Support compilation of map indexing with primitive in SpEL

Prior to this commit, the Spring Expression Language (SpEL) failed to
compile an expression that indexed into a Map using a primitive literal
(boolean, int, long, float, or double).

This commit adds support for compilation of such expressions by
ensuring that primitive literals are boxed into their corresponding
wrapper types in the compiled bytecode.

Closes gh-32903

(cherry picked from commit aed1d5f)

Author: sbrannen

Diff for: spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java

@@ -285,9 +285,7 @@ else if (this.indexedType == IndexedType.MAP) {
 				mv.visitLdcInsn(mapKeyName);
 			}
 			else {
-				cf.enterCompilationScope();
-				index.generateCode(mv, cf);
-				cf.exitCompilationScope();
+				generateIndexCode(mv, cf, index, Object.class);
 			}
 			mv.visitMethodInsn(
 					INVOKEINTERFACE, "java/util/Map", "get", "(Ljava/lang/Object;)Ljava/lang/Object;", true);

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

@@ -552,6 +552,52 @@ void indexIntoListUsingIntegerWrapper() {
 			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
 		}
 
+		@Test  // gh-32903
+		void indexIntoMapUsingPrimitiveLiteral() {
+			Map<Object, String> map = new HashMap<>();
+			map.put(false, "0");    // BooleanLiteral
+			map.put(1, "ABC");      // IntLiteral
+			map.put(2L, "XYZ");     // LongLiteral
+			map.put(9.99F, "~10");  // FloatLiteral
+			map.put(3.14159, "PI"); // RealLiteral
+			context.setVariable("map", map);
+
+			// BooleanLiteral
+			expression = parser.parseExpression("#map[false]");
+			assertThat(expression.getValue(context)).isEqualTo("0");
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo("0");
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
+
+			// IntLiteral
+			expression = parser.parseExpression("#map[1]");
+			assertThat(expression.getValue(context)).isEqualTo("ABC");
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo("ABC");
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
+
+			// LongLiteral
+			expression = parser.parseExpression("#map[2L]");
+			assertThat(expression.getValue(context)).isEqualTo("XYZ");
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo("XYZ");
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
+
+			// FloatLiteral
+			expression = parser.parseExpression("#map[9.99F]");
+			assertThat(expression.getValue(context)).isEqualTo("~10");
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo("~10");
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
+
+			// RealLiteral
+			expression = parser.parseExpression("#map[3.14159]");
+			assertThat(expression.getValue(context)).isEqualTo("PI");
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo("PI");
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
+		}
+
 		private String stringify(Object object) {
 			Stream<? extends Object> stream;
 			if (object instanceof Collection) {