
+            false, null, resultForReservedExpr?.traceAndCache ?: resultForReservedCallChain?.traceAndCache
+        )
     }
 
     internal fun resolveDoubleColonLHS(doubleColonExpression: KtDoubleColonExpression, c: ExpressionTypingContext): DoubleColonLHS? {
@@ -367,7 +369,9 @@ class DoubleColonExpressionResolver(
             }
         }
 
-        val (isReservedExpressionSyntax, doubleColonLHS) = resolveReservedExpressionSyntaxOnDoubleColonLHS(doubleColonExpression, c)
+        val (isReservedExpressionSyntax, doubleColonLHS, traceAndCacheFromReservedDoubleColonLHS) =
+            resolveReservedExpressionSyntaxOnDoubleColonLHS(doubleColonExpression, c)
+
         if (isReservedExpressionSyntax) return doubleColonLHS
 
         val resultForType = tryResolveLHS(doubleColonExpression, c, this::shouldTryResolveLHSAsType) { expression, context ->
@@ -390,14 +394,25 @@ class DoubleColonExpressionResolver(
             }
         }
 
-        // If the LHS could be resolved neither as an expression nor as a type, we should still type-check it to allow all diagnostics
-        // to be reported and references to be resolved. For that, we commit one of the applicable traces here, preferring the expression
         if (resultForExpr != null) return resultForExpr.commit()
         if (resultForType != null) return resultForType.commit()
 
+        /*
+         * If the LHS could be resolved neither as an expression nor as a type,
+         * but it was resolved as expression with reserved syntax like `foo?::bar?::bar`,
+         * then we commit the trace of that resolution result.
+         */
+        traceAndCacheFromReservedDoubleColonLHS?.commit()
+
         return null
     }
 
+    private data class ReservedDoubleColonLHSResolutionResult(
+        val isReservedExpressionSyntax: Boolean,
+        val lhs: DoubleColonLHS?,
+        val traceAndCache: TemporaryTraceAndCache?
+    )
+
     private class LHSResolutionResult<out T : DoubleColonLHS>(
         val lhs: T?,
         val expression: KtExpression,

compiler/testData/diagnostics/tests/callableReference/withQuestionMarks.fir.kt

@@ -0,0 +1,31 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// Issue: KT-35075
+
+fun foo() {}
+
+fun main() {
+    val x1 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>::info<!>?::print<!>
+    val x2 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>?::info<!>?::print<!>
+    val x3 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>?::info<!>::print<!>
+    val x4 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>?::info<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>
+    val x5 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>::info<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>?::print<!>
+    val x6 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>!!::info<!>?::print<!>?::print<!>
+    val x7 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>::info!!::print<!>?::print<!>
+    val x8 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>?::info!!::print<!>?::print<!>
+    val x9 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>!!::info<!>?::print<!>?::print<!>
+    val x10 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>::info<!>?::print!!::print<!>
+    val x11 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>!!::info!!::print!!::print<!>
+    val x12 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>?::info!!::print!!::print<!>
+    val x13 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>42?::unresolved<!>?::print<!>
+
+    val x14 = <!UNRESOLVED_REFERENCE!>logger<!><!SYNTAX!>?!!::info?::print?::print<!>
+    val x15 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>::info<!><!SYNTAX!>?!!::print?::print<!>
+    val x16 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>!!?::info<!>?::print<!>?::print<!>
+    val x17 = <!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!><!UNRESOLVED_REFERENCE!>logger<!>::info!!?::print<!>?::print<!>
+
+    // It must be OK
+    val x18 = String?::hashCode ?: ::foo
+    val x19 = String::hashCode ?: ::foo
+    val x20 = String?::hashCode::hashCode
+    val x21 = kotlin.String?::hashCode::hashCode
+}

compiler/testData/diagnostics/tests/callableReference/withQuestionMarks.kt

@@ -0,0 +1,31 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// Issue: KT-35075
+
+fun foo() {}
+
+fun main() {
+    val x1 = <!UNRESOLVED_REFERENCE!>logger<!>::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x2 = <!UNRESOLVED_REFERENCE!>logger<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x3 = <!UNRESOLVED_REFERENCE!>logger<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x4 = <!UNRESOLVED_REFERENCE!>logger<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x5 = <!UNRESOLVED_REFERENCE!>logger<!>::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x6 = <!UNRESOLVED_REFERENCE!>logger<!>!!::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x7 = <!UNRESOLVED_REFERENCE!>logger<!>::<!UNRESOLVED_REFERENCE!>info<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!OVERLOAD_RESOLUTION_AMBIGUITY!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x8 = <!UNRESOLVED_REFERENCE!>logger<!>?::<!UNRESOLVED_REFERENCE!>info<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!OVERLOAD_RESOLUTION_AMBIGUITY!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x9 = <!UNRESOLVED_REFERENCE!>logger<!>!!::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x10 = <!UNRESOLVED_REFERENCE!>logger<!>::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!UNRESOLVED_REFERENCE!>print<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!OVERLOAD_RESOLUTION_AMBIGUITY!>print<!>
+    val x11 = <!UNRESOLVED_REFERENCE!>logger<!>!!::<!UNRESOLVED_REFERENCE!>info<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!CALLABLE_REFERENCE_RESOLUTION_AMBIGUITY!>print<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!OVERLOAD_RESOLUTION_AMBIGUITY!>print<!>
+    val x12 = <!UNRESOLVED_REFERENCE!>logger<!>?::<!UNRESOLVED_REFERENCE!>info<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!CALLABLE_REFERENCE_RESOLUTION_AMBIGUITY!>print<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!>::<!OVERLOAD_RESOLUTION_AMBIGUITY!>print<!>
+    val x13 = <!RESERVED_SYNTAX_IN_CALLABLE_REFERENCE_LHS!>42<!>?::<!UNRESOLVED_REFERENCE!>unresolved<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+
+    val x14 = <!UNRESOLVED_REFERENCE!>logger<!><!SYNTAX!>?!!::info?::print?::print<!>
+    val x15 = <!UNRESOLVED_REFERENCE!>logger<!>::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!><!SYNTAX!>?!!::print?::print<!>
+    val x16 = <!UNRESOLVED_REFERENCE!>logger<!>!!?::<!DEBUG_INFO_MISSING_UNRESOLVED!>info<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+    val x17 = <!RESERVED_SYNTAX_IN_CALLABLE_REFERENCE_LHS!><!UNRESOLVED_REFERENCE!>logger<!>::<!UNRESOLVED_REFERENCE!>info<!><!NOT_NULL_ASSERTION_ON_CALLABLE_REFERENCE!>!!<!><!>?::<!OVERLOAD_RESOLUTION_AMBIGUITY!>print<!>?::<!DEBUG_INFO_MISSING_UNRESOLVED!>print<!>
+
+    // It must be OK
+    val x18 = String?::hashCode <!USELESS_ELVIS!>?: ::foo<!>
+    val x19 = String::hashCode <!USELESS_ELVIS!>?: ::foo<!>
+    val x20 = String?::<!UNSAFE_CALL!>hashCode<!>::hashCode
+    val x21 = kotlin.String?::<!UNSAFE_CALL!>hashCode<!>::hashCode
+}

compiler/testData/diagnostics/tests/callableReference/withQuestionMarks.txt

@@ -0,0 +1,4 @@
+package
+
+public fun foo(): kotlin.Unit
+public fun main(): kotlin.Unit

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -2006,6 +2006,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTestWithFirVali
                 runTest("compiler/testData/diagnostics/tests/callableReference/whitespacesInExpression.kt");
             }
 
+            @TestMetadata("withQuestionMarks.kt")
+            public void testWithQuestionMarks() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/callableReference/withQuestionMarks.kt");
+            }
+
             @TestMetadata("compiler/testData/diagnostics/tests/callableReference/bound")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -2001,6 +2001,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/callableReference/whitespacesInExpression.kt");
             }
 
+            @TestMetadata("withQuestionMarks.kt")
+            public void testWithQuestionMarks() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/callableReference/withQuestionMarks.kt");
+            }
+
             @TestMetadata("compiler/testData/diagnostics/tests/callableReference/bound")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)