Fix compilation of SpEL Elvis with primitive operands

spring-expression/src/main/java/org/springframework/expression/spel/ast/Elvis.java

@@ -128,12 +128,19 @@ public void generateCode(MethodVisitor mv, CodeFlow cf) {
 		this.children[0].generateCode(mv, cf);
 		String lastDesc = cf.lastDescriptor();
 		Assert.state(lastDesc != null, "No last descriptor");
+		if (CodeFlow.isPrimitive(lastDesc) && !"V".equals(lastDesc)) {
+			// A primitive value is neither null nor an empty String, so the value
+			// of the expression is always the value of the left-hand operand.
+			if (!CodeFlow.isPrimitive(this.exitTypeDescriptor)) {
+				CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
+			}
+			cf.exitCompilationScope();
+			cf.pushDescriptor(this.exitTypeDescriptor);
+			return;
+		}
 		if ("Ljava/util/Optional".equals(lastDesc)) {
 			CodeFlow.insertOptionalUnwrapIfNecessary(mv, lastDesc);
 		}
-		else {
-			CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
-		}
 		cf.exitCompilationScope();
 
 		mv.visitInsn(DUP);

spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java

@@ -6758,6 +6758,41 @@ void elvisMiscellaneous() {
 			assertIsCompiled(exp);
 		}
 
+		@Test
+		void elvisWithPrimitiveOperandsOfSameType() {
+			expression = parser.parseExpression("3 ?: 4");
+			assertThat(expression.getValue()).isEqualTo(3);
+			assertCanCompile(expression);
+			assertThat(expression.getValue()).isEqualTo(3);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("I");
+
+			// double slot primitive
+			expression = parser.parseExpression("3L ?: 4L");
+			assertThat(expression.getValue()).isEqualTo(3L);
+			assertCanCompile(expression);
+			assertThat(expression.getValue()).isEqualTo(3L);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("J");
+
+			expression = parser.parseExpression("3.5d ?: 4.5d");
+			assertThat(expression.getValue()).isEqualTo(3.5d);
+			assertCanCompile(expression);
+			assertThat(expression.getValue()).isEqualTo(3.5d);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("D");
+
+			expression = parser.parseExpression("true ?: false");
+			assertThat(expression.getValue()).isEqualTo(true);
+			assertCanCompile(expression);
+			assertThat(expression.getValue()).isEqualTo(true);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Z");
+
+			// method returning primitive
+			expression = parser.parseExpression("length() ?: 0");
+			assertThat(expression.getValue("abc")).isEqualTo(3);
+			assertCanCompile(expression);
+			assertThat(expression.getValue("abc")).isEqualTo(3);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("I");
+		}
+
 		@Test
 		void elvis_SPR17214() {
 			SpelParserConfiguration spc = SpelParserConfiguration.builder().compilerMode(SpelCompilerMode.IMMEDIATE).build();