evalString

 string evalString(Expression e) in {
        // FIXME: newtype
        // assert(cast(SliceType) peelAlias(e.type).type, "this only CTFE strings.");
    } body {
        import std.stdio;

        // Create a global variable that recieve the string.
        auto stringType = codeGen.visit(e.type);
        auto receiver = LLVMAddGlobal(codeGen.dmodule, stringType, "__ctString");
        scope(exit) LLVMDeleteGlobal(receiver);

        writeln("---1");

        LLVMValueRef[2] constInit = [ LLVMConstInt( LLVMInt64TypeInContext( codeGen.llvmCtx), 0, false),
            LLVMConstNull( LLVMPointerType (LLVMInt8TypeInContext(codeGen.llvmCtx),0)) ];
        LLVMDumpValue(LLVMGetUndef(stringType));
        LLVMDumpValue(LLVMConstStruct( constInit.ptr, 2, false ));
        LLVMDumpValue(receiver);
        LLVMSetInitializer(receiver, LLVMConstStructInContext( codeGen.llvmCtx, constInit.ptr, 2, false ));
        LLVMDumpValue(receiver);
        writeln("---2");

        LLVMTypeRef[1] paramTypes = [LLVMInt8TypeInContext(codeGen.llvmCtx)];
        writeln("---2.2");

        auto funType = LLVMFunctionType(LLVMVoidTypeInContext(codeGen.llvmCtx), paramTypes.ptr, 1, false);
        writeln("---3");

        auto fun = LLVMAddFunction(codeGen.dmodule, "__ctfe", funType);
        scope(exit) LLVMDeleteFunction(fun);
        writeln("---4");

        auto backupCurrentBB = LLVMGetInsertBlock(codeGen.builder);
        scope(exit) {
            if(backupCurrentBB) {
                LLVMPositionBuilderAtEnd(codeGen.builder, backupCurrentBB);
            } else {
                LLVMClearInsertionPosition(codeGen.builder);
            }
        }

        auto bodyBB = LLVMAppendBasicBlockInContext(codeGen.llvmCtx, fun, "");
        LLVMPositionBuilderAtEnd(codeGen.builder, bodyBB);

        // Generate function's body.
        import d.llvm.expression;
        auto eg = ExpressionGen(codeGen);


        writeln("---11");
        auto castToPointer = LLVMBuildPointerCast(codeGen.builder,
            LLVMGetFirstParam(fun),
            LLVMPointerType(LLVMInt8TypeInContext(codeGen.llvmCtx), 0), "");
        writeln("---12");

        auto casted = LLVMBuildPointerCast(codeGen.builder,
            castToPointer,
            LLVMPointerType(stringType,0), "");
        writeln("---22");
        LLVMBuildStore(codeGen.builder, eg.visit(e), casted);
        writeln("---33");
        LLVMBuildRetVoid(codeGen.builder);
        writeln("---4");

        codeGen.checkModule(codeGen.dmodule);
        import std.stdio;

        auto jitModule = LLVMCloneModule( codeGen.dmodule );
        //scope(exit) LLVMDisposeModule(jitModule);
        //scope(failure) LLVMDumpModule(jitModule);
        auto executionEngine = createExecutionEngine(jitModule);
        //scope(exit) LLVMDisposeExecutionEngine(executionEngine);

        auto jitFun = LLVMGetNamedFunction(jitModule, "__ctfe");
        LLVMDumpValue(jitFun);

        string foo;
        auto ret = LLVMRunFunction(executionEngine, jitFun, 1,
            [LLVMCreateGenericValueOfInt(LLVMInt8TypeInContext(codeGen.llvmCtx), cast(uint)cast(void*)&foo, false)].ptr);
        writeln("\"",foo, "\"");
        return foo.idup; //return s.idup;
    }