Add support for error binding patterns in the on fail clause

compiler/ballerina-lang/src/main/java/org/ballerinalang/util/diagnostic/DiagnosticErrorCode.java

@@ -468,7 +468,6 @@ public enum DiagnosticErrorCode implements DiagnosticCode {
 
     FAIL_EXPR_NO_MATCHING_ERROR_RETURN_IN_ENCL_INVOKABLE(
             "BCE3035", "fail.expr.no.matching.error.return.in.encl.invokable"),
-    INCOMPATIBLE_ON_FAIL_ERROR_DEFINITION("BCE3036", "on.fail.no.matching.error"),
 
     START_REQUIRE_INVOCATION("BCE3037", "start.require.invocation"),
     INVALID_EXPR_STATEMENT("BCE3038", "invalid.expr.statement"),
@@ -809,7 +808,9 @@ public enum DiagnosticErrorCode implements DiagnosticCode {
     QUERY_CONSTRUCT_TYPES_CANNOT_BE_USED_WITH_COLLECT("BCE4049", "query.construct.types.cannot.be.used.with.collect"),
     VARIABLE_IS_SEQUENCED_MORE_THAN_ONCE("BCE4050", "variable.is.sequenced.more.than.once"),
     INVALID_GROUPING_KEY_TYPE("BCE4051", "invalid.grouping.key.type"),
-    NAMED_ARG_NOT_ALLOWED_FOR_REST_PARAM("BCE4052", "named.arg.not.allowed.for.rest.param")
+    NAMED_ARG_NOT_ALLOWED_FOR_REST_PARAM("BCE4052", "named.arg.not.allowed.for.rest.param"),
+
+    INVALID_BINDING_PATTERN_IN_ON_FAIL("BCS4053", "invalid.binding.pattern.in.on.fail")
     ;
 
     private String diagnosticId;

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/desugar/ASTBuilderUtil.java

@@ -53,6 +53,7 @@
 import org.wso2.ballerinalang.compiler.tree.BLangService;
 import org.wso2.ballerinalang.compiler.tree.BLangSimpleVariable;
 import org.wso2.ballerinalang.compiler.tree.BLangTupleVariable;
+import org.wso2.ballerinalang.compiler.tree.BLangVariable;
 import org.wso2.ballerinalang.compiler.tree.bindingpatterns.BLangBindingPattern;
 import org.wso2.ballerinalang.compiler.tree.bindingpatterns.BLangCaptureBindingPattern;
 import org.wso2.ballerinalang.compiler.tree.clauses.BLangMatchClause;
@@ -552,6 +553,21 @@ static BLangRecordVariableDef createRecordVariableDef(Location pos, BLangRecordV
         return variableDef;
     }
 
+    static BLangErrorVariable createErrorVariable(Location pos, BType type, BLangExpression expr,
+                                                  BLangSimpleVariable message, BLangVariable cause,
+                                                  BLangSimpleVariable restDetail,
+                                                  List<BLangErrorVariable.BLangErrorDetailEntry> detail) {
+        final BLangErrorVariable errVariable = (BLangErrorVariable) TreeBuilder.createErrorVariableNode();
+        errVariable.pos = pos;
+        errVariable.setBType(type);
+        errVariable.expr = expr;
+        errVariable.message = message;
+        errVariable.cause =  cause;
+        errVariable.restDetail = restDetail;
+        errVariable.detail = detail;
+        return errVariable;
+    }
+
     static BLangErrorVariableDef createErrorVariableDef(Location pos, BLangErrorVariable variable) {
         final BLangErrorVariableDef variableDef =
                 (BLangErrorVariableDef) TreeBuilder.createErrorVariableDefinitionNode();

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/desugar/Desugar.java

@@ -5163,18 +5163,8 @@ private BLangFail createOnFailInvocation(BLangOnFailClause onFailClause, BLangFa
         onFailBody.stmts.addAll(onFailClause.body.stmts);
         env.scope.entries.putAll(onFailClause.body.scope.entries);
         onFailBody.failureBreakMode = onFailClause.body.failureBreakMode;
-        VariableDefinitionNode onFailVarDefNode = onFailClause.variableDefinitionNode;
 
-        if (onFailVarDefNode != null) {
-            BVarSymbol onFailErrorVariableSymbol =
-                    ((BLangSimpleVariableDef) onFailVarDefNode).var.symbol;
-            BLangSimpleVariable errorVar = ASTBuilderUtil.createVariable(onFailErrorVariableSymbol.pos,
-                    onFailErrorVariableSymbol.name.value, onFailErrorVariableSymbol.type, rewrite(fail.expr, env),
-                    onFailErrorVariableSymbol);
-            BLangSimpleVariableDef errorVarDef = ASTBuilderUtil.createVariableDef(onFailClause.pos, errorVar);
-            env.scope.define(onFailErrorVariableSymbol.name, onFailErrorVariableSymbol);
-            onFailBody.stmts.add(0, errorVarDef);
-        }
+        handleOnFailErrorVarDefNode(onFailClause.variableDefinitionNode, onFailBody, fail);
 
         if (onFailClause.isInternal && fail.exprStmt != null) {
             if (fail.exprStmt instanceof BLangPanic) {
@@ -5193,6 +5183,37 @@ onFailErrorVariableSymbol.name.value, onFailErrorVariableSymbol.type, rewrite(fa
         return fail;
     }
 
+    private void handleOnFailErrorVarDefNode(VariableDefinitionNode onFailVarDefNode, BLangBlockStmt onFailBody,
+                                             BLangFail fail) {
+        if (onFailVarDefNode == null) {
+            return;
+        }
+
+        BLangVariable variableNode = (BLangVariable) onFailVarDefNode.getVariable();
+        onFailBody.stmts.add(0,
+                             variableNode.getKind() == NodeKind.ERROR_VARIABLE ?
+                                     handleErrorBPInOnFail((BLangErrorVariable) variableNode, fail) :
+                                     handleCaptureBPInOnFail((BLangSimpleVariable) variableNode, fail));
+    }
+
+    private BLangStatement handleErrorBPInOnFail(BLangErrorVariable varNode, BLangFail fail) {
+        BLangErrorVariable errorVar = ASTBuilderUtil.createErrorVariable(varNode.pos,
+                varNode.getBType(), rewrite(fail.expr, env), varNode.message, varNode.cause, varNode.restDetail,
+                varNode.detail);
+        BLangErrorVariableDef errorVarDef = ASTBuilderUtil.createErrorVariableDef(varNode.pos, errorVar);
+        return rewrite(errorVarDef, env);
+    }
+
+    private BLangStatement handleCaptureBPInOnFail(BLangSimpleVariable varNode, BLangFail fail) {
+        BVarSymbol onFailErrorVariableSymbol = varNode.symbol;
+        BLangSimpleVariable errorVar = ASTBuilderUtil.createVariable(onFailErrorVariableSymbol.pos,
+                onFailErrorVariableSymbol.name.value, onFailErrorVariableSymbol.type, rewrite(fail.expr, env),
+                onFailErrorVariableSymbol);
+        BLangSimpleVariableDef errorVarDef = ASTBuilderUtil.createVariableDef(onFailClause.pos, errorVar);
+        env.scope.define(onFailErrorVariableSymbol.name, onFailErrorVariableSymbol);
+        return errorVarDef;
+    }
+
     private BLangBlockStmt rewriteNestedOnFail(BLangOnFailClause onFailClause, BLangFail fail) {
         BLangOnFailClause currentOnFail = this.onFailClause;
 
@@ -5201,18 +5222,8 @@ private BLangBlockStmt rewriteNestedOnFail(BLangOnFailClause onFailClause, BLang
         onFailBody.scope = onFailClause.body.scope;
         onFailBody.mapSymbol = onFailClause.body.mapSymbol;
         onFailBody.failureBreakMode = onFailClause.body.failureBreakMode;
-        VariableDefinitionNode onFailVarDefNode = onFailClause.variableDefinitionNode;
-
-        if (onFailVarDefNode != null) {
-            BVarSymbol onFailErrorVariableSymbol =
-                    ((BLangSimpleVariableDef) onFailVarDefNode).var.symbol;
-            BLangSimpleVariable errorVar = ASTBuilderUtil.createVariable(onFailErrorVariableSymbol.pos,
-                    onFailErrorVariableSymbol.name.value, onFailErrorVariableSymbol.type, rewrite(fail.expr, env),
-                    onFailErrorVariableSymbol);
-            BLangSimpleVariableDef errorVarDef = ASTBuilderUtil.createVariableDef(onFailClause.pos, errorVar);
-            onFailBody.scope.define(onFailErrorVariableSymbol.name, onFailErrorVariableSymbol);
-            onFailBody.stmts.add(0, errorVarDef);
-        }
+
+        handleOnFailErrorVarDefNode(onFailClause.variableDefinitionNode, onFailBody, fail);
 
         int currentOnFailIndex = this.enclosingOnFailClause.indexOf(this.onFailClause);
         int enclosingOnFailIndex = currentOnFailIndex <= 0 ? this.enclosingOnFailClause.size() - 1

compiler/ballerina-lang/src/main/java/org/wso2/ballerinalang/compiler/parser/BLangNodeBuilder.java

@@ -3949,25 +3949,13 @@ public BLangNode transform(OnFailClauseNode onFailClauseNode) {
         Location pos = getPosition(onFailClauseNode);
         BLangOnFailClause onFailClause = (BLangOnFailClause) TreeBuilder.createOnFailClauseNode();
         onFailClause.pos = pos;
-        onFailClauseNode.typeDescriptor().ifPresent(typeDescriptorNode -> {
-            BLangSimpleVariableDef variableDefinitionNode =
-                    (BLangSimpleVariableDef) TreeBuilder.createSimpleVariableDefinitionNode();
-            BLangSimpleVariable var = (BLangSimpleVariable) TreeBuilder.createSimpleVariableNode();
-            boolean isDeclaredWithVar = typeDescriptorNode.kind() == SyntaxKind.VAR_TYPE_DESC;
-            var.isDeclaredWithVar = isDeclaredWithVar;
-            if (!isDeclaredWithVar) {
-                var.setTypeNode(createTypeNode(typeDescriptorNode));
-            }
-            var.pos = pos;
-            onFailClauseNode.failErrorName().ifPresent(identifierToken -> {
-                var.setName(this.createIdentifier(identifierToken));
-                var.name.pos = getPosition(identifierToken);
-                variableDefinitionNode.setVariable(var);
-                variableDefinitionNode.pos = getPosition(typeDescriptorNode,
-                        identifierToken);
-            });
-            onFailClause.isDeclaredWithVar = isDeclaredWithVar;
-            markVariableWithFlag(variableDefinitionNode.getVariable(), Flag.FINAL);
+        onFailClauseNode.typedBindingPattern().ifPresent(typedBindingPatternNode -> {
+            VariableDefinitionNode variableDefinitionNode =
+                    createBLangVarDef(getPosition(typedBindingPatternNode), typedBindingPatternNode,
+                            Optional.empty(), Optional.empty());
+            onFailClause.isDeclaredWithVar =
+                    typedBindingPatternNode.typeDescriptor().kind() == SyntaxKind.VAR_TYPE_DESC;
+            markVariableWithFlag((BLangVariable) variableDefinitionNode.getVariable(), Flag.FINAL);
             onFailClause.variableDefinitionNode = variableDefinitionNode;
         });
         BLangBlockStmt blockNode = (BLangBlockStmt) transform(onFailClauseNode.blockStatement());