Don't parse __autoconcat__ to sconcat in strict mode

Parse `__autoconcat__()` to the new `__statements__()` instead of `sconcat()` in strict mode. `__statements__()` takes arguments of any type and returns `void` for typechecking, so compile errors will be generated in cases where `__autoconcat__()` used to insert `sconcat()`s, or in other words, where the user has either forgotten to put some `.` concat, or where the user has made a mistake.
This change does not affect non-strict mode, as automatically inserting concats is a feature there.
Alias syntax should also remain possible in strict mode, but only when the whole alias is nicely concatenated together by the user. Inserting multiple arguments/statements will cause the code block to be interpreted as a statements block and not as an alias redirect.

src/main/java/com/laytonsmith/core/MethodScriptCompiler.java

@@ -2119,9 +2119,13 @@ private static void rewriteAutoconcats(ParseTree root, Environment env,
 			}
 		}
 		if(root.getData() instanceof CFunction && root.getData().val().equals(__autoconcat__.NAME)) {
+
+			// In non-strict mode, let __autoconcat__ glue arguments together with sconcat.
+			boolean returnSConcat = !root.getFileOptions().isStrict();
+
 			try {
 				ParseTree ret = ((Compiler.__autoconcat__) ((CFunction) root.getData()).getFunction())
-						.rewrite(root.getChildren(), true, envs);
+						.rewrite(root.getChildren(), returnSConcat, envs);
 				root.setData(ret.getData());
 				root.setChildren(ret.getChildren());
 			} catch (ConfigCompileException ex) {

src/main/java/com/laytonsmith/core/compiler/OptimizerObject.java

@@ -45,7 +45,11 @@ private void optimize01(ParseTree tree, CompilerEnvironment compilerEnvironment)
 				= (com.laytonsmith.core.functions.Compiler.__autoconcat__)
 				FunctionList.getFunction("__autoconcat__", null, Target.UNKNOWN);
 		if(tree.getData() instanceof CFunction && tree.getData().val().equals("__autoconcat__")) {
-			ParseTree tempNode = autoconcat.rewrite(tree.getChildren(), true, null);
+
+			// In non-strict mode, let __autoconcat__ glue arguments together with sconcat.
+			boolean returnSConcat = !tree.getFileOptions().isStrict();
+
+			ParseTree tempNode = autoconcat.rewrite(tree.getChildren(), returnSConcat, null);
 			tree.setData(tempNode.getData());
 			tree.setChildren(tempNode.getChildren());
 		}

src/main/java/com/laytonsmith/core/functions/Compiler.java

@@ -152,9 +152,10 @@ public String docs() {
 		 * this __autoconcat__ node being replaced or in a compile error if the __autoconcat__ cannot be converted to
 		 * an executable AST node. This being a function is merely a convenient way to defer processing until after
 		 * parsing, meaning that it should ALWAYS be rewritten before executing the AST.
-		 *
-		 * @param list
-		 * @param returnSConcat
+		 * @param list - A list containing all {@link ParseTree} children of this __autoconcat__.
+		 * @param returnSConcat - If parsing results in only one child function, then this argument is ignored.
+		 * If {@code true}, the resulting parsed functions will be wrapped into {@link sconcat}.
+		 * If {@code false}, the resulting parsed functions will be wrapped into {@link __statements__}.
 		 * @return The executable AST node, representing the code/tokens in this __autoconcat__.
 		 * @throws ConfigCompileException If this __autoconcat__ cannot be converted to an executable AST node.
 		 */
@@ -547,14 +548,48 @@ public ParseTree rewrite(List<ParseTree> list, boolean returnSConcat,
 				if(returnSConcat) {
 					tree = new ParseTree(new CFunction(sconcat.NAME, t), options);
 				} else {
-					tree = new ParseTree(new CFunction(concat.NAME, t), options);
+					tree = new ParseTree(new CFunction(__statements__.NAME, t), options);
 				}
 				tree.setChildren(list);
 				return tree;
 			}
 		}
 	}
 
+	@api
+	@noprofile
+	@hide("This is only used internally by the compiler.")
+	public static class __statements__ extends DummyFunction {
+
+		public static final String NAME = "__statements__";
+
+		@Override
+		public String getName() {
+			return NAME;
+		}
+
+		@Override
+		public String docs() {
+			return "void {[...]} Used internally by the compiler. You shouldn't use it.";
+		}
+
+		@Override
+		public Mixed exec(Target t, Environment env, Mixed... args) throws ConfigRuntimeException {
+			return CVoid.VOID;
+		}
+
+		@Override
+		public CClassType getReturnType(Target t, List<CClassType> argTypes,
+				List<Target> argTargets, Environment env, Set<ConfigCompileException> exceptions) {
+			return CVoid.TYPE;
+		}
+
+		@Override
+		public boolean preResolveVariables() {
+			return false;
+		}
+	}
+
 	@api
 	@hide("This is only used for testing unexpected error handling.")
 	@noboilerplate

src/main/java/com/laytonsmith/core/functions/ControlFlow.java

@@ -45,6 +45,7 @@
 import com.laytonsmith.core.exceptions.CRE.CRERangeException;
 import com.laytonsmith.core.exceptions.CRE.CREThrowable;
 import com.laytonsmith.core.functions.BasicLogic.and;
+import com.laytonsmith.core.functions.Compiler.__statements__;
 import com.laytonsmith.core.functions.Compiler.centry;
 import com.laytonsmith.core.functions.DataHandling.assign;
 import com.laytonsmith.core.functions.Math.dec;
@@ -647,7 +648,8 @@ public ParseTree postParseRewrite(ParseTree ast, Environment env,
 			List<ParseTree> children = ast.getChildren();
 			Target t = ast.getTarget();
 			if(children.size() > 1 && children.get(1).getData() instanceof CFunction
-					&& new StringHandling.sconcat().getName().equals(children.get(1).getData().val())) {
+					&& (sconcat.NAME.equals(children.get(1).getData().val())
+							|| __statements__.NAME.equals(children.get(1).getData().val()))) {
 				//This is the brace/case/default usage of switch, probably. We need
 				//to refactor the data into the old switch format.
 				List<ParseTree> newChildren = new ArrayList<>();
@@ -745,7 +747,7 @@ public ParseTree postParseRewrite(ParseTree ast, Environment env,
 					newChildren.add(new ParseTree(conditions, children.get(0).getFileOptions()));
 				}
 				if(lastCodeBlock.size() > 0) {
-					ParseTree codeBlock = new ParseTree(new CFunction(new StringHandling.sconcat().getName(), t),
+					ParseTree codeBlock = new ParseTree(new CFunction(sconcat.NAME, t),
 							lastCodeBlock.get(0).getFileOptions());
 					for(ParseTree line : lastCodeBlock) {
 						codeBlock.addChild(line);