LT: make where clause with errors parsing same as with PSI

- do not fail on the missing terms
- propagate invalid name to avoid reporting dangling constraints

#KT-58455 fixed

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java

@@ -13972,6 +13972,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/tests/generics/unresolvedClassifierInWhere.kt");
             }
 
+            @Test
+            @TestMetadata("whereClauseSyntax.kt")
+            public void testWhereClauseSyntax() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/whereClauseSyntax.kt");
+            }
+
             @Test
             @TestMetadata("wildcardInValueParameter.kt")
             public void testWildcardInValueParameter() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java

@@ -13972,6 +13972,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/tests/generics/unresolvedClassifierInWhere.kt");
             }
 
+            @Test
+            @TestMetadata("whereClauseSyntax.kt")
+            public void testWhereClauseSyntax() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/whereClauseSyntax.kt");
+            }
+
             @Test
             @TestMetadata("wildcardInValueParameter.kt")
             public void testWildcardInValueParameter() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java

@@ -13966,6 +13966,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                 runTest("compiler/testData/diagnostics/tests/generics/unresolvedClassifierInWhere.kt");
             }
 
+            @Test
+            @TestMetadata("whereClauseSyntax.kt")
+            public void testWhereClauseSyntax() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/whereClauseSyntax.kt");
+            }
+
             @Test
             @TestMetadata("wildcardInValueParameter.kt")
             public void testWildcardInValueParameter() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java

@@ -13972,6 +13972,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                 runTest("compiler/testData/diagnostics/tests/generics/unresolvedClassifierInWhere.kt");
             }
 
+            @Test
+            @TestMetadata("whereClauseSyntax.kt")
+            public void testWhereClauseSyntax() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/whereClauseSyntax.kt");
+            }
+
             @Test
             @TestMetadata("wildcardInValueParameter.kt")
             public void testWildcardInValueParameter() throws Exception {

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirDeclarationBuilder.kt

@@ -1975,18 +1975,22 @@ class LightTreeRawFirDeclarationBuilder(
      * @see org.jetbrains.kotlin.parsing.KotlinParsing.parseTypeConstraint
      */
     private fun convertTypeConstraint(typeConstraint: LighterASTNode): TypeConstraint {
-        lateinit var identifier: String
+        var identifier: String? = null
-        lateinit var firType: FirTypeRef
+        var firType: FirTypeRef? = null
-        lateinit var referenceExpression: LighterASTNode
+        var referenceExpression: LighterASTNode? = null
-
-        val diagnostic = ConeSimpleDiagnostic(
-            "Type parameter annotations are not allowed inside where clauses", DiagnosticKind.AnnotationNotAllowed,
-        )
 
         val annotations = mutableListOf<FirAnnotation>()
         typeConstraint.forEachChildren {
             when (it.tokenType) {
-                ANNOTATION_ENTRY -> annotations += convertAnnotationEntry(it, diagnostic = diagnostic)
+                ANNOTATION_ENTRY -> {
+                    annotations +=
+                        convertAnnotationEntry(
+                            it,
+                            diagnostic = ConeSimpleDiagnostic(
+                                "Type parameter annotations are not allowed inside where clauses", DiagnosticKind.AnnotationNotAllowed,
+                            )
+                        )
+                }
                 REFERENCE_EXPRESSION -> {
                     identifier = it.asText
                     referenceExpression = it
@@ -1995,7 +1999,12 @@ class LightTreeRawFirDeclarationBuilder(
             }
         }
 
-        return TypeConstraint(annotations, identifier, firType, referenceExpression.toFirSourceElement())
+        return TypeConstraint(
+            annotations,
+            identifier,
+            firType ?: buildErrorTypeRef { },
+            (referenceExpression ?: typeConstraint).toFirSourceElement()
+        )
     }
 
     /**
@@ -2391,8 +2400,8 @@ class LightTreeRawFirDeclarationBuilder(
     ) where T : FirDeclaration, T : FirTypeParameterRefsOwner {
         val typeParamNames = typeParameters.map { it.name }.toSet()
         val result = typeConstraints.mapNotNull { constraint ->
-            val name = constraint.identifier.nameAsSafeName()
+            val name = constraint.identifier?.nameAsSafeName()
-            if (!typeParamNames.contains(name)) {
+            if (name != null && !typeParamNames.contains(name)) {
                 DanglingTypeConstraint(name, constraint.source)
             } else {
                 null

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/fir/TypeConstraint.kt

@@ -11,7 +11,7 @@ import org.jetbrains.kotlin.fir.types.FirTypeRef
 
 class TypeConstraint(
     val annotations: List<FirAnnotation>,
-    val identifier: String,
+    val identifier: String?,
     val firTypeRef: FirTypeRef,
     val source: KtSourceElement
 )

compiler/testData/diagnostics/tests/generics/whereClauseSyntax.fir.kt

@@ -0,0 +1,6 @@
+// DIAGNOSTICS: -DEBUG_INFO_MISSING_UNRESOLVED
+interface I
+fun <E> foo() where E: I {}
+fun <E> fooE1() where <!SYNTAX!><!>: I {}
+fun <E> fooE2() where E: <!SYNTAX, SYNTAX!><!>{}
+fun <E> fooE3() where <!SYNTAX!><!>{}

compiler/testData/diagnostics/tests/generics/whereClauseSyntax.kt

@@ -0,0 +1,6 @@
+// DIAGNOSTICS: -DEBUG_INFO_MISSING_UNRESOLVED
+interface I
+fun <E> foo() where E: I {}
+fun <E> fooE1() where <!SYNTAX!><!>: I {}
+fun <E> fooE2() where E: <!SYNTAX!><!>{}
+fun <E> fooE3() where <!SYNTAX!><!>{}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -13972,6 +13972,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/generics/unresolvedClassifierInWhere.kt");
             }
 
+            @Test
+            @TestMetadata("whereClauseSyntax.kt")
+            public void testWhereClauseSyntax() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/whereClauseSyntax.kt");
+            }
+
             @Test
             @TestMetadata("wildcardInValueParameter.kt")
             public void testWildcardInValueParameter() throws Exception {