[WIP][Experimental][Known to fail] Rewire lambda expression in the proper place in the grammar hierarchy

org.eclipse.jdt.core.compiler.batch/grammar/java.g

@@ -1751,7 +1751,6 @@ PrimaryNoNewArray -> ArrayAccess
 --                   Start of rules for JSR 335
 -----------------------------------------------------------------------
 
-PrimaryNoNewArray -> LambdaExpression
 PrimaryNoNewArray -> ReferenceExpression
 /:$readableName Expression:/
 
@@ -2083,6 +2082,17 @@ CastExpression ::=  BeginIntersectionCast PushLPAREN CastNameAndBounds PushRPARE
 /.$putCase consumeCastExpressionLL1WithBounds(); $break ./
 CastExpression ::= PushLPAREN Name Dims AdditionalBoundsListOpt PushRPAREN InsideCastExpression UnaryExpressionNotPlusMinus
 /.$putCase consumeCastExpressionWithNameArray(); $break ./
+--------
+CastExpression ::= PushLPAREN Name OnlyTypeArgumentsForCastExpression Dimsopt AdditionalBoundsListOpt PushRPAREN InsideCastExpression LambdaExpression
+/.$putCase consumeCastExpressionWithGenericsArray(); $break ./
+CastExpression ::= PushLPAREN Name OnlyTypeArgumentsForCastExpression '.' ClassOrInterfaceType Dimsopt AdditionalBoundsListOpt PushRPAREN InsideCastExpressionWithQualifiedGenerics LambdaExpression
+/.$putCase consumeCastExpressionWithQualifiedGenericsArray(); $break ./
+CastExpression ::= PushLPAREN Name PushRPAREN InsideCastExpressionLL1 LambdaExpression
+/.$putCase consumeCastExpressionLL1(); $break ./
+CastExpression ::=  BeginIntersectionCast PushLPAREN CastNameAndBounds PushRPAREN InsideCastExpressionLL1WithBounds LambdaExpression
+/.$putCase consumeCastExpressionLL1WithBounds(); $break ./
+CastExpression ::= PushLPAREN Name Dims AdditionalBoundsListOpt PushRPAREN InsideCastExpression LambdaExpression
+/.$putCase consumeCastExpressionWithNameArray(); $break ./
 /:$readableName CastExpression:/
 
 AdditionalBoundsListOpt ::= $empty
@@ -2188,14 +2198,16 @@ ConditionalOrExpression ::= ConditionalOrExpression '||' ConditionalAndExpressio
 ConditionalExpression -> ConditionalOrExpression
 ConditionalExpression ::= ConditionalOrExpression '?' Expression ':' ConditionalExpression
 /.$putCase consumeConditionalExpression(OperatorIds.QUESTIONCOLON) ; $break ./
+ConditionalExpression ::= ConditionalOrExpression '?' Expression ':' LambdaExpression
+/.$putCase consumeConditionalExpression(OperatorIds.QUESTIONCOLON) ; $break ./
 /:$readableName Expression:/
 
 AssignmentExpression -> ConditionalExpression
 AssignmentExpression -> Assignment
 /:$readableName Expression:/
 /:$recovery_template Identifier:/
 
-Assignment ::= PostfixExpression AssignmentOperator AssignmentExpression
+Assignment ::= PostfixExpression AssignmentOperator Expression
 /.$putCase consumeAssignment(); $break ./
 /:$readableName Assignment:/
 
@@ -2238,6 +2250,8 @@ AssignmentOperator ::= '|='
 -- has been reduced.
 Expression ::= AssignmentExpression
 /.$putCase consumeExpression(); $break ./
+Expression ::= LambdaExpression
+/.$putCase consumeExpression(); $break ./
 /:$readableName Expression:/
 /:$recovery_template Identifier:/
 
@@ -2843,6 +2857,7 @@ AssignmentExpression_NotName -> Assignment
 /:$readableName Expression:/
 
 Expression_NotName -> AssignmentExpression_NotName
+Expression_NotName -> LambdaExpression
 /:$readableName Expression:/
 -----------------------------------------------
 -- 1.5 features : end of generics
@@ -3119,3 +3134,4 @@ UNDERSCORE ::= '_'
 
 $end
 -- need a carriage return after the $end
+

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/parser/ParserBasicInformation.java

@@ -22,20 +22,20 @@ public interface ParserBasicInformation {
 
 					ERROR_SYMBOL = 138,
 					MAX_NAME_LENGTH = 41,
-					NUM_STATES = 1223,
+					NUM_STATES = 1194,
 
 					NT_OFFSET = 138,
-					SCOPE_UBOUND = 310,
-					SCOPE_SIZE = 311,
-					LA_STATE_OFFSET = 17648,
+					SCOPE_UBOUND = 320,
+					SCOPE_SIZE = 321,
+					LA_STATE_OFFSET = 17560,
 					MAX_LA = 1,
-					NUM_RULES = 926,
+					NUM_RULES = 933,
 					NUM_TERMINALS = 138,
 					NUM_NON_TERMINALS = 425,
 					NUM_SYMBOLS = 563,
-					START_STATE = 1015,
-					EOFT_SYMBOL = 39,
-					EOLT_SYMBOL = 39,
-					ACCEPT_ACTION = 17647,
-					ERROR_ACTION = 17648;
+					START_STATE = 1486,
+					EOFT_SYMBOL = 63,
+					EOLT_SYMBOL = 63,
+					ACCEPT_ACTION = 17559,
+					ERROR_ACTION = 17560;
 }

org.eclipse.jdt.core.compiler.batch/src/org/eclipse/jdt/internal/compiler/parser/TerminalToken.java

@@ -44,87 +44,87 @@ public enum TerminalToken {
 							TokenNameCOMMENT_MARKDOWN(1005),
 
 	// BEGIN_AUTOGENERATED_REGION
-							TokenNameIdentifier(22),
-							TokenNameabstract(43),
-							TokenNameassert(81),
+							TokenNameIdentifier(12),
+							TokenNameabstract(41),
+							TokenNameassert(79),
 							TokenNameboolean(104),
-							TokenNamebreak(82),
+							TokenNamebreak(80),
 							TokenNamebyte(105),
 							TokenNamecase(106),
 							TokenNamecatch(107),
 							TokenNamechar(108),
-							TokenNameclass(71),
-							TokenNamecontinue(83),
+							TokenNameclass(68),
+							TokenNamecontinue(81),
 							TokenNameconst(136),
-							TokenNamedefault(77),
-							TokenNamedo(84),
+							TokenNamedefault(74),
+							TokenNamedo(82),
 							TokenNamedouble(109),
-							TokenNameelse(119),
-							TokenNameenum(75),
+							TokenNameelse(118),
+							TokenNameenum(71),
 							TokenNameextends(92),
-							TokenNamefalse(53),
-							TokenNamefinal(44),
+							TokenNamefalse(51),
+							TokenNamefinal(42),
 							TokenNamefinally(117),
 							TokenNamefloat(110),
-							TokenNamefor(85),
+							TokenNamefor(83),
 							TokenNamegoto(137),
-							TokenNameif(86),
+							TokenNameif(84),
 							TokenNameimplements(132),
 							TokenNameimport(111),
-							TokenNameinstanceof(17),
+							TokenNameinstanceof(18),
 							TokenNameint(112),
-							TokenNameinterface(72),
+							TokenNameinterface(69),
 							TokenNamelong(113),
-							TokenNamenative(45),
-							TokenNamenew(38),
-							TokenNamenon_sealed(46),
-							TokenNamenull(54),
+							TokenNamenative(43),
+							TokenNamenew(37),
+							TokenNamenon_sealed(44),
+							TokenNamenull(52),
 							TokenNamepackage(91),
-							TokenNameprivate(47),
-							TokenNameprotected(48),
-							TokenNamepublic(49),
-							TokenNamereturn(87),
+							TokenNameprivate(45),
+							TokenNameprotected(46),
+							TokenNamepublic(47),
+							TokenNamereturn(85),
 							TokenNameshort(114),
-							TokenNamestatic(40),
-							TokenNamestrictfp(50),
-							TokenNamesuper(35),
-							TokenNameswitch(65),
-							TokenNamesynchronized(41),
-							TokenNamethis(36),
-							TokenNamethrow(79),
-							TokenNamethrows(120),
-							TokenNametransient(51),
-							TokenNametrue(55),
-							TokenNametry(88),
+							TokenNamestatic(38),
+							TokenNamestrictfp(48),
+							TokenNamesuper(33),
+							TokenNameswitch(62),
+							TokenNamesynchronized(39),
+							TokenNamethis(34),
+							TokenNamethrow(77),
+							TokenNamethrows(119),
+							TokenNametransient(49),
+							TokenNametrue(53),
+							TokenNametry(86),
 							TokenNamevoid(115),
-							TokenNamevolatile(52),
-							TokenNamewhile(80),
+							TokenNamevolatile(50),
+							TokenNamewhile(78),
 							TokenNamemodule(116),
-							TokenNameopen(121),
-							TokenNamerequires(122),
+							TokenNameopen(120),
+							TokenNamerequires(121),
 							TokenNametransitive(127),
-							TokenNameexports(123),
-							TokenNameopens(124),
+							TokenNameexports(122),
+							TokenNameopens(123),
 							TokenNameto(133),
-							TokenNameuses(125),
-							TokenNameprovides(126),
+							TokenNameuses(124),
+							TokenNameprovides(125),
 							TokenNamewith(134),
-							TokenNameIntegerLiteral(56),
-							TokenNameLongLiteral(57),
-							TokenNameFloatingPointLiteral(58),
-							TokenNameDoubleLiteral(59),
-							TokenNameCharacterLiteral(60),
-							TokenNameStringLiteral(61),
-							TokenNameTextBlock(62),
+							TokenNameIntegerLiteral(54),
+							TokenNameLongLiteral(55),
+							TokenNameFloatingPointLiteral(56),
+							TokenNameDoubleLiteral(57),
+							TokenNameCharacterLiteral(58),
+							TokenNameStringLiteral(59),
+							TokenNameTextBlock(60),
 							TokenNamePLUS_PLUS(2),
 							TokenNameMINUS_MINUS(3),
-							TokenNameEQUAL_EQUAL(19),
-							TokenNameLESS_EQUAL(12),
-							TokenNameGREATER_EQUAL(13),
-							TokenNameNOT_EQUAL(20),
-							TokenNameLEFT_SHIFT(18),
-							TokenNameRIGHT_SHIFT(14),
-							TokenNameUNSIGNED_RIGHT_SHIFT(16),
+							TokenNameEQUAL_EQUAL(21),
+							TokenNameLESS_EQUAL(14),
+							TokenNameGREATER_EQUAL(15),
+							TokenNameNOT_EQUAL(22),
+							TokenNameLEFT_SHIFT(19),
+							TokenNameRIGHT_SHIFT(13),
+							TokenNameUNSIGNED_RIGHT_SHIFT(17),
 							TokenNamePLUS_EQUAL(93),
 							TokenNameMINUS_EQUAL(94),
 							TokenNameMULTIPLY_EQUAL(95),
@@ -140,47 +140,47 @@ public enum TerminalToken {
 							TokenNameAND_AND(30),
 							TokenNamePLUS(4),
 							TokenNameMINUS(5),
-							TokenNameNOT(67),
-							TokenNameREMAINDER(9),
-							TokenNameXOR(25),
-							TokenNameAND(21),
-							TokenNameMULTIPLY(8),
+							TokenNameNOT(64),
+							TokenNameREMAINDER(10),
+							TokenNameXOR(27),
+							TokenNameAND(23),
+							TokenNameMULTIPLY(9),
 							TokenNameOR(28),
-							TokenNameTWIDDLE(68),
-							TokenNameDIVIDE(10),
-							TokenNameGREATER(15),
-							TokenNameLESS(11),
-							TokenNameLPAREN(23),
-							TokenNameRPAREN(24),
-							TokenNameLBRACE(63),
-							TokenNameRBRACE(33),
+							TokenNameTWIDDLE(65),
+							TokenNameDIVIDE(11),
+							TokenNameGREATER(16),
+							TokenNameLESS(7),
+							TokenNameLPAREN(20),
+							TokenNameRPAREN(25),
+							TokenNameLBRACE(61),
+							TokenNameRBRACE(35),
 							TokenNameLBRACKET(6),
-							TokenNameRBRACKET(70),
+							TokenNameRBRACKET(73),
 							TokenNameSEMICOLON(26),
 							TokenNameQUESTION(29),
-							TokenNameCOLON(66),
+							TokenNameCOLON(70),
 							TokenNameCOMMA(32),
 							TokenNameDOT(1),
-							TokenNameEQUAL(78),
-							TokenNameAT(37),
+							TokenNameEQUAL(76),
+							TokenNameAT(36),
 							TokenNameELLIPSIS(128),
-							TokenNameARROW(118),
-							TokenNameCOLON_COLON(7),
-							TokenNameBeginLambda(64),
-							TokenNameBeginIntersectionCast(69),
-							TokenNameBeginTypeArguments(89),
-							TokenNameElidedSemicolonAndRightBrace(73),
-							TokenNameAT308(27),
+							TokenNameARROW(126),
+							TokenNameCOLON_COLON(8),
+							TokenNameBeginLambda(75),
+							TokenNameBeginIntersectionCast(67),
+							TokenNameBeginTypeArguments(87),
+							TokenNameElidedSemicolonAndRightBrace(88),
+							TokenNameAT308(24),
 							TokenNameAT308DOTDOTDOT(135),
-							TokenNameCaseArrow(74),
+							TokenNameCaseArrow(89),
 							TokenNameRestrictedIdentifierYield(90),
-							TokenNameRestrictedIdentifierrecord(76),
-							TokenNameRestrictedIdentifiersealed(42),
+							TokenNameRestrictedIdentifierrecord(72),
+							TokenNameRestrictedIdentifiersealed(40),
 							TokenNameRestrictedIdentifierpermits(129),
 							TokenNameBeginCasePattern(130),
 							TokenNameRestrictedIdentifierWhen(131),
-							TokenNameUNDERSCORE(34),
-							TokenNameEOF(39),
+							TokenNameUNDERSCORE(66),
+							TokenNameEOF(63),
 							TokenNameERROR(138);
 
 // END_AUTOGENERATED_REGION

org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/ExpressionContextTests.java

@@ -106,13 +106,8 @@ public void test003() {
 			"----------\n" +
 			"1. ERROR in X.java (at line 10)\n" +
 			"	Object p = (int & I & J) () -> {};\n" +
-			"	            ^^^\n" +
-			"Base types are not allowed in intersection cast operator\n" +
-			"----------\n" +
-			"2. ERROR in X.java (at line 10)\n" +
-			"	Object p = (int & I & J) () -> {};\n" +
-			"	                         ^^^^^\n" +
-			"The target type of this expression must be a functional interface\n" +
+			"	           ^^^^^^^^^^^^^\n" +
+			"Syntax error on token(s), misplaced construct(s)\n" +
 			"----------\n");
 }
 // https://bugs.eclipse.org/bugs/show_bug.cgi?id=399773, [1.8][compiler] Cast expression should allow for additional bounds to form intersection types
@@ -613,8 +608,8 @@ public void test021() {
 			"----------\n" +
 			"1. ERROR in X.java (at line 6)\n" +
 			"	return \"Hello\" + () -> {};\n" +
-			"	                 ^^^^^\n" +
-			"The target type of this expression must be a functional interface\n" +
+			"	               ^\n" +
+			"Syntax error on token \"+\", invalid AssignmentOperator\n" +
 			"----------\n" +
 			"2. ERROR in X.java (at line 9)\n" +
 			"	return \"Hello\" + (I)(() -> {});\n" +

org.eclipse.jdt.core.tests.compiler/src/org/eclipse/jdt/core/tests/compiler/regression/LambdaExpressionsTest.java

@@ -8989,6 +8989,30 @@ public static void main(String[] args) {
 			},
 			"class X$A");
 }
+public void testLambdaAsAssignmentRHS() {
+	this.runConformTest(
+			new String[] {
+				"X.java",
+				"""
+				import java.util.function.Consumer;
+
+				public class X {
+					Consumer<Boolean> xx;
+					void foo() {
+						this.xx = (f) -> { System.out.println(f); };
+						this.xx.accept(true);
+						this.xx.accept(false);
+						this.xx.accept(true);
+					}
+					public static void main(String [] args) {
+                        new X().foo();
+                    }
+				}
+				""",
+			},
+			"true\nfalse\ntrue"
+			);
+}
 public static Class testClass() {
 	return LambdaExpressionsTest.class;
 }