GROOVY-11964: Additional multi-assignment forms

Author: paulk-asert

src/antlr/GroovyParser.g4

@@ -578,10 +578,15 @@ variableDeclaration[int t]
 
 typeNamePairs
     :   LPAREN typeNamePair (COMMA typeNamePair)* RPAREN
+    |   LPAREN keyedPair (COMMA keyedPair)* RPAREN
     ;
 
 typeNamePair
-    :   type? variableDeclaratorId
+    :   (DEF | VAR | type)? MUL? variableDeclaratorId
+    ;
+
+keyedPair
+    :   key=identifier COLON (DEF | VAR | type)? variableDeclaratorId
     ;
 
 variableNames

src/main/java/org/apache/groovy/parser/antlr4/AstBuilder.java

@@ -56,6 +56,7 @@
 import org.codehaus.groovy.ast.FieldNode;
 import org.codehaus.groovy.ast.GenericsType;
 import org.codehaus.groovy.ast.ImportNode;
+import org.codehaus.groovy.ast.MultipleAssignmentMetadata;
 import org.codehaus.groovy.ast.InnerClassNode;
 import org.codehaus.groovy.ast.MethodNode;
 import org.codehaus.groovy.ast.ModifierNode;
@@ -2205,16 +2206,56 @@ private boolean isFieldDeclaration(final ModifierManager modifierManager, final
 
     @Override
     public List<Expression> visitTypeNamePairs(final TypeNamePairsContext ctx) {
-        return ctx.typeNamePair().stream().map(this::visitTypeNamePair).collect(Collectors.toList());
+        if (asBoolean(ctx.keyedPair())) { // GEP-20 map-style: def (name: n, age: a) = person
+            return ctx.keyedPair().stream().map(this::visitKeyedPair).collect(Collectors.toList());
+        }
+        List<Expression> pairs = ctx.typeNamePair().stream().map(this::visitTypeNamePair).collect(Collectors.toList());
+        // GEP-20: at most one rest binding (*) per parens form
+        boolean seenRest = false;
+        for (Expression e : pairs) {
+            if (Boolean.TRUE.equals(e.getNodeMetaData(MultipleAssignmentMetadata.REST_BINDING))) {
+                if (seenRest) {
+                    throw createParsingFailedException("Only one rest binding (*) is allowed in a multi-assignment", e);
+                }
+                seenRest = true;
+            }
+        }
+        return pairs;
     }
 
     @Override
     public VariableExpression visitTypeNamePair(final TypeNamePairContext ctx) {
-        return configureAST(
+        boolean isRest = asBoolean(ctx.MUL());
+        // GEP-20: typed rest (e.g. `def (h, List<Integer> *t) = list`) is accepted; the
+        // declared container type is honoured by static type checking and runtime coercion.
+        // `def` and `var` are also accepted in place of a type (equivalent to omitting it),
+        // for symmetry with switch case patterns and the bracket-form declaration grammar.
+        VariableExpression ve = configureAST(
                 new VariableExpression(
                         this.visitVariableDeclaratorId(ctx.variableDeclaratorId()).getName(),
-                        this.visitType(ctx.type())),
+                        binderType(ctx.DEF(), ctx.VAR(), ctx.type())),
                 ctx);
+        if (isRest) {
+            ve.putNodeMetaData(MultipleAssignmentMetadata.REST_BINDING, Boolean.TRUE);
+        }
+        return ve;
+    }
+
+    @Override
+    public VariableExpression visitKeyedPair(final KeyedPairContext ctx) {
+        VariableExpression ve = configureAST(
+                new VariableExpression(
+                        this.visitVariableDeclaratorId(ctx.variableDeclaratorId()).getName(),
+                        binderType(ctx.DEF(), ctx.VAR(), ctx.type())),
+                ctx);
+        ve.putNodeMetaData(MultipleAssignmentMetadata.MAP_KEY, this.visitIdentifier(ctx.key));
+        return ve;
+    }
+
+    /** GEP-20: resolve a binder's declared type — `def`/`var` produce the dynamic type, same as omitting a type. */
+    private ClassNode binderType(final TerminalNode defNode, final TerminalNode varNode, final TypeContext typeCtx) {
+        if (asBoolean(defNode) || asBoolean(varNode)) return ClassHelper.dynamicType();
+        return this.visitType(typeCtx);
     }
 
     @Override

src/main/java/org/codehaus/groovy/ast/MultipleAssignmentMetadata.java

@@ -0,0 +1,32 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package org.codehaus.groovy.ast;
+
+/**
+ * AST node metadata keys used by the multi-assignment destructuring pipeline
+ * introduced in GEP-20. Each key is attached to a {@code VariableExpression}
+ * appearing inside the {@code TupleExpression} on the LHS of a
+ * {@code DeclarationExpression}.
+ */
+public enum MultipleAssignmentMetadata {
+    /** Marker on the rest binder (the {@code *ident} slot). Value is {@link Boolean#TRUE}. */
+    REST_BINDING,
+    /** Value is the key name (String) used for a map-style {@code key: ident} binder. */
+    MAP_KEY
+}

src/main/java/org/codehaus/groovy/classgen/asm/BinaryExpressionHelper.java

@@ -21,6 +21,7 @@
 import org.codehaus.groovy.GroovyBugError;
 import org.codehaus.groovy.ast.ClassHelper;
 import org.codehaus.groovy.ast.ClassNode;
+import org.codehaus.groovy.ast.MultipleAssignmentMetadata;
 import org.codehaus.groovy.ast.Variable;
 import org.codehaus.groovy.ast.expr.ArrayExpression;
 import org.codehaus.groovy.ast.expr.BinaryExpression;
@@ -43,6 +44,7 @@
 import org.codehaus.groovy.ast.tools.WideningCategories;
 import org.codehaus.groovy.classgen.AsmClassGenerator;
 import org.codehaus.groovy.classgen.BytecodeExpression;
+import org.codehaus.groovy.runtime.MultipleAssignmentSupport;
 import org.codehaus.groovy.runtime.ScriptBytecodeAdapter;
 import org.codehaus.groovy.syntax.Token;
 import org.objectweb.asm.Label;
@@ -53,10 +55,12 @@
 import static org.codehaus.groovy.ast.tools.GeneralUtils.binX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.boolX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.callX;
+import static org.codehaus.groovy.ast.tools.GeneralUtils.classX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.constX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.elvisX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.notX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.nullX;
+import static org.codehaus.groovy.ast.tools.GeneralUtils.propX;
 import static org.codehaus.groovy.ast.tools.GeneralUtils.ternaryX;
 import static org.codehaus.groovy.syntax.Types.ASSIGN;
 import static org.codehaus.groovy.syntax.Types.BITWISE_AND;
@@ -505,6 +509,101 @@ public void evaluateEqual(final BinaryExpression expression, final boolean defin
             leftExpression.visit(acg);
             operandStack.remove(operandStack.getStackLength() - mark);
         } else { // multiple declaration or assignment
+            TupleExpression tuple = (TupleExpression) leftExpression;
+            java.util.List<Expression> elements = tuple.getExpressions();
+            int tupleSize = elements.size();
+            int restIndex = -1;
+            for (int idx = 0; idx < tupleSize; idx++) {
+                if (Boolean.TRUE.equals(elements.get(idx).getNodeMetaData(MultipleAssignmentMetadata.REST_BINDING))) {
+                    restIndex = idx;
+                    break;
+                }
+            }
+            boolean hasRest = (restIndex >= 0);
+            boolean tailRest = hasRest && restIndex == tupleSize - 1;
+            boolean isMapStyle = !elements.isEmpty()
+                    && elements.get(0).getNodeMetaData(MultipleAssignmentMetadata.MAP_KEY) != null;
+
+            // GEP-20 map-style destructuring: def (name: n, age: a) = person
+            // Each binder is emitted as a property access on the RHS, dispatched via the MOP
+            // (Map → key lookup, bean → getter, GroovyObject → getProperty).
+            if (isMapStyle) {
+                for (Expression e : elements) {
+                    String key = (String) e.getNodeMetaData(MultipleAssignmentMetadata.MAP_KEY);
+                    // Property access is a read here; the surrounding pushLHS(true) above would
+                    // otherwise mark it as a store target.
+                    compileStack.popLHS();
+                    propX(rhsValueLoader, key).visit(acg);
+                    compileStack.pushLHS(true);
+                    assignOneMultiAssignSlot(e, defineVariable, operandStack, compileStack, acg);
+                }
+                compileStack.popLHS();
+                if (returnRightValue) rhsValueLoader.visit(acg);
+                compileStack.removeVar(rhsValueId);
+                return;
+            }
+
+            // GEP-20 degenerate case: `def (*t) = rhs` — single rest binder; equivalent to `def t = rhs`.
+            if (tailRest && tupleSize == 1) {
+                rhsValueLoader.visit(acg);
+                if (defineVariable) {
+                    Variable v = (Variable) elements.get(0);
+                    operandStack.doGroovyCast(v);
+                    compileStack.defineVariable(v, true);
+                    operandStack.remove(1);
+                } else {
+                    elements.get(0).visit(acg);
+                }
+                compileStack.popLHS();
+                if (returnRightValue) rhsValueLoader.visit(acg);
+                compileStack.removeVar(rhsValueId);
+                return;
+            }
+
+            // GEP-20 head/middle rest: def (*f, last) = list, def (l, *m, r) = list, etc.
+            // Requires a sized, indexable RHS (Path B only — no iterator fallback).
+            // Load-bearing ordering (GEP lines 177-186): the IntRange call for the rest slot
+            // must be emitted BEFORE any negative-index call, so that an iterator/stream RHS
+            // fails fast with MissingMethodException instead of hanging via materialisation.
+            if (hasRest && !tailRest) {
+                // 1. Emit the IntRange call for the rest slot first, via the helper that
+                //    returns an empty slice for inverted ranges (short RHS) and fails fast
+                //    for non-indexable RHS (iterator/stream/set), per GEP lines 177-186.
+                // Number of fixed slots after the rest = tupleSize - restIndex - 1; their negative
+                // indices span [-k, -1]; the rest slice therefore ends at -(k+1) = -(tupleSize - restIndex).
+                // e.g. def (*f,last): -2; def (l,*m,r): -2; def (a,b,*m,y,z): -3
+                int toIdx = -(tupleSize - restIndex);
+                MethodCallExpression sliceCall = callX(
+                        classX(MultipleAssignmentSupport.class),
+                        "nonTailRestSlice",
+                        args(rhsValueLoader, constX(restIndex, true), constX(toIdx, true)));
+                sliceCall.setImplicitThis(false);
+                sliceCall.visit(acg);
+                assignOneMultiAssignSlot(elements.get(restIndex), defineVariable, operandStack, compileStack, acg);
+
+                // 2. Positive-index fixed slots (before rest), left-to-right.
+                for (int idx = 0; idx < restIndex; idx++) {
+                    MethodCallExpression call = callX(rhsValueLoader, "getAt", constX(idx, true));
+                    call.setImplicitThis(false);
+                    call.visit(acg);
+                    assignOneMultiAssignSlot(elements.get(idx), defineVariable, operandStack, compileStack, acg);
+                }
+
+                // 3. Negative-index fixed slots (after rest), left-to-right.
+                for (int idx = restIndex + 1; idx < tupleSize; idx++) {
+                    int negIdx = -(tupleSize - idx);
+                    MethodCallExpression call = callX(rhsValueLoader, "getAt", constX(negIdx, true));
+                    call.setImplicitThis(false);
+                    call.visit(acg);
+                    assignOneMultiAssignSlot(elements.get(idx), defineVariable, operandStack, compileStack, acg);
+                }
+
+                compileStack.popLHS();
+                if (returnRightValue) rhsValueLoader.visit(acg);
+                compileStack.removeVar(rhsValueId);
+                return;
+            }
+
             MethodCallExpression iterator = callX(rhsValueLoader, "iterator");
             iterator.setImplicitThis(false);
             iterator.visit(acg);
@@ -529,9 +628,17 @@ public void evaluateEqual(final BinaryExpression expression, final boolean defin
             mv.visitJumpInsn(IF_ACMPEQ, useGetAt);
 
             boolean first = true;
-            for (Expression e : (TupleExpression) leftExpression) {
-                if (first) {
-                    first = false;
+            for (int idx = 0; idx < tupleSize; idx++) {
+                Expression e = elements.get(idx);
+                if (idx == restIndex) { // tail rest: dispatch Path B (slice) vs Path C (iterator) at runtime
+                    MethodCallExpression restCall = callX(
+                            classX(MultipleAssignmentSupport.class),
+                            "tailRest",
+                            args(rhsValueLoader, constX(idx, true), seq));
+                    restCall.setImplicitThis(false);
+                    restCall.visit(acg);
+                } else if (first) {
+                    first = false; // value already on stack from next() above
                 } else {
                     ternaryX(hasNext, next, nullX()).visit(acg);
                 }
@@ -553,11 +660,19 @@ public void evaluateEqual(final BinaryExpression expression, final boolean defin
 
             mv.visitLabel(useGetAt_noPop);
 
-            int i = 0;
-            for (Expression e : (TupleExpression) leftExpression) {
-                MethodCallExpression getAt = callX(rhsValueLoader, "getAt", constX(i++, true));
-                getAt.setImplicitThis(false);
-                getAt.visit(acg);
+            for (int idx = 0; idx < tupleSize; idx++) {
+                Expression e = elements.get(idx);
+                MethodCallExpression call;
+                if (idx == restIndex) { // tail rest: dispatch via helper so empty RHS / non-indexable cases are handled uniformly
+                    call = callX(
+                            classX(MultipleAssignmentSupport.class),
+                            "tailRest",
+                            args(rhsValueLoader, constX(idx, true), seq));
+                } else {
+                    call = callX(rhsValueLoader, "getAt", constX(idx, true));
+                }
+                call.setImplicitThis(false);
+                call.visit(acg);
 
                 if (defineVariable) {
                     Variable v = (Variable) e;
@@ -585,6 +700,20 @@ public void evaluateEqual(final BinaryExpression expression, final boolean defin
         compileStack.removeVar(rhsValueId);
     }
 
+    /** GEP-20: assign the single value currently on the operand stack to the given declarator slot. */
+    private void assignOneMultiAssignSlot(final Expression e, final boolean defineVariable,
+                                          final OperandStack operandStack, final CompileStack compileStack,
+                                          final AsmClassGenerator acg) {
+        if (defineVariable) {
+            Variable v = (Variable) e;
+            operandStack.doGroovyCast(v);
+            compileStack.defineVariable(v, true);
+            operandStack.remove(1);
+        } else {
+            e.visit(acg);
+        }
+    }
+
     protected void evaluateCompareExpression(final MethodCaller compareMethod, final BinaryExpression expression) {
         Expression leftExp = expression.getLeftExpression();
         Expression rightExp = expression.getRightExpression();